DDR3 Speed vs. CPU FSB, help!

[Cray25]

I just recently bought a brand new computer. My specs are:

Asus Striker II Extreme (Mobo)
Intel E8600 Processor (3.3 Ghz stock)
OCZ DDR3 1333 Mhz

I want to overclock the processor to at least 4.0 Ghz. Ive been doing some reading and i found out that Intel CPUs are "quad pumped", meaning that the 1600 FSB that i get from overclocking to 4.0 Ghz is actually 400 FSB. I also read that DDR3 is "double pumped", meaning that my DDR3 1333, is actually at 666.

My question is: If my CPU's FSB is 400 Mhz when i overclock it, how does it make use of the extra FSB of my RAM, which is 666? Would i have to push my CPU's FSB up to 666 in order for it to run at 1:1 with my ram? I dont understand why DDR3 is rated to run at such insanely high frequencies, i've seen some DDR3 sticks that run at 1600, 1800, and even 2000 (800, 900, and 1000 before "double pump"). Does this mean that ill have to boost my CPU's FSB up to 800, 900, and 1000, in order to make use of the full capacity of DDR3? Or do i have to run the FSB and RAM at something other than 1:1? Whats the point in having so much head room with DDR3?


Thanks for the help


Sorry for the double post

[jason4207]

Yeah, you have to run a different mem divider. In theory (1 of my old theories, anyway) you will be choked by the FSB when you run anything besides 1:1. However, after some experimentation I've had great bandwidth increases (as seen in the Everest benchmark) using higher mem dividers. However, it has also been shown that the additional bandwidth does nothing for most applications. Its good for benchmarks, and makes your e-peen a little larger, though!

A lot of folks use the 2:1 divider w/ DDR3. The 790i boards are supposed to be good at OCing RAM, so personally, I'd see what they can do!

DDR3 and even some DDR2 RAM speeds have surpassed useful bandwidth for 775 CPUs (thats just technology moving at different rates), but the i7's can make much better use of the additional bandwidth that DDR3 is capable of.

[Cray25]

Yea, i think im gonna have to use a 2:1 divider but that leads me to another question..

Since my processor runs at 3.3Ghz (333 base FSB). I was wondering what would happen if i installed DDR3-1600 (800 with out "double pump"). Would the ram speed (800) come down to match the FSB speed (333)?

If i overclock the cpu's base FSB to 400Mhz with the ram at 800, then i could run a RAM:FSB ratio of 2:1. But what happens if i dont overclock and keep the FSB at 333Mhz and the ram at 800Mhz? Is it gonna automatically use some weird divider (800/300)? Would that affect the performance?

Thanks for the help

[Evilsizer]

Yea, i think im gonna have to use a 2:1 divider but that leads me to another question..

Since my processor runs at 3.3Ghz (333 base FSB). I was wondering what would happen if i installed DDR3-1600 (800 with out "double pump"). Would the ram speed (800) come down to match the FSB speed (333)?

If i overclock the cpu's base FSB to 400Mhz with the ram at 800, then i could run a RAM:FSB ratio of 2:1. But what happens if i dont overclock and keep the FSB at 333Mhz and the ram at 800Mhz? Is it gonna automatically use some weird divider (800/300)? Would that affect the performance?

Thanks for the help
that is what the ram ratios are for... that way at 333fsb you can run your ram at spec. using DDR2 as a example, if you were running 333mhz fsb cpu. on a 1:1 ratio that would be ddr2-667 the higher the ratio the faster the ram speed.

jason,
i know you said 780i but when talking about using DDR3. Did you mean the 790i board?

[jason4207]

^^ fixed to 790i (thanks!)

Yes, your board will start choosing weird dividers, and some of them won't work well. I don't know a lot about nVidia boards, but I would try to keep the dividers somewhat even.

Remember that you don't have to run the RAM at exactly its rated speed. Its not gonna break unless you start cranking the volts to it.

[kkpudge7]

Ok, I think this may be where my problem is at. I'm trying to get my FSB to 400, but I'm using an Asus P5E3 Premium. I don't see a divider setting in my bios. How do I set this?

My ram is 1600 (running 800 double pump as I understand it), and with the CPU being 400, I would need a 2:1 correct?


EDIT:

I think after about a week of heavy research I figured it out on my own! :D I set my DRAM frequency to auto, set FSB to 400Mhz, and enabled X.M.P

I've been stable in large fft for almost 10 minutes, and I couldnt get it to go past 2 before. My p95 temp is 55c on the hottest core. Not too bad I guess for 3.2Ghz