The image above shows two DDR2 RAM memory modules, with heat spreaders fitted, installed in two of four DIMM memory slots of a desktop PC motherboard.
RAM is an acronym for Random Access Memory that is also known as volatile memory, because the data it holds is lost when the desktop PC or laptop/notebook computer using it is switched off. Briefly, RAM memory is used by the system to store data in the form of files for processing by a computer's central processing unit (CPU), also known as the processor.
That said, computers can make use of technology called DMA (Direct Memory Access) to bypass the processor: "Direct memory access" (DMA) is a feature of modern computers and microprocessors that allows certain hardware subsystems within the computer to access system memory for reading and/or writing independently of the central processing unit. Many hardware systems use DMA including disk drive controllers, graphics cards, network cards and sound cards."
The processors used in most PCs are made by Intel and AMD. The processor runs the program and data files according to instructions given to it by the operating system, which, on PCs, is usually a version of Windows, or, to a much lesser extent, a version of Linux.
The amount of RAM memory used in modern desktop and laptop computers is expressed in megabytes (MB) and gigabytes(GB). A gigabyte (1GB) is 1024MB. Most desktop and laptop computers that came with Windows XP preinstalled came with 512MB. However, this increased to gigabytes when Windows Vista was released in January 2007. A computer with Windows Vista preinstalled should have a minimum of 2GB or RAM memory to run comfortably, however, 1GB of RAM memory in computers running a 32-bit version of Windows 7 should suffice, because the 32-bit versions of Windows 7 can run on a comparatively low-spec netbook computer, most of which currently only have 1GB of memory (January 2010).
32-bit versions of Windows cannot use more than about 3.5GB of memory; 64-bit versions of Windows can support far more memory than most home users require. However, up to 4GB of memory, the 64-bit versions require twice as much memory as the 32-bit versions, so the minimum a 64-bit version should have is 2GB for Windows 7 and 4GB for Windows Vista. Most computers in use currently use a 32-bit version of Windows.
Note also that even with a 64-bit processor and a 64-bit version of Windows XP/Vista/Windows 7, the motherboard's chipset must support at least 8GB of address space and the system's BIOS setup programust support memory remapping. Read this Q&A on this website for more information on those requirements: My computer running the 64-nit version Windows 7 Home Premium isn't using all its 4GB RAM memory.
To find out which bit version of Windows you have, in Windows XP go Start => Control Panel and look for System and look on the General tab of the System Properties window. In Windows Vista choose the Classic View in the Control Panel. In Windows 7, just enter the word system in the Start => Search programs and files box to be provided with a clickable link to the System Properties window.
RAM memory that is not recognized or only half or a quarter of it is recognized
Computer users are constantly complaining in newsgroups that they have purchased RAM that is not recognised at all by their computers, or is recognised as only a half, or even a quarter of its actual capacity. Usually, the RAM is not at fault, but is just incompatible with the computer's motherboard.
The problem arises because new types of RAM modules are introduced, and the older motherboard chipsets are not designed to recognise them.
A particular motherboard will have been designed to run the range of RAM modules that were on the market when it was released, but its manufacturer cannot anticipate changes in technology in its design, consequently the motherboard's manual will only list the types of RAM that the motherboard supports at the time it was made available.
Unfortunately, very few motherboard manufacturers update their manuals to report incompatibilities with types of RAM modules that were not available when the motherboard was released.
That is why you are advised to try using the relevant Crucial Memory Advisor in order to make sure that you don't purchase RAM that isn't supported by your brand-name desktop or laptop computer or the computer's motherboard. Indeed, if you're contemplating buying a new motherboard for a desktop PC, it would be a good idea to find out if it is listed by Crucial (or will be listed) before you buy it.
The US and UK Memory Advisors (below) allow you to find out what types of RAM are available for your laptop/notebook/netbook computer, brand-name PC, or motherboard - and what the current prices are in the USA and the UK.
For example, if your computer has an Asus motherboard, open the menu, scroll down to Asus, and click GO. If, say, you have a Dell computer, scroll down to DELL, and do likewise. You will be taken to the relevant information on Crucial's website. Using MSI (Microstar) as an example, because it manufactures all kinds of computer equipment, on Crucial's website, you will have to choose which MSI product you require memory for - a motherboard, a desktop PC, or a laptop computer.
If a particular manufacturer isn't listed in the UK Memory Advisor, try looking for it in the US Memory Advisor, and vice versa. All you have to do is find out what the reference number is for a particular type and memory size of RAM that the system or motherboard supports and then order it from the US or UK site. Both sites will be able to supply all of the different kinds of RAM that Crucial sells, but one site might not list a particular make and model of computer or motherboard that the other site does list.
If you don't know the make and model of the motherboard installed in your computer, here is a good free utility - Belarc Advisor - that creates an analysis of the hardware and software on a personal computer. Look under FREE DOWNLOAD - http://www.belarc.com/. Another free utility that also provides detailed information on the memory itself is CPU-Z.
Crucial's UK and US Memory Advisors
Paul Mullen, was the highly-respected computer guru of the Helpfile at ComputerShopper.co.uk - "I have recently been buying my memory only from Crucial Technology. I would rather pay the extra cost than waste time trying to track down the obscure program faults that bad memory can cause."
How to find out if a Windows XP, Windows Vista or Windows 7 computer is running a 32-bit or 64-bit versionTo find out if a Windows XP computer is 32-bit or 64-bit, click the Start button and then click Run. Type winmsd.exe, and then click OK. When System Summary is selected in the navigation pane, locate Processor under Item in the details window pane. If the value that corresponds to Processor starts with x86, the computer is running a 32-bit version of Windows. If the value that corresponds to Processor starts with ia64 or AMD64, the computer is running a 64-bit version of Windows. To find out if a Windows Vista computer is running 32-bit or 64-bit Windows, do the following: 1. - Open System by clicking the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking System. 2. - Under System, you can view the system type. In Windows 7, it is in the Control Panel under System and security when View by: Categories is being used. If you view by large or small icons the Control Panel items are listed individually. More information on 32-bit and 64-bit Windows and 32-bit and 64-bit processors is provided further down in this article. |
Windows 7 is the latest version of Windows. Home users were able to buy the version of their choice on 22 October 2009. Most netbook computers are presently running Windows XP because Windows Vista runs very slowly on their relatively low specifications of memory and processor, but Windows 7 runs well on them because of its lower hardware requirements. To such a extent that Microsoft will not be creating a netbook version of Windows Vista.
There have been many different types of RAM memory in use since it first was used in computers. The RAM memory used in current PCs comes in the form of DDR and DDR2 and DDR3 memory modules. The correct type that the computer's motherboard supports has to be used. Some motherboards can support two types, such as DDR and DRR2, but most motherboards only support one type. A kit consisting of two 1GB modules of DDR2 memory, for use in a desktop PC, made by Crucial, is shown below. The upper side with the notch and the metallic edge is keyed to fit into the appropriate memory (DIMM) slot, therefore it cannot be installed in the wrong type of slot unless the installer uses the kind of force that will probably destroy the module.
Unless all of the memory slots on a computer's motherboard are already fitted with memory modules, the RAM memory in most desktop and laptops computers can be increased by installing more memory (upgrading the memory). Installing one or more additional memory modules in a desktop or a laptop computer is a simple process that is dealt with at the top of Page 2 of this article.
Some high-speed RAM memory modules come with passive heatsinks fitted to them that keep them cool. These heatsinks can also be purchased and replaced. Names for memory-cooling devices are heatspreaders, heat spreaders, ramsinks, memory cooling kits, RAM heat sinks, etc. You can find vendors for them by entering these names in the Google search box at the top of this page (with its Web radio button enabled).
The image below is of a Corsair memory module with a passive heatsink fitted to it.
How To Replace Memory Heat Spreaders -
Most of the current desktop PCs and laptop PCs have motherboards that use DDR or DDR2 memory. However, DDR3 memory is now available, so, as time goes on, more motherboards will be using it.
The latest Intel Socket LGA1366 quad-core Core i7 processors (CPUs) can only run on DDR3 memory (Socket LGA1366 motherboards require DDR3 memory and Core i7 processors can only run on Socket LGA1366 motherboards).
The latest AMD Phenom II quad-core and triple-core processors can use DDR3 memory when installed in a Socket AM3 motherboard and DDR2 memory when installed in a Socket AM2+ motherboard. (They can be used with both Socket AM2+ and Socket AM3 motherboards.)
The modules are installed in the DIMM memory slots on the PC's motherboard. Most desktop-PC motherboards provide four DIMM slots, but some micro-ATX motherboards only have two slots, both of which must be filled if the memory is used in the fastest dual-channel mode.
Note that most laptop PCs only have two memory slots, so you can add additional memory if one of the slots are free. If both slots have memory modules installed in them, to increase the amount of memory you will have to remove one or both modules and install modules with a higher capacity. How much memory a laptop supports and where it is installed is information provided in its user manual, which should be available as a download from its manufacturer's website if you don't have a copy.
MSI K8N Diamond Plus Socket 939 desktop-PC motherboard, shown above, has four DIMM slots that are in the bottom right hand side of the board (when the connection ports can be seen at the top of the board). On this motherboard, the slots are alternatively coloured blue and teal green to make it easier to install the modules in dual-channel or single-channel modes, the instructions for which are provided in the motherboard's user manual that comes with it, or which can be downloaded from MSI's website.
When updgrading memory, it is essential that you purchase the right type of memory module, because DDR, DDR2, and DDR3 memory is incompatible with each other. You cannot use a DDR2 module in a DDR DIMM slot, etc. However, some motherboards can have slots for both DDR/DDR2 or DDR2/DDR3 modules. No motherboards support all three types. A DDR3-supporting motherboard will not support DDR memory, but it might, but not necessarily, support DDR2 memory. The motherboard's manual or the PC's user guide should provide the information required to be able to tell which type of slots are provided.
If you don't have a copy of the manual, you should be able to download one in the PDF format from the manufacturer's website. You can use a tool called CPU-Z to find out the make/model of the motherboard as well as the type of memory installed, the size of the module(s), and which modules are installed in which slots. Note that a PDF reader, such as the free Foxit Reader is required to read PDF documents.
Most DDR/DDR2/DDR3 memory comes in matched pairs of modules to take advantage of dual-channel mode (or triple-channel mode with DDR3 installed in Socket LGA1366 motherboards that run Intel's new Core i7 quad-core processors).
Modern AMD-based motherboards (motherboards that run processors made by AMD) have a dual-channel memory bus, which makes it possible for pairs of modules to have a performance advantage compared to using a single module of the same size. In other words, two 1GB modules in dual-channel mode can be accessed as if they were a single module and outperform a single 2GB module that can only operate in single-channel mode.
Now, with the arrival of DDR3 memory and Intel's Core i7 processors that run on Socket LGA1366 motherboards, for the first time, Intel has a range of processors with an inbuilt memory controller that can run memory in triple-channel mode (three memory modules that can be accessed at the same time as if a single module). When two memory modules are installed, the triple-channel architecture operates in dual-channel mode.
You can make use of the UK and US Crucial Memory Advisors provided further down this page that provide RAM memory on a brand-name desktop or laptop PC or motherboard basis. By making use of the applicable advisor, as long as you identify your computer's make/model or its make/model of motherboard, you are guaranteed to obtain the correct memory for your computer or you get your money back.
Intel's new Core i7 quad-core processors can use triple-channel modeUntil the Socket LGA1366 Intel Core i7 quad-core processors first became available in November 2008, only AMD's Athlon 64 (single-core and dual-core) and Phenom (quad-core) processors could use dual-channel mode, because it requires the memory controller to be built into the processor, and Intel's processors did not provide that feature. Dual-channel mode requires two memory modules to be used in tandem. If the motherboard has four DIMM memory slots, it can run two pairs in tandem in dual-channel mode. But now the Core i7 processors also have an built-in memory controller. Core i7 is Intel's first platform to use only DDR3 RAM memory. Moreover, it uses a built-in triple-channel memory controller, so DDR3 DIMM modules will soon be available in packs of three to make use of the six DIMM memory slots that Socket LGA1366 motherboards have in order to use triple-channel mode. The first Socket LGA1366 motherboards, such as the MSI MS-7522 motherboard, that run the Core i7 processors, provide six memory slots. The motherboard's user manual shows which slot can be used for a single memory module, and which slots can be used for dual-channel and triple-channel mode. If all six slots are filled with identical modules, you will have two sets of modules running in triple-channel mode. As with dual-channel mode, triple-channel mode provides a small gain in performance. Intel Core i7 - http://www.pcpro.co.uk/reviews/233892/intel-core-i7.html |
Adding additional memory requires making use of free DIMM slots, so, if you are buying a brand-name PC, it is advisable to find out if additional memory can be installed. This is advisable because the amount of memory used by Microsoft's Windows operating system has been increasing with each new version since Windows 95 and Windows 98, which could run comfortably on 32MB and 64MB respectively, which at that time was a huge amount of memory, but which Windows XP could not run on.
A computer running Windows XP Home Edition that doesn't run memory-hungry applications, such as video-editing software, should have minimum of 512MB of RAM memory to run comfortably. Such a computer will run ordinary office applications, etc., with 256MB of memory, but slowly. Motherboard user manuals recommend that the 32-bit versions of Windows XP Home (which is only available as a 32-bit version) and Professional Editions (which has both 32-bit and 64-bit versions) should have no more than 3.5GB of memory installed, because they don't support more than that amount of memory. The 64-bit version of Windows XP Professional (Windows XP Professional x64 Edition) supports up to 128 gigabytes (GB) of RAM and 16 terabytes of virtual (swap-file) memory on the computer's hard disk drive.
Most of the versions of Windows Vista require more RAM memory to run optimally (on a computer that doesn't use memory-hungry applications) than Windows XP. A video-editing application is an example of memory-intensive software. Only Windows Vista Home Basic has a recommended minimum amount of memory of 512MB, which is the same minimal amount recommended for Windows XP. Windows Vista Home Premium, the most popular version, and Windows Vista Ultimate require a minimum of 1GB (1024MB) of memory, which is twice the minimal amount of memory recommended to run Windows XP. A 32-bit version of Windows XP/Vista cannot use more than 3.5GB of memory, but you can install 4GB. Any more than that will slow the computer down.
See the table further down this page for the memory requirements of Windows 7.
If you want to install more than 4GB of RAM memory and have Windows support it, the computer must have a 64-bit processor, which almost all new computers now have, and be running a 64-bit version of Windows that supports more than 4GB. To be a 64-bit system, a computer must also be running a 64-bit operating system, which could be the latest versions of Linux, or the 64-bit versions of Windows XP Professional (XP Home Edition only comes as a 32-bit version), or the 64-bit versions of Windows Vista, which are:
Windows Vista Enterprise 64-bit edition; Windows Vista Home Basic 64-bit edition; Windows Vista Home Premium 64-bit edition; Windows Vista Ultimate 64-bit edition; Windows Vista Business 64-bit edition
64-bit Editions of Windows Vista -
http://www.microsoft.com/windows/products/windowsvista/editions/64bit.mspx
The 32-bit versions of Windows XP and Windows Vista support up to 4GB of RAM, but can only use about 3.5GB in practice. However, most of the 64-bit versions of Windows Vista support a huge 128GB of RAM, which cannot be installed on current motherboards because only 8GB DIMM modules are currently available, with 16GB modules on the way, and even motherboards that support Intel Core i7 quad-core processors only have six DIMM memory slots.
Memory maximums for the different versions of Windows:
Windows XP Home 32-bit: 4GB - Windows XP Professional 32-bit: 4GB - Windows XP Professional 64-bit: 128GB - Windows Vista Home Basic 32-bit: 4GB - Windows Vista Home Basic 64-bit: 8GB - Windows Vista Home Premium 32-bit: 4GB - Windows Vista Home Premium 64-bit: 16GB - Windows Vista Ultimate 32-bit: 4GB - Windows Vista Ultimate 64-bit: 128GB+ - Windows Vista 32-bit: 4GB - Windows Vista 64-bit: 128GB+
This page provides the details for all of the current versions of Windows, including Windows 7:
Memory Limits for Windows Releases -
http://msdn.microsoft.com/en-us/library/aa366778(VS.85).aspx
Memory Limits: Windows 7:
| Windows 7 Starter | ||
| Windows 7 Home Basic | ||
| Windows 7 Home Premium | ||
| Windows 7 Professional | ||
| Windows 7 Enterprise | ||
| Windows 7 Ultimate |
This article explains how the current versions of Windows use memory and how you can increase the memory limits:
Access more memory, even on a 32-bit system -
http://windowssecrets.com/2008/12/18/03...
You can find out if a particular Intel or AMD processor is 32-bit or 64-bit on the following two pages:
Desktop CPU Comparison Guide - AMD processors -
http://www.techarp.com/showarticle.aspx?artno=337&pgno=0
Desktop CPU Comparison Guide - Intel processors -
http://www.techarp.com/showarticle.aspx?artno=337&pgno=4
Vista Workshop – Performance Boost with 8GB of RAM -
"In order to be able to utilize the entire [8GB of] system memory, you will therefore need to use a 64 bit version of Windows Vista. In this article, we will take a look at memory usage under the 32 and 64 bit versions of Windows Vista and analyze how the operating system behaves with different amounts of RAM." -
http://www.tomshardware.co.uk/Microsoft-Windows-Vista,review-30272.html
Note well that the 32-bit versions of Windows Vista will recognise less than 4GB of memory unless the computer meets certain requirements.
"How much memory your Windows OS will recognize depends on which version of Windows you are running. 32-bit versions of Windows will see (and utilize) only 3GB or 3.5GB. To utilize more memory, install a 64-bit version of your OS. More information about OS memory maximums can be found at http://www.crucial.com/kb/answer.aspx?qid=4251."
Read this MS Knowledge Base article for more information:
The system memory that is reported in the System Information dialog box in [a 32-bit version of] Windows Vista is less than you expect if 4 GB of RAM is installed -
http://support.microsoft.com/kb/929605
Pushing the Limits of Windows: Physical Memory -
http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx
Read this Q&A on this site for more information on Vista's RAM requirements: The memory requirements of Windows Vista: How much RAM memory does Windows Vista really need to run optimally?
Kingston Technology - Ultimate Memory Guide -
Covers Windows Vista, Windows XP, Windows 2000, Windows 98, Linux, and Macintosh OS X. - http://www.kingston.com/tools/umg/umg01b.asp
Buying a new PC? 'Windows Vista Capable' barely hits the mark - IBM'er says Vista's RAM sweet spot is 4GB -
http://www.computerworld.com/action/...articleId=9011523&intsrc=hm_list
Note that the way in which Windows Vista uses virtual memory, which simulates RAM memory by using storage space on a PC's hard disk drive when actual memory runs low, has been improved.
Windows Vista: SuperFetch and External Memory Devices -
"Windows Vista sports a new memory performance enhancement system called SuperFetch and a new way to extend the virtual memory by way of External Memory Devices (EMD)." - http://articles.techrepublic.com.com/5100-10877_11-6039379.html?tag=nl.e132
For more information on this subject, read Windows Vista recommended system requirements.
After Windows Vista was released, most of the current desktop PCs and laptop/notebook computers that were being sold new with Windows XP came with 1GB of RAM memory in anticipation of being upgraded to Windows Vista Home Premium or Windows Vista Ultimate.
Visit the Using Windows Vista section of this website for more information on those versions of Windows.
Visit the Windows 7 section of this website for more information on those versions (the latest) of windows.
Fortunately, upgrading a deskop or laptop computer's RAM is a relatively easy matter provided that the computer has one or more spare DIMM/SO-DIMM memory slots on its motherboard and you obtain the correct kind of DIMM module(s) for a desktop PC and SO-DIMM module(s) for a laptop PC.
If a desktop computer's motherboard only has two DIMM memory slots that each have a 512MB module installed in it, making a total of 1024MB (1GB) of memory, you can still upgrade the system to 2GB of memory if the motherboard supports 1GB modules in each slot (1024 x 2 = 2048MB = 2GB of memory). You could then sell the two 512MB modules on an auction site such as eBay.
There are some other issues that you should know about, such as running DDR, DDR2, and DDR3 RAM in single-channel and dual-channel modes, so read the information in this article to make sure that you buy the correct memory for your computer's motherboard or brand-name PC.
Note that Intel's new Socket LGA1366 Core i7 quad-core processors now have a memory controller onboard for the first time that can run DDR3 memory in triple-channel mode, so the motherboards that run them have six DIMM memory slots in order to run two sets of three modules in triple-channel mode. They can also run DDR3 memory in single-chanel and dual-channel modes. AMD's processors have had an onboard memory controller for many years.
Intel's Core i7 quad-core processors can only use DDR3 memory. AMD's Phenom II quad-core and triple-core processors can be installed in both Socket AM2+ and Socket AM3 motherboards. They run on DDR3 memory when installed in a Socket AM3 motherboard and run on DDR2 memory when installed in a Socket AM2+ motherboard.
RAM memory modules: The warranty periodThe warranty period for generic (unbranded) RAM memory modules is the usual twelve months. However, a brand-name manufacturer such as Crucial provides a lifetime warranty. That means that the memory is covered by the warranty as long as it is used by the purchaser in a computer that supports it. That amounts to about five years, because new types of RAM is always being released, and the older modules won't be supported by new motherboards. See the Warranties page on this site for more information on them in regard to computers or their components. Individual components, such as the monitor, can have a longer warranty period than the computer itself. Measures you should take before taking your comuputer in for repairsNote that if you are sending a computer in for repairs, it's an excellent idea to make a note of the details (make, model, etc.) of all of the components, including the RAM, that is installed. It is a simple matter for a crooked technician to replace high quality components with cheaper ones. You could put a small white dot of Tippex, or other non-removable mark, somewhere on the component so that you can check that it is still there when the system is returned. Taking close-up photographs of the system that have been verified by witnesses might provide proof of theft in a court case. However, the outfit responsible could accuse you of replacing the components yourself in order to receive compensation or better components in exchange for inferior ones, so you might not be able to obtain any redress. But at least you'll know never to deal with the place again. However, if you appeal to the chief executive there, and you look honest, you might have the matter put right. |
Up to a point, increasing the amount of RAM in a system can deliver very noticeable performance gains, but increasing it over that point usually delivers ever decreasing performance gains.
The following article uses a laptop PC to gauge the increase in performance with increased amounts of RAM memory and the performance gains made by using dual-channel mode instead of single-channel mode, but the findings apply to a desktop PC. The second article's title explains its contents.
RAM Performance Guide -
http://laptoplogic.com/resources/detail.php?id=61
How much RAM is enough? -
http://www.hardwareinsight.com/how-much-ram-is-enough/
That said, performance gains are not the only benefit of increasing the amount of RAM in a computer, because, assuming there is sufficient hard disk drive space, the more RAM a system has, the bigger the programs it can run, and the more programs it can have loaded to run at the same time.
Note, however, that Windows 95, 98, and Me (Windows 9x) have limited System Resources that limit the number of programs that those versions of Windows can run at the same time. Windows keeps track of them via two 64KB blocks of memory (128KB) within the 640KB of Conventional RAM memory used by DOS.
Windows XP, Windows 2000, Windows Vista and Windows 7 don't have problems with what are known as System Resources, but the Windows 9x versions of Windows can crash or require that the system is restarted if they reach too low a level.
A four-part series on System Resources in Windows 9x - what they are, why they are unrelated to the amount of RAM, how to manage them and prevent memory leaks, etc. - is available here:
http://content.techweb.com/winmag/columns/explorer/2000/14.htm
What is RAM memory and what does it do?
| RAM PROBLEMS AND SOLUTIONS Click here! to visit the page on this site devoted to RAM problems and their solutions. |
RAM memory stores the data in electronic memory cells that are arranged in grids in much the same way as cells are arranged in a spreadsheet, from which data, in the binary form of ones and zeros, can be accessed and transferred at random to the processor for processing by the system's software - or transferred directly to the hardware components that can use Direct memory Access (DMA), including disk-drive controllers, graphics cards, network cards and sound cards.
The RAM is conventionally controlled by the memory controller of the motherboard's chipset, or, as is now also the case with AMD Athlon 64 processors and Phenom processors and Intel Core i7 processors, by a memory controller built into the processor itself, which is capable of running the memory it supports in single-channel mode and in the faster dual-channel mode (plus triple-channel mode for the Intel Core i7 processors). More information on DDR, DDR2 and DDR3 memory is provided further on in this article.
If the memory controller is built into the processor, the motherboard that runs the processor won't have a memory controller in its chipset.
The memory controller on a motherboard resides in a chip called the north bridge.
If the motherboard supports dual-channel mode (or triple-channel mode), and it also has an integrated graphics engine, the system performance will be boosted because integrated video uses system RAM, and RAM running in dual-channel or triple-channel mode is 5% to 10% faster than memory running in single-channel mode.
Identify the RAM memory in your systemIf you want a quick way to identify a PC's processor, motherboard, and RAM, the free CPU-Z is ideal. It provides plenty of information on those components in Windows 95/98/Me/XP/Vista and Windows 7. Download and install the program and look under its Memory and SPD tabs. If you are online, you can use The Crucial System Scanner to identify the make/model of the PC's motherboard, how much memory is installed, and in which slots. CPU-Z identifies the make of the memory installed; Crucial's scanner does not. It is best to install a memory upgrade made by the same manufacturer as the existing memory. Recent articles on RAM memoryLGA 1156 Memory Performance: What Speed DDR3 Should You Buy? : Which Memory Speed Do You Want? - "We’ve seen how faster memory scales on Phenom II, Core 2, and Core i7 for LGA 1366. Now it’s time to analyze the impact of different memory speeds on a Core i7-870-based LGA 1156 platform. We test from DDR3-800 to -1600 at tight and loose latencies." - http://www.tomshardware.co.uk/core-i7-870-1156,review-31748.html Value DDR3 For Intel's P55: Six 4GB Kits Rounded Up - "The exceptional value of LGA 1156-based platforms demands memory modules equal in value. Testing Newegg’s six cheapest 4GB dual-channel kits revealed some surprisingly good parts. We're comparing them today, with a definitive winner you'll want to see." - http://www.tomshardware.co.uk/newsletters/15/2009-11-12.html DDR3 On A Budget: Six 6 GB Memory Kits : Finally, 6 GB Gets Affordable - Triple-channel 6GB kits finally dropped below $100 last month. Today’s overclocking and under-latency tests prove how much value these low-cost parts can provide. Sure, Intel's Core i5 might be close at hand, but don't think Core i7 is going anywhere." - http://www.tomshardware.co.uk/6gb-ddr3-x58,review-31649.html Scaling Summary: DDR3 Memory On Core 2, Core i7, And Phenom II - "Today we're looking at the impact of fast DDR3 RAM versus slower RAM speeds in Core 2 Quad-, Core i7-, and Phenom II X4-based platforms. Now it’s time to summarize: which architecture best utilizes the benefits of multi-channel DDR3 memory configurations?" - http://www.tomshardware.com/picturestory/511-memory-scaling-ddr3.html DDR3 Memory Scaling: Intel's Core 2 Quad Examined : DDR3 On Core 2 Quad: Which Speed And Timings Are Best? - " This is our third RAM scaling story in a series that will conclude next week. In this piece, we're comparing a number of different DDR3 memory speeds using both tight and relaxed timings. Which memory setting is best for your Core 2 Quad setup?" - http://www.tomshardware.co.uk/core-memory-scaling,review-31616.html DDR3 Memory Scaling On AMD's Phenom II X4 : Which RAM Speed Is Best? - "DDR3 memory is available in speeds ranging from DDR3-800 to DDR3-2133. Which is the best memory choice for AMD’s Phenom II X4?" - http://www.tomshardware.co.uk/phenom-ii-ddr3,review-31596.html Do You Really Need More Than 6 GB Of RAM? : Is “Too Much” Really Just Enough? - http://www.tomshardware.co.uk/memory-module-upgrade,review-31549.html How Much RAM Do You Really Need? : The Need To Invest In 2 GB Of RAM Is Not Marketing Hype - http://www.tomshardware.com/reviews/ram,1190.html Dreaming of a PC with 192GB of RAM? Dell makes it reality - "Dell Inc. announced on Tuesday a new PC that, among its other impressive specs, can be upgraded to sport as much as 192GB of ultrafast DDR3 RAM. The Precision T7500 sports 12 memory slots, each of which can take a PC10600 stick (1333 MHz) of up to 16GB..." - http://www.computerworld.com/action/article.do?... Triple-Channel DDR3: 6GB Kit Roundup : Have Memory Manufacturers Dropped The Ball? - "DDR3 deskto memory has been around for nearly two years, but it wasn’t until a few months ago that we finally got to see the first platform specifically designed to take advantage of its increased data rate. With an on-die memory controller that supports triple-channel mode, Core i7 processors have produced the biggest memory bandwidth improvement we’ve seen since RDRAM met Netburst. But once again, a transition that should have been smooth has been met by memory manufacturers who had other ideas." http://www.tomshardware.co.uk/triple-channel-ddr3-i7,review-31494.html 4GB Gets Cheap: 9 Dual-Channel Kits Compared - http://www.tomshardware.co.uk/ddr2-ram-memory,review-31446.html Going For 4GB: DDR2-1066 Kit Round-Up : 4 GB DDR2 Kits For the Masses - http://www.tomshardware.co.uk/4gb-memory-overclocking,review-31337.html Pushing the Limits of Windows: Physical Memory - http://blogs.technet.com/markrussinovich/archive/2008/07/21/3092070.aspx Mainstream-Ready? DDR3-1600 Shootout : Mainstream ready? - Vendors and readers alike have been asking for a DDR3-1600 (PC3-12800) shootout ever since our DDR3-1333 Comparison, but we waited for these parts to reach mainstream prices before obliging. By the time 2 GB kits finally reached out price point, the reality of living with Windows Vista and its huge memory demands had finally set in." - http://www.tomshardware.co.uk/DDR3-1600-PC3-12800-Memory,review-31320.html Tom's Ultimate RAM [DDR2/DDR3] Speed Tests - "Our conclusion is very simple: you get the best bang for the buck if you stick to the mainstream of the memory market, which currently is still DDR2-800 or 1066, preferably at low latencies. DDR3-1066 and -1333 memory do not yet result in better performance... It’s worth noting that DDR2 memory is amazingly affo dable at its current pricing point. 4 GB kits look especially appealing, but remember that you’ll need a 64-bit operating system to take advantage of all of it." - http://www.tomshardware.co.uk/toms-ultimate-ram-speed-tests,review-30648.html Vista Workshop – Performance Boost with 8GB of RAM - In order to be able to utilize the entire system memory, you will therefore need to use a 64 bit version of Windows Vista. In this article, we will take a look at memory usage under the 32 and 64 bit versions of Windows Vista and analyze how the operating system behaves with different amounts of RAM." - http://www.tomshardware.co.uk/Microsoft-Windows-Vista,review-30272.html DDR3-1333 Speed and Latency Shootout - "Today, we bring you what should have eventually become the "mainstream choice" of DDR3 speeds, as its 1333-MHz data rate falls between the "low-cost" and "high-performance" 1066 MHz and 1600 MHz standards that fill the spectrum. A total of 13 top brands were invited to participate, and eight were able to respond with a total of ten kits for your consideration." - http://www.tomshardware.co.uk/ddr3-1333-shootout,review-29939.html X38 Comparison Part 2: DDR3 Motherboards - "We covered the technology in our X38 Express technical introduction, and examined its major features again in our DDR2 motherboard comparison. Now we’re ready to see what benefits DDR3 will bring..." - http://www.tomshardware.co.uk/x38-comparison-part2,review-29775.html Parallel Processing, Part 2: RAM and HDD - "As expected, the performance difference between single channel and dual channel DDR2-800 memory using an up-to-date Core 2 Duo system is little to nil, depending on the benchmark - most tests show differences, but they are really small. For games and enthusiast PCs, we recommend sticking to high-performance dual channel RAM, because the memory is one of those components that you want to perform best for a smooth experience. For regular applications, though, it doesn’t really matter much whether you run single or dual channel. Two 1 GB DIMMs typically are cheaper than a single 2 GB module, but a single DIMM will reduce your power consumption by several watts (which might just be more interesting than it is important)..." - http://www.tomshardware.co.uk/parallel-processing-RAM,review-29694.html Tight Timings vs High Clock Frequencies - http://www.tomshardware.co.uk/...review-1633.html Virtual memory (the Windows swap/paging file) is not RAM memoryVirtual memory is a reserved area of a hard disk drive used as a buffer or cache that serves the RAM memory. It is also known as a paging or swap file. If you want information on it in Windows XP's Help and Support, enter the words paging file in the Search box, because using the words virtual memory turns up nothing. The files used most frequently by running programs are stored in the RAM so that they can be accessed as quickly as possible. Files used less frequently by running programs are placed in the swap file. They're moved into RAM when required. Since accessing RAM memory is much faster than accessing the fastest of hard disk drives, the more the system has to use virtual memory, the slower it operates. All of the versions of Windows make use of virtual memory, but the more RAM the system has at its disposal, the less it needs to make use of virtual memory, and vice versa. In Windows 95, 98, and Me the virtual memory settings are accessed by clicking on My Computer with the right mouse button, followed by clicking Properties in the menu that presents itself. Click on the Performance tab in the window that comes up, and then click the Virtual Memory button. The procedure for Windows XP and Windows 2000 is the same for the first two steps, but then open the Advanced tab. The Performance Options window opens. Click on its Advanced tab. To change the settings, click on the Change button under Virtual memory. Read Managing Processes and Tasks in Windows Vista to find out what the differences are between the Task Manager in Windows XP and Windows Vista. Windows Vista: SuperFetch and External Memory Devices - "Windows Vista sports a new memory performance enhancement system called SuperFetch and a new way to extend the virtual memory by way of External Memory Devices (EMD)." - http://articles.techrepublic.com.com/5100-10877_11-6039379.html?tag=nl.e132 How To Move the Paging File in Windows XP - This article describes how to change the location of the paging file in Windows XP. The paging file is the area on the hard disk that Windows uses as if it were random access memory (RAM) This is sometimes known as "virtual memory." By default, Windows stores this file on the same partition as the Windows system files. You can increase the performance of Windows, and increase free space on the boot partition, by moving this file to a different partition. - http://support.microsoft.com/?kbid=307886 Note that you shouldn't change the settings unless you know what you're doing. Windows 95/98/Me manages the virtual memory itself by default. Windows XP also manages the virtual memory itself by default, but it makes the size of the swap file 1.5 times the amount of available system RAM. If the system RAM is shared by a video chip on the motherboard, the amount of RAM available to the system (minus the RAM used by the video chip) is used in the calculation. Windows: RAM and virtual memory management informationWindows 98 and Windows Me Memory Management - http://aumha.org/a/memmgmt.htm Windows 98 and Windows Me information on the conservativeswapfile setting [in the system.ini file] and other memory tweaks: http://aumha.org/win4/a/memmgmt.htm. You can try the "conservativeswapfile" setting on any Windows system that has 128MB or more of RAM, but it has no effect in Windows XP and Windows 2000. For information on memory settings that work in those versions of Windows, go to http://aumha.org/win5/a/xpvm.htm. The system resources of Windows 95, 98, 98 SE, and MeIf a computer produces an error message that informs of a lack of system resources, this is not is not referring to a lack of RAM. System resources are a limiting factor in DOS-based Windows 95, 98, and Me. Two small 64KB blocks of the RAM used by DOS called Convention Memory are used to contain operating information about the programs and processes that are running. As this 128KB of reserved RAM memory comes close to being used up, those versions of Windows become unstable. To regain stability requires closing programs down or rebooting the computer. Because Windows 2000 and Windows XP don't make use this memory, the lack of system resources is not an issue with them. System Resources FAQ - http://www.aumha.org/a/resource.htm System Resource Issues - http://content.techweb.com/winmag/columns/explorer/2000/14.htm |
Asynchronous and Synchronous DRAM
Whether RAM is asynchronous or synchronous is a technical specification that doesn't have to be known in order to make a correct purchase decision, because other specifications are used to determine the type and flavour of RAM. For more information on this subject, visit this page:
http://www.pcguide.com/ref/ram/timingAsynch-c.html
EDO, SDRAM, DDR SDRAM and Rambus RAM
Until motherboards with chipsets able to use DDR RAM became available, Intel's Pentium 4 processors could only use Rambus RDRAM, which runs at effective speeds of 400MHz and 800MHz (the 800MHz kind is dual-channel RDRAM) and which is comparatively very expensive compared to standard PC 100 and PC 133 SDRAM, and PC 1600, PC 2100, PC 2700 and PC 3200 DDR RAM.
But motherboards with the required chipsets soon became available that allowed Pentium 4 processors to use DDR RAM - and the latest development of that time called dual-channel DDR RAM, which the processors made by AMD (but not those made by Intel) were able to employ, because AMD's processors had the required inbuilt memory controller instead of a memory controller on the motherboard. Intel's Core i7 quad-core processors are the company's first to use an inbuilt memory controller, which can run memory in dual-channel and triple-channel modes. Both of those modes were discussed further back in this article.
The table below shows the history of the types of RAM from 1987 to 2002. The PC66 to PC133 in the three lighter blue rows refers to SDRAM (Synchronous Single Data Rate) memory, the forerunner of DDR SDRAM.
Rambus RAM is shown in the two yellow rows, and DDR RAM is shown in the three dark blue rows. You can read about that type of memory here: http://en.wikipedia.org/wiki/Rambus.
FPM and EDO RAM is no longer used in motherboards, but it was used for nearly a decade, and was usually supplied in the form of SIMM modules (Single In-Line Memory Modules). Towards the end of its life, EDO RAM could be purchased in the same DIMM module (Dual In-Line memory Module) form as DDR RAM. 
FSB (the Front Side Bus) and DDR SDRAM
Ordinary SDRAM (the forerunner of DDR SDRAM) comes in types that run at official speeds of 66, 100, and 133MHz, i.e., usually at the same speed as the maximum official Front Side Bus (FSB) speed of the motherboards it runs on. It has been superseded by DDR, DDR2 and DDR3 SDRAM .
Setting unofficial FSB speeds is called overclocking the processor and the RAM.
The FSB is the network of interconnections between the various parts of the motherboard, so the FSB speed is the speed/frequency that the motherboard allows the FSB to run at.
On older motherboards the FSB speed is set by jumpers on the motherboard itself, but all PC motherboards now set its frequency/speed in the BIOS setup program. The higher the number of FSB settings (exceeding the official FSB) that the jumper settings or BIOS provides, the more overclockable the motherboard is.
Front Side Bus - http://en.wikipedia.org/wiki/Front-side_bus
DDR SDRAM (DDR, DDR2, DDR3 memory) uses a new technique to transfer data that effectively doubles its speed compared to SDRAM memory. You can read about the technology involved here: http://en.wikipedia.org/wiki/DDR_SDRAM. It achieves this by transferring data on the both the rising and falling cycles of the clock signal, instead of just transferring data once per clock signal, without increasing the clock speed/frequency.
Dual-channel DDR RAM is a misleading name for recent development that allows the motherboard to run ordinary DDR RAM at an effective speed of double its maximum running speed per module in dual-channel mode. Even though dual-channel kits of two identical modules are on sale, special dual-channel modules are not used. Two ordinary DDR, DDR2 or DDR3 memory modules with the same specification and memory capacity have to be fitted so that they can be accessed together (with the triple-channel mode used by Intel's Core i7 quad-core processors, three identical memory modules have to be used).
Dual-channel architecture -
http://en.wikipedia.org/wiki/Dual-channel_architecture
Triple-channel architecture -
http://en.wikipedia.org/wiki/Triple-channel_architecture
As usual, only motherboard's with specialised chipsets can make, for example, DDR400 RAM runs at an effective speed of 800MHz, or DDR333 run at an effective speed of 666MHz.
However, the reports with regard to the performance increase of dual-channel configurations vary hugely. Some tests indicate that there are significant performance gains; others indicate next-to-no gain. Most of the comments I've found on the web about the benefits of having DDR and DDR2 RAM running in dual-channel mode say that it does not increase the performance of a system much over the performance obtained when using single-channel mode. The reports with regard to the performance of running DDR3 memory in triple-channel mode had yet to appear on the web at the time of writing (June 2009).
PC 100 DDR RAM was named PC 1600 DDR RAM because of its data bandwidth (transfer capacity) of 1.6GB per second. A motherboard must specifically support it. Another term used for it is DDR200 because it runs at effectively twice the speed of the 100MHz FSB that it should run on.
Running DDR200 RAM on a 133MHz FSB would be overclocking it to run at an effective speed/frequency of 266MHz, which may or may not work, because some makes of RAM modules can be overclocked and others refuse to work if overclocked. In any case, you should not overclock any of the devices (processor, video card, RAM) in a computer by increasing the FSB speed unless you have researched the possibilities of doing so first on overclocking websites of which there are many. To find them, just enter overclocking in the Google search box at the top of this page (with its Web radio button enabled).
PC 2100 DDR RAM is just the DDR version of ordinary PC 133 SDRAM. It was named PC 2100 because it has a data bandwidth of 2.1GB per second. Motherboards that support it use an FSB set at 133MHz, which then produces an effective 266MHz bus speed between the processor and the RAM memory.
PC 2700 and PC 3200 DDR RAM is also known as DDR333 and DDR400 respectively.
See the table below for a list of DDR RAM that shows the names for it, the system FSB speeds that it runs on, and its effective maximum running speed/frequency.
The PC Name is derived from the RAM's bandwidth, which is the amount of data in megabytes per second (MB/s) that it can transfer per clock cycle.
For example, data is transferred in blocks of eight bytes. DDR400 RAM has an effective clock speed/frequency of 400 million clock cycles per second (400MHz), so if only one byte of data is being transferred per clock cycle, the bandwidth is 400 MB/s, but since blocks of eight bytes of data are transferred per clock cycle, the bandwidth is 400X8, which is 3200MB/s. Hence its PC Name of PC3200.
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Another way to derive an idea of the speed of RAM is to use the module's cycle time, which is the amount of time needed to complete one clock cycle. A cycle time of ten nanoseconds (10ns) means that 100 million cycles are possible per second, because the chips run at up to 100MHz, which is another way of saying that the frequency is 100 million cycles per second. To reach 133MHz, you need an access time of 7.5ns; for 166MHz, 6.0ns, etc. - See the table below. 1ns = a billionth of a second, or 10 to the power of minus 9, where a billion = 1,000 million, so a billion divided by the 10ns cycle time for PC100 SDRAM comes to 100 million cycles per second.
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However, there are many other factors that affect or determine how fast RAM is. For example, the famous CAS latency, or CL.
The BIOS: Serial Presence Detect (SPD)If your computer has low-latency memory modules, to make sure that they've been detected correctly, enter the BIOS setup program. The RAM settings are usually on a page in the BIOS called something like Chipset Features Setup. If there is an option called SPD (Serial Presence Detect), enabling it makes the BIOS set the optimal timings automatically. SPD refers to a small chip on each memory module that holds the latency settings information. Note that the BIOS doesn't always read the information properly. If you suspect that to be the case, you can set each of the values manually in the BIOS. The lowest presented settings are the fastest. |
Using the fastest RAM modules is only necessary if the computer works as hard as it does while, say, encoding video. For less intensive general-purpose computing applications, slower RAM is good enough.
Computers used mainly for playing the latest graphics-intensive games as well as possible use the latest ATI Radeon and nVidia GeForce video/graphics cards, which have a graphics processing unit (GPU) and currently have up to 2GB of DDR RAM onboard, so the speed of the system RAM is not of much importance.
DDR2 SDRAM and the motherboards that support it
JEDEC is the body responsible for standardising RAM, and it has had the specifications for DDR2 RAM approved since September 12, 2003.
Motherboards that support DDR2 RAM and Intel and AMD processors have been available for some time.
DDR2 SDRAM - http://en.wikipedia.org/wiki/DDR2_SDRAM
DDR3 RAM and the AMD-based and Intel-based motherboards that support it have recently become available.
DDR3 vs. DDR2 - http://www.anandtech.com/memory/showdoc.aspx?i=2989
The next item on this page deals with DDR3 memory.
Below is a table showing the bandwidth of DDR2-400 to DDR2-1066, plus the FSB and effective FSB speeds of the motherboards that support it.
| | | Double Data Rate (DDR) I/O Bus clock | | | |
| DDR2-400 | | | | | |
| DDR2-533 | | | | | |
| DDR2-667 | | | | | |
| DDR2-800 | | | | | |
| DDR2-1066 | | | | | |
Note the correlation between the PC Name and the single-channel mode's bandwidth in megabytes per second - MB/s. The dual-channel mode's bandwidth is double the single-channel mode's bandwidth.
The PC Name of a module of DDR RAM is derived from its bandwidth in MB/s.
It's easy to derive the PC Name from the DDR Type. Data is transferred in blocks consisting of eight bytes each, therefore multiplying the effective speed of the RAM by eight gives its bandwidth.
For example, DDR333 has an effective speed of 333MHz, which is the equivalent of 333 million cycles per second. The bandwidth is the amount of data that can be transferred per second. This RAM transfers eight bytes of data per clock cycle, so multiplying it by eight gives it a bandwidth of 2664 megabytes per second (MB/s).
In other words, the bandwidth is 2664 MB/s because an effective frequency of 333MHz would have a bandwidth of 333MB/s if only one byte of data was transferred per clock cycle, but eight bytes of data are transferred clock cycle, so the real bandwidth is 2664MB/s.
This is rounded up to 2700 to give it the PC Name of PC2700. In the same way, DDR400 becomes 400X8 = 3200, which becomes PC3200.
BIOS settings for DDR2 RAM
The BIOS setup program for a particular motherboard provides settings for the memory that can be modified/overclocked or enabled/disabled.
The user manual that comes with a brand-name PC or motherboard should have a BIOS section that provides information on the settings that are available. If you don't have such a manual, you should be able to download a copy in the PDF format from the PC or motherboard manufacturer's site for a particular make/model of PC/motherboard.
For example, the Asus P5WD2-E Premium Edition motherboard has a chipset that is supposed to support a maximum of DDR2-667 memory, but its BIOS has the settings that allow DDR2-800 and DDR2-1066 memory to be used.
The FSB setting can often be changed in the BIOS. When it is set at 200MHz in the BIOS of the above-mentioned motherboard, the settings in the image shown below become available (DDR2-400MHz to DDR2-800MHz).
However, when the FSB is set to 266MHz, the settings in the image below become available (DDR2-400MHz to DDR2-1067MHz).
Note that the BIOS settings are not standardised for all motherboards. It is up to the motherboard manufacturers which settings they choose to make available for a particular model of motherboard. For example, if a motherboard manufacturer wants to restrict the ability to overclock the processor and memory, the BIOS settings that allow the overclocking of those components will not be made available. This is a good idea from a support point of view, because people with no knowledge about overclocking often jump in at the deep end and ruin components, which are then sent back to vendors as being dead on arrival.
DDR3 SDRAM and the motherboards that support it
Motherboards that run the latest AMD and Intel quad-core processors and the new DDR3 RAM memory that they support are now available.
June 5, 2007 - Pipe Dreams: Six P35-DDR3 Motherboards Compared -
"Intel's P35 Express chipset represents next-generation processor and memory compatibility. While other media outlets consider the 'DDR2 v DDR3' debate, we instead analyze six motherboards that support the newest memory 'standard'..." -
http://www.tomshardware.co.uk/...review-2321.html
DDR3 memory components can transfer data twice as fast as the highest speed DDR2 memory components. The major advantage of DDR3 memory is the ability to transfer data at twice the rate of DDR2 memory. Moreover, the DDR3 standard allows for chip capacities of 512 megabits to 8 gigabits, allowing for a maximum memory module size of 16 gigabytes (16GB).The table below shows both the DDR3 and PC names for different module speeds (e.g., DDR3-800/PC3-6400), and their main specifications.
| | | Double Data Rate (DDR) I/O Bus clock | | | |
DDR3-800 | | | | | |
DDR3-1066 | | | | | |
DDR3-1333 | | | | | |
DDR3-1600 | | | | | |
DDR3-1866 | | | | | |
DDR3-2000 | | | | |
ARTICLES ON DDR3 MEMORY
DDR3 SDRAM - http://en.wikipedia.org/wiki/DDR3_SDRAM
DDR3 vs. DDR2 - http://www.anandtech.com/memory/showdoc.aspx?i=2989
What is DDR3 Memory? -
http://www.simmtester.com/page/news/showpubnews.asp?num=145
Registered and ECC RAM
ECC stands for Error Correcting Code. It is error correction hard-coded into the RAM chips themselves. ECC RAM - also known as parity RAM - is more expensive than other types, and is mainly used in mission-critical systems such as network servers that work around the clock.
Registered or buffered RAM has a built-in buffer that stores the data before it is transferred to the hardware memory controller. It increases the reliability of the RAM enormously. Even so, most of the RAM used in personal computers is unbuffered, and works reliably enough in that role.
DDR RAM modules that are both registered and have ECC are available, and modules that are registered without ECC, or are unbuffered (not registered) but have ECC are also available.
You can only install registered and/or ECC RAM in a system if it is supported by the motherboard. For current systems, this will be DDR RAM that is registered and/or incorporates ECC.
So, ECC detects and corrects memory errors, and registered means that the RAM registers memory information for one clock cycle to ensure that all communications with the memory controller (part of the motherboard's chipset, or built into the processor itself) can be more effectively checked and controlled.
Registered and ECC memory technology is designed to provide the greatest possible stability and reliability. Unfortunately, it slows down the RAM's data bandwidth. Moreover, because it requires a more involved manufacturing process, it is more expensive than non-ECC and unregistered RAM. Speed and price are the main reasons why you're unlikely to find this type of memory in the average home computer, but it is often found in high-end mission-critical workstations and servers.
Can you mix and match ECC and non-parity modules?
No! When adding additional memory, you need to match the RAM that is already in the system. To determine if the system has parity (ECC) RAM simply count the number of black memory chips on each module. Parity and ECC memory modules have a chip-count divisible by three or five. Any chip-count not divisible by three or five indicates that it is non-parity RAM module.
Still confused about the different types of RAM?
It is very easy to become confused with the different types of RAM that will or will not run on the different types of motherboards that support Intel or AMD processors.
Start by remembering that motherboards that support Intel processors never support AMD processors, and you are half way towards clearing up the confusion.
The motherboard must support a given processor if you are to use it. It is then just a simple matter of consulting the motherboard's manual to find out the types of RAM and the processors that it supports.
If you don't want to do that and you know the make and model of your brand-name computer, or the make and model of the computer's motherboard, you can find out which RAM it supports by using the UK or US Crucial Memory Selector provided at the top of this page, where you can also find a link to free software that can identify your computer's motherboard and memory.
Otherwise, if you don't already possess a manual for your computer's motherboard, you can download a copy from its manufacturer's website. As long as you only install items on a motherboard that are certified by its manual to run on or with it, you can't go very far wrong.
Most systems that have motherboards that use superseded SIMM memory modules require you to use matching pairs of modules to fill a bank of slots on your motherboard. If you fail to match them correctly, the system won't even boot.
For example, if you want to install 64MB of EDO RAM that comes in the outdated SIMMmodule form, you may have to install two matching 32MB modules instead of going with just one 64MB module, or one 32MB module plus two 16MB modules. Therefore, always check your system and motherboard manuals before you place an order.
Note that only dual-channel DDR RAM modules have to be installed in matching pairs. You do not need to install DIMM (SDRAM or DDR RAM) modules in pairs. Modern motherboards are also often much more forgiving about which DIMM modules can be fitted - they do not all have to be of the same capacity. - A 64MB module can be installed with 128MB and 256MB modules, etc.
With the triple-channel mode used by Intel Core i7 processors running on Socket 1366 motherboards, the modules have to be installed in matching sets of three to run in that mode. If matching pairs of modules (of the same type and capacity) are installed, the memory runs in dual-channel mode.
Remember, never skimp on quality when it comes to RAM.
Even when buying a new PC always obtain a system specification and check which make of RAM is installed.
Only grade-A memory will do, and it is only manufactured by the major manufacturers of RAM.
RAM is probably the most critical system component. Every bit of data passes through it to get to the processor, so it has to be 100% functional 100% of the time if data corruption is not to take place.
It is a fact that many program crashes can be attributed to cheap, error-prone or defective RAM. Therefore, if the system has generic, low-cost RAM, insist that grade A RAM from one of the major manufacturers is installed.
The major manufacturers of RAM are Crucial Technology (also known as Micron Technology), Rambus, PNY (uses Siemens chips), Kingston, Corsair, LG, Hyundai, Mushkin, and Samsung.
If the vendor's advertisement, or system specification doesn't name the manufacturer, then it is usually generic RAM that is on offer, much of which is not likely to be grade A RAM.
If the manufacturer of the RAM isn't one of those named above, it might still be a respectable make, so to find out information and read reviews on it, you can enter its name in the Google search box provided at the top of this page (with its Web radio button enabled).
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