Many questions about RAM/CPU/FSB matching

[robbinsr]

I'm in the midst of learning everything I can about computer hardware, and there are a few things pertaining to memory which I'm still unclear about after reading all kinds of tutorials and whatnot. I was hoping you guys could clear some things up for me . (I have a background in electrical engineering, and alot of my assumptions about computer hardware may be wrong)

From my understanding, the CPU determines the speed at which the RAM will operate via the FSB. For example my E8500 advertises a FSB of 1333, but after doing some reading and messing around in the BIOS I've learned that it's actually 333mHz but that 4 chunks of data are moved on each pulse. I've also learned that DDR memory serves 2 chunks of data per cycle so DDR-667 operates at 333mHz.

Does this mean that DDR2-667 is optimal for FSB of 1333? Or is DDR3-1333 optimal? DDR3-2666?

 

[o1die]

Go by the ram recommendation for the board in the motherboard manual or the spec sheet. Some bios list the actual speed as half (666=1333). cpuz lists the ram speed as half also. I use it alot for identifying old motherboards. For overclocking, most boards will increase the ram speed by the same percentage as the cpu fsb, so I drop the ram speed before increasing the cpu fsb so the net result is the ram running in spec. For example, if I drop 1333 ram to 1066 while increasing the cpu fsb from 200 to 250, the net ram speed is 1333. This won't show up on the post screen for the ram; only the cpu increase is displayed there. Cpuz will confirm the change in ram speed. And it will also show the decreased speed in realtime for the cpu. Cool and quiet and Intel's speedstep software are built into most motherboard bios; these lower the cpu fsb automatically until you load up the cpu with gaming, etc. You can disable this in the bios, but it usually works fine, and saves energy and keeps temps lower when idle.