Depending on its architecture, there will always be at least one notch in a RAM module, but never more than two. The SDRAM module below has two notches, but a DDR DIMM module (below that) will only have one, and a RIMM module (used only in motherboards designed for Pentium 4 processors) has two closely-spaced notches.

Note that you should consult the motherboard's manual to find out if the slots have to be filled in an order of rank. Some motherboards require that Bank 0 be filled first, followed by Bank 1 and 2, etc., while some motherboards allow any bank to be filled.

Systems using certain BIOS versions and 768MB or more of RAM suffer a marked slow-down

Certain versions of the Award (now owned by Pheonix) BIOS installed by many motherboard manufacturers slow down the computers that use them very markedly when more than 768MB of RAM is installed. This problem affects BIOS versions prior to number 1004, so, if you have not done so, and you have or want to install 768MB or more of RAM, download and install the latest BIOS, currently at number 1011, from the PC/motherboard manufacturer's site.

Too much RAM can cause problems with some versions of Windows

Note that if you are upgrading your RAM memory, a computer using Windows 95 or Windows 98 (first edition) will not recognise more than 256MB. Moreover RAM that Windows cannot cache (recognise) will be accessed as slowly as the virtual memory swap file (win386.swp) that Windows creates on the boot hard disk drive to use when the amount of RAM runs out. Therefore, adding too much RAM can slow down a system considerably. Unless you are using a non_Windows operating system such as Linux, and unless you employ the fix a link to which is provided below, your must have Windows 98SE or run a later version to use more than 256MB of RAM.

This limitation does not apply to Windows 2000 and Windows XP.

Moreover, it has now become known the Windows 98 SE (second edition) has trouble with 512MB of RAM and more. Windows 9.x systems were not designed to use large amounts or RAM. Most home users of Windows 9.x are unlikely to require this much RAM in any case, so, if possible, it is advisable to install less than 512MB. If you need to use more, use Windows 2000, or Windows XP, both of which are based on the Windows NT architecture. Windows 95, 98, and Me are based on Windows 95 architecture.

If you have more than 512MB of RAM installed and this causes any problems, you can restrict the amount of RAM used to 512MB (or any other amount) by entering msconfig in the Start => Run box, clicking the Advanced button, and enter the appropriate restriction in the Limit memory to... box - and enable it with a check mark.

There is a configuration file fix that can be applied to make Windows 98 function with as much RAM as you are likely to throw at it. See this excellent article - Windows 98 & WinME Memory Management -

http://aumha.org/a/memmgmt.htm

You can also read more about this in a Knowledge Base (KB) article Q253912 at Microsoft's site -

http://support.microsoft.com/support/kb/articles/Q253/9/12.asp

Microsoft has a tendency to change the links to KB articles, so if a link fails to work enter the article's Q number in the search box on the following page. As you can determine from the information in the link itself, the Microsoft link above leads to the article with the Q number of Q253912.

http://support.microsoft.com/default.aspx?pr=kbinfo&

Memory-card readers

If you use several different kinds of devices that use their own kinds of memory cards, you can purchase memory-card readers that can read the different cards.

For instance, an MP3 player uses MMC cards, a Personal Digital Assistant (PDA) uses Compact Flash cards, and a Sony Vaio notebook computer uses it own Memory Stick cards.

You could spend a long time transferring files from the devices to a desktop computer by using, say, USB cables. But if you buy an inexpensive memory-card reader, you can eliminate the need to plug and unplug lots of different USB cables.

The 6-in-1 Media Reader requires a 3.5" drive bay of the kind that houses a floppy disk drive. It reads Multimedia Cards (MMC), Secure Digital (SD), Memory Stick, PC Card (PCMCIA), Compact Flash, and SmartMedia card formats. You can copy the contents of one type of card to the desktop computer's hard drive, insert a different card, and copy the contents to it, or you can just copy the contents to the hard drive.

You can buy the 6-in-1 Media Reader from http://www.simply.co.uk/.

The USB 2.0 6-in-1 Flash Reader, is an external USB device that can be connected to either a notebook or desktop computer. It also has a USB 1.1 port that enables you to connect a printer or scanner to it.

You can buy a 6-in-1 Flash Reader from http://www.watford.co.uk/.

Motherboard and BIOS settings

The motherboard's manual will also provide you with any jumper settings that might be used to set the RAM's speed - for 66MHz EDO RAM, PC 100 SDRAM at 100MHz, PC 133 SDRAM at 133MHz, etc. - and the BIOS settings that might set the speed instead of motherboard jumpers, as well as set other optional settings such as the bank interleave and timing settings.

For images of and information on the jumpers and DIP switches used on motherboards to enable various functions, visit the Motherboard page of this site.

You can also visit this page of the PC Guide - http://www.pcguide.com/ref/mbsys/cache/char_Cacheability.htm to read an article on RAM cacheability. There are also several other pages devoted to RAM on this site.

Visit this site for a guide called How to Install Memory in Your PC.

And visit http://www.geocities.com/budallen98_98/dennis.html and search for the article called How Much RAM Will Windows 98 "USE".

Unfortunately, the ability of Windows to use RAM does not always coincide with ability of a motherboard's chipset to cache RAM, so be sure to check your motherboard's manual before you upgrade. The motherboard's chipset determines how much RAM can be cached. If the motherboard has an elderly chipset, the amount of RAM it can cache might be limited to as little as 64MB.

If a motherboard can only cache 64MB of RAM, such as one with the elderly Intel TX chipset, and you install 128MB, even if it works, it will slow the system down significantly, because the excess RAM cannot be cached, and so will be accessed in the same relatively slow manner as the virtual memory swap file that Windows sets up on the hard disk drive is accessed.

The moral of the story - if you have an ageing PC, always find out how much RAM your motherboard can cache before upgrading.

Only purchase a new computer that has at the very least PC 133 SDRAM. This kind of RAM is certified to run at 133MHz.

If you are looking for a system with the fastest available RAM consider one with DDR RAM, or the more expensive, but not necessarily superior Rambus RAM, which is supplied in modules called RIMMs.

If you are buying RAM as an upgrade, purchase it from a supplier of quality RAM such as Crucial.

RAM of poor quality will isn't worth any savings you can make, because it can be the source of all kinds of system failures.

Motherboards that use EDO RAM supplied as SIMM modules are no longer being made, but you can still purchase EDO RAM from suppliers such as Crucial, or second-hand from computer auction sites.

Make sure that the RAM installed or installable on your motherboard is supplied as one or more DIMM (or, if your motherboard supports it - RIMM) modules.

Unless your motherboard can run the RAM speed and the bus speeds independently of one another (as is the case with the FIC VA-503+ AT form-factor motherboard), remember not to use ordinary 66MHz RAM when the motherboard bus (FSB) is set to run at 100MHz - the newer PC100 (100MHz) SDRAM is required.

Likewise do not use PC 100 SDRAM, which runs at 100MHz, on a 133MHz system bus. Use PC 133 SDRAM.

How to identify the size of RAM modules

Question

You have purchased a large collection of RAM modules - SIMMs and DIMMs - that you want to resell, but you have no idea of how to identify the memory capacity in megabytes (MB) of the individual modules, and you want to know if there is any way to determine the size of a module other than by installing it on a motherboard in a computer that supports that type of RAM.

Answer

It is possible to identify the chips by part number. You have to identify the size of each the chips on a module, and then multiply the size by the number of chips on the module to determine its memory capacity.

Different RAM manufacturers have developed their own methods of identification, so it is has become difficult to identify the chips without looking up the exact part number on a website that provides the information.

Luckily, the Internet has made doing this fairly easy via the Google search engine.

Unless they have been remarked by unscrupulous dealers that are selling substandard modules not passed for use in a computer as computer-quality, all of the chips on a particular module will have the manufacturer's name (or logo), and a part number printed on them.

For example, a 30-pin SIMM module with nine chips on the module, could have the part number - KM41C4000AJ-8. Drop the AJ-8 (the first letter is usually the quality - A, B, C, etc.), then use KM41C4000 to conduct a Google search. You should be provided with links to many sites that provide information about part numbers. One of them is http://www.memoryusa.com/guide.html.

The KM indicates parts made by Samsung. The 41 indicates that it is a 1Mbit x 4 part. This means that the chip holds 4Mbits. Eight of the nine chips hold memory, so this is a 8 x 4Mbit, or 32Mbit module. There are eight bits to a byte, therefore this is an 4MB module. The ninth chip is there to add parity. This was used as a means of checking for memory errors that is no longer used.

For a 168-pin DIMM module that has eight chips (no parity chip), and the part number - TMS626812DGE-12A - you would use TMS626812 to search for information on it.

Each chip is a 2Mbit x 8 (16Mbit) SDRAM chip. There are eight chips, so this is a 16MB SDRAM module, which is slow compared to the fastest speed that SDRAM modules reached. The 12 in the part number indicates that the module has a maximum frequency (speed) of 66MHz. SDRAM modules, now superseded by DDR and Rambus RAM, reached a maximum speed of 133MHz.

Decode RAM chip part numbers

At the following site, you just enter the RAM chip part numbers to find out the manufacturer and specifications. -

http://www.chipmunk.nl/DRAM/ChipManufacturers.htm

Windows 2000

According to received opinion, this is the situation at present.

Windows 2000 needs at least 128MB of RAM to work properly. More RAM comes in handy when multitasking in Windows 2K. The Council on Computing Power has launched a new Windows 2000 info-site, with articles, studies and more...

Windows XP

Windows XP, Microsoft's latest 32-bit series of operating systems for both the home and dedicated server and workstation networking has a recommendation of a minimum system requirement of 128MB of RAM, with 256MB preferred.

Indeed, I have just read a Crucial Technology newsletter that recommends 320MB of RAM to run the standard version of the Office XP suite. A bit of eye-opening information, since high-end PCs costing £2000 usually only come with 256MB.

Are you ready for Windows XP?

October 25 2001 was the Windows XP launch day. Visit the Crucial Guide to Windows XP to find out how much RAM is needed to run it and the XP Office suite.

http://www.crucial.com

Mixing brands can often cause problems

Using cheap no-brand, generic RAM can also be a common a source of system failure, so make sure that you purchase RAM manufactured by one of the major manufacturers such as Crucial, PNY, Kingston, Samsung, Panasonic, Corsair, etc.

Cheap, no-brand RAM can be especially prone to failure if the processor has been overclocked to a faster speed than its designated speed by increasing the system bus, from a default of, say, 100MHz to 112MHz, if the 112MHz setting is supported by the motherboard but probably not by the RAM. The cheap RAM will probably not be able to handle the increase and cause Fatal Exception and Page Fault failures.

The motherboard's newsgroup will also contain postings about troublesome brands, or anomalies, such as having 64MB of RAM working perfectly well and 128MB, as two by 64MB modules, refusing to work.

All of the PC's purchased during the last three years should be able to cache as much RAM as you are likely to install.

Also make sure that it is of the right type (EDO/SDRAM/, buffered/unbuffered, error-checking code (ECC) RAM, etc.), and check the motherboard's website for compatibility issues. The specifications will be listed in the motherboard's manual.

Windows 98 can itself use as much RAM as any current motherboard. However, installing more than 64MB of RAM on a system running the original (FAT 16) version of Windows 95 will slow the system down. Not being able to cache more than that amount of RAM means that it takes its time accessing it. Windows 95 versions OSR 2.0, 2.1, and 2.5 (FAT 32 versions) can all cache the same amount of RAM as Windows 98.

The first Pentium 4 processors run on Socket 423 motherboards, most of which support only Rambus RAM. But the latest incarnation of P4s run on Socket 478 motherboards, some of which support DDR RAM

The more expensive RamBus RAM, the RIMM modules of which have be installed in pairs, require dedicated slots that will not accept SDRAM or DDR RAM DIMM modules.

SDRAM modules do not have to be installed in pairs; single modules will function.

Not only do you have to purchase a dedicated motherboard for a Pentium 4, you also have to purchase a dedicated case to house it. A special power supply unit with extra power lines is required, and the case has to have extra stand-off points to support the motherboard.

For Intel Pentium III and Celeron processors, and AMD Athlon and Duron processors a standard mini, midi, or full tower ATX case is required to house ATX or micro-ATX (M-ATX) motherboards.

Another good reason to buy AMD. You can use a standard ATX case to house the motherboards that support all of its processors.

Ordinary SDRAM comes in types that run at official speeds of 66, 100, and 133MHz, i.e., usually at the same speed as the default Front Sided Bus (FSB) speed of the motherboard.

The FSB is the network of interconnections between the various parts of the motherboard.

DDR SDRAM uses a new technique to transfer data that effectively doubles its speed. This kind of RAM is being used on motherboards that run AMD Socket A Athlon and Duron processors, which are physically identical apart form the amount of onboard Level 2 cache they contain, and the bus speed that they run on - 100MHz for the Duron, and 133MHz for the Athlon.

PC 100 DDR RAM has been named PC 1600 SDRAM because of its data bandwidth (transfer capacity) of 1.6GB per second. A Socket A motherboard must specifically support it. Motherboards with this capability are available from most of the major motherboard manufacturers.

In short, PC 1600 SDRAM is the DDR equivalent of ordinary PC100 SDRAM.

But further confusion is being added with the advent of PC 2100 DDR RAM, which is just the DDR version of PC 133 SDRAM. It was named PC 2100 because it has a data bandwidth of 2.1GB per second. Special Socket A motherboards support it and the new range of Athlon XP processors that use it. These motherboards will have a 133MHz FSB and a 266MHz bus speed between the processor and the RAM memory.

Earlier Athlon processors (Thunderbirds) that use 100MHz FSB are marked with a B, and the new ones using the 133MHz FSB are marked with a C.

The Duron range of processors will keep running on a 100MHz FSB with a 200MHz processor-to-RAM bus speed.

Just remember that you need to buy a motherboard with a chipset that supports PC 2100 DDR SDRAM if you want to run the Thunderbird Athlons that use it, or one of the new Athlon XP processors.

The VIA KT133A is such a chipset. It supports both B and C suffixed AMD Thunderbird processors.

As you will note in the information on Crucial's RAM pricing, provided further down this article, PC2700 and PC3200 DDR RAM (also known as DDR333 and DDR400 respectively) is now available. - See the table below for a list of DDR RAM.

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 an simple matter of consulting the motherboard's manual to find out the types of RAM and the processors that it supports.

You can download the manuals from the websites of most of the major motherboard manufacturers. As long as you only install items on a motherboard certified by its manual to run on or with it, you cannot go very far wrong.

Most systems that have motherboards that use 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, your system will probably not function properly.

For example, if you want to install 64MB of EDO RAM that comes in the outdated SIMM module 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 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 that 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.

Remember, never skimp on quality when it comes to RAM.

Even when buying a new PC always obtain a system specification and check what 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 (http://www.rambus.com/) PNY (uses Siemens chips), Kingston, Corsair, LG, Hyundai, Mushkin, and Samsung.

If the vendor's advertisement, or system specification does not name the manufacturer, then it is usually generic RAM that is on offer, much of which is not likely to be grade A RAM.

Which DDR RAM?

The problem

You want to purchase an ECS K76SA motherboard, and 256MB of PC2100 or PC2700 DDR RAM. You want to run an AMD Duron 1.3GHz processor on the motherboard's front-side bus (FSB) that runs at 200MHz with this processor installed. You know that both PC2100 and PC2700 DDR RAM run faster than 200MHz, so you want to know if the RAM you purchase will be able to run at the slower bus speed used by the processor.

Answer

Even though the processor has a maximum speed (frequency) of 1.3GHz (1300MHz), the effective data transfer rate of the processor is limited to the speed (frequency) of the motherboard's FSB, which in this case, doubled by DDR technology, is only 200MHz. The FSB speed is the speed with which the processor is able to communicate with the rest of the system. It can do its own calculations at 1.3GHz, but, in this case, can only communicate with the rest of the system at 200MHz. This is going to limit the effective speed of the DDR RAM, because the RAM can but won't tranfer data faster than the processor.

The chipsets on AMD Athlon/Duron motherboards allow the RAM bus to run at a different speed from the processor bus.

For example, the base FSB on the above ECS motherboard running a Duron processor is 100MHz, because that is the FSB used by that processor. The processor is able to operate at the DDR (double-data rate), which is 200MHz. (Later Athlon processors use a 133MHz FSB.) If PC133 SDRAM, which runs at 133MHz, is used, the Duron processor has an effective data transfer rate that is 67MHz faster than the RAM, so in this case the slower RAM is creating the bottleneck that is limiting the data transfer speed. But with DDR RAM installed, the processor's effective data transfer speed would be responsible for creating the bottleneck.

Below is a table providing information on the different types of DDR RAM.

If you purchase PC2700 RAM, the Duron 1.3GHz processor runs on a base FSB of 100MHz, doubled to give an effective data transfer speed of 200MHz, while the RAM runs on a base FSB of 166MHz, which is effectively 333MHz using the DDR technology. So, in this case, the processor is creating the bottleneck by having an effective data transfer rate that is 133MHz slower than the RAM.

The motherboard's manual provides the information on the types of RAM that the motherboard can run. You must set the RAM clock speed (in the BIOS, or by setting jumpers on the motherboard) to the speed of the RAM that your purchase. This is 133MHz for PC2100 and 166MHz for PC2700 DDR RAM.

Therefore, if you wanted the RAM speed to match the processor speed, you would install PC1600 DDR RAM. However, you could purchase the highest type of DDR RAM supported by the motherboard. If you decided to upgrade the processor to the highest AMD Athlon processor that it supports, that processor will run on a base FSB of 133MHz, providing an effective data transfer speed of 266MHz. The ECS motherboard supports PC2700 DDR RAM, so if that is installed with the new processor, the effective data transfer rate would be increased from 200MHz to 266MHz, and the bottleneck between the RAM and processor would be reduced from 133Mhz to 66MHz.

The latest AMD XP processors run on a base FSB of 166MHz (DDR 333MHz), so they will transfer data across the system bus at the same speed as PC2700 (DDR 333) RAM. But PC3200 (DDR 400) RAM runs at 400MHz, so the base motherboard FSB would have to run at 200MHz for one of these processors to transfer data across the system bus at the same speed as PC3200 RAM.

RAM websites

The "Ultimate Memory Guide." - http://www.kingston.com/tools/umg/default.asp

If you want to know about the technical details of how RAM works, visit this article. -

How Computer Memory Works - http://www.howstuffworks.com/computer-memory.htm.

And if you want to know how Windows, and other operating systems, make use of a virtual memory swap file on a hard disk drive to expand the system's RAM, read the following article. -

How Virtual Memory Works -

http://www.howstuffworks.com/virtual-memory.htm

"Windows 98 & WinME Memory Management" - http://aumha.org/articles.htm - includes information on RAM and the Windows Virtual Memory swap file.

RAM News

RAM Wars: Return of the JEDEC

JEDEC = Joint Electronic Device Engineering Council

"DDRAM comes into its own right for mainstream and performance PC applications while muscling out SDRAM and Rambus. Here's our analysis of the world of PC memory as it is being shaped by DDR. We also take a look at GDRII and GDRIII."

"This year will bring a radical change in the kind of memory you will buy and how you will buy it. The death knell has begun to sound for SDRAM while DDRAM has become a standard memory device. A bevy of new memory capabilities, such as dual channel DDR, will make life that much more interesting."

http://www.tomshardware.com/mainboard/20030401/index.html

Rambus RAM exceeds 1GHz

Rambus RAM is now available running at a frequency exceeding 1GHz. The new 1006MHz (1.006GHz) Rambus RAM, combined with Intel's 850E chipset and the latest Pentium 4b processor, takes full advantage of the latest 533MHz motherboard front side bus (FSB) frequency. Asus is the first motheboard manufacturer to issue a motherboard - the P4T533 - that supports the new memory.

Micron (Crucial) demo the next generation of memory technology

http://www.simmtester.com/page/news/shownews.asp?num=4597

Reported Memory Does Not Match Installed Memory

RAM information from Microsoft

"When you view the Performance tab in System properties, the amount of memory reported may differ from the actual amount of memory installed in the computer. This behavior can occur for any of the following reasons: Himem.sys is not using all the memory on an EISA computer. A driver or program loading from the Config.sys or Autoexec.bat file is claiming a portion of random access memory (RAM). A virtual device driver loading from the System.ini file is claiming a portion of RAM. A protected-mode driver is causing the memory mismatch. The registry is damaged. A CMOS setting is disabling some of the RAM. You have the 'maxphyspage=' setting in your System.ini file set to restrict Windows from using some of the installed memory. Ramdrive.sys is being loaded in the Config.sys file. You are using a video adapter that is integrated into the motherboard." -

http://support.microsoft.com/default.aspx?scid=kb;EN-US;Q146912