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CPU/FSB Speed Vs. Memory Speed

Last response: in CPUs
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August 8, 2008 9:04:34 PM

Hello everyone,

I have a question about which kind of memory is really going to be the best one for me. Im planning on buying a XFX nForce 790i Ultra SLI Motherboard, its specs say its FSB is 1600MHz

Intel Core 2 Duo E8500 Processor is what im going to use for the moment on it and it has a Bus speed of 1333mhz.

So the question is..the specs say the motherboard is capable of supporting 2000mhz memory speed, is the access speed of the memory caped at the CPU speeds 1333mhz or will i bottle neck putting 2000Mhz or 1600Mhz memory inside it?

August 8, 2008 9:37:49 PM

As long as you are running your memory in dual-channel mode (essentially, installing DIMMs as pairs), the memory bus throughput will be 2x the module speed. For example, running your modules at DDR3-800 will give 1600MHz throughput. Since all data to/from RAM has to go through the FSB on current Intel systems, whichever has the lowest throughput between the FSB and memory bus will limit your memory performance. Since your E8500 uses an FSB of 1333MHz throughput, that will bottleneck your memory performance for any memory bus speed of DDR3-667 or faster. That's why DDR2-800 RAM is still plenty fast enough for today's and tomorrow's Intel CPUs. DDR3 RAM's speed won't be used or needed for a while yet. If you do decide to buy a DDR3 motherboard, just get the cheapest, slowest DDR3 modules you can find.
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