this is the third forum ive been to. hopefully third times a charm.
this is my spec
asus p5nd 750i
2x 8800gt 512mb sli (asus and zotac)
Corsair 2048MB TwinX XMS2 6400 C5 DDR2 5-5-5-18
coolermaster realpower 650w
AC freezer 7
now, the maximum OC i can get is 3.1 ghz here are the settings:
fsb qdr 1378 (344Mhz fsb)
actual mem (688mhz)
the problem comes when i try to OC above this value. when i tried 3.2ghz the pc just freezes up in windows. i tried increasing vcore to 1.225 and vram to 1.87 but still no difference. could anyone explain to me what i might have done worng?
and also if i set fsb:ram = 1:1 i will get actual memory 1378mhz, which is crazy high. is there something wrong with the mobo?
ppl out there are gettin 3.4-3.6 at default vcore so it should be the same for me.
Actually, FSB:RAM 1:1 will make the RAM speed half the speed of the FSB. This is because the FSB is quad pumped, while the RAM is double pumped, so with a 400MHz base clock on both, the RAM should be at 800MHz, and the FSB at 1600. With a 333 base clock, the RAM would be at 667, and the FSB at 1333. So, the first thing to do is set the ram to a slower speed.
tried vcore 1.299 but didnt make a difference.
the problem with the bios is that if i set fsb:ram to 1:1, the value of ram it gives me is equal to the value of fsb qdr, which is 2 times what it should be (ie if i have fsb=333, my actual ram value as displayed in bios will be 1333mhz). with this setting i cant even POST.
but if i used sync mode in fsb:ram it gives me the proper value, which is double the fsb. (ie fsb 333, actual memory value is 667mhz). this setting manages to load into windows and cpuz says tht my mem works at 1:1 and dram value us equal to FSB.
i tried on a different pair of memory just now (2gb OCZ 6400) and it made no difference. so it must be either the mobo or cpu.
any other suggestions? or is it possible my components might be faulty
I think you may need more Power for your computer. I think you should try 750 watts. And is your E8400 a CO or EO stepping?
my 2 x 12v rails only have 18amps on it. so i tried removing one of the gfx cards thats in sli. but there wasnt any difference. it just wouldnt OC past 3.25ghz. these are the settings for my current clock (3.25ghz):
on my attempt to go to 3.3 i had these settings:
sb 1.52, but pc wont post. shouldnt this be enough for a 3.3ghz OC? or should i pump some more juice?
cpuz says its a CO revision. which one is a better OCer?
alright. after raising the NB and SB voltages to 1.36 each and vcore at 1.28, i managed to get 3.4ghz. tested orthos for an hour and a half, no errors. so far no freezes whatsoever. thanks for the tip guys.
so to sum it up, when OCing raise every voltage up notch by notch untill u get a stable OC. hope this thread will be helpful to others.