Memory Timings Explained

Anonymous Reader writes “Nowadays it seems like everybody is tweaking their system. Something that is of importance in your system’s performance is memory bandwidth, which is directly related to the bus speed. This is a rather confusing thing, sometimes a lower bus speed with faster memory timings is considerably better than just increasing your bus speed. When you are buying memory you want to get the highest bandwidth required by your system with the lowest CAS/tRCD/tRPD/tRAS. If you are operating your system at a 400MHz bus rate then you need at least PC3200 memory and perferably with a CAS specification of 2. If you are overclocking your system to 500MHz, for example, bus rate then you need on the order of PC4200, but as you start shopping for the higher bandwith memory, which will run at higher bus frequencies you will find that in order to get memory modules to run at the higher bandwidth – the manufactures have to numerically raise the CAS latency, typically to 2.5 and 3 in order to produce the modules with bandwidth at an affordable price. As you can see the bandwidth to CAS relationship does not play in your favor unless you want to pay high prices for memory. As you can see the performance hit you take from CAS 2 to CAS 3 is 33 percent, but on the other hand if you can run a front side bus of 500MHz then you have gained a complete system performance increase of 25 percent, so with the complete system operating 25 percent faster it makes up for the 33 percent loss in the CAS latency for most applications.

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