As computer processors have become ever faster the relatively slow speed of RAM is a bottleneck on performance. A slow 66MHz processor can perform an instruction in 15 nanoseconds and it takes 90 nanoseconds to obtain the data from 70-nanosecond RAM. On top of that, a Pentium processor is also trying to perform two operations simultaneously. Because RAM is so slow, modern computers perform all sorts of tricks in an attempt to get data that the processor might need into the higher-speed memory caches.
There are several types of RAM that Pentium computers are capable of using depending on the chipset on your motherboard. I was going to say that before you buy any type of RAM consult your motherboard's manual. But after looking at mine, this may not make things any clearer! The best advice in purchasing RAM is to find a place that will install it for free. They install it, test it, and if it doesn't work then they take it out and hopefully find RAM that will work with your computer.
The types of RAM available are: Dynamic RAM (DRAM) -- this is the conventional RAM most people are familiar with -- Fast Page Mode (FPM) RAM, Extended Data Output (EDO) RAM, Burst Extended Data Output (BEDO) RAM, and Synchronous Dynamic RAM (SDRAM). There is also SRAM or Static RAM which is faster and more expensive. This is used almost exclusively for cache memory. You only have 256K of cache and many motherboards can support up to 512K. If you have a free cache SRAM slot, consider purchasing another 256K.
These new types of RAM use the same trick to reduce the time needed to get the data. In most cases the next item of data the processor requests is right next to the last item requested. Whenever data is requested, the RAM immediately sends several adjacent blocks of data. Unless your computer uses the VX chipset you will probably have to use either DRAM or EDO RAM. SDRAM will be the RAM technology of the next generation of motherboards, mostly because it is capable of working at higher speeds than EDO RAM.
The Pentium and Pentium Pro processors request data in 64-bit blocks. A 72-pin SIMM is capable of returning a 32-bit block. You should always install RAM in pairs, otherwise the processor has to wait while each 32-bit block is read separately.
There is another consideration when buying RAM. Windows 95 can only use as much RAM as the motherboard is capable of caching. Even a motherboard capable of supporting 128Mb of RAM may only be able to cache half this amount.
You must buy RAM that is at least as fast as your motherboard can use. Faster RAM can work in a slower motherboard but will provide no performance gain.
- Roy Chambers