Quote Originally Posted by Thickbrit
Here's a few things i have found with my early dh.Bios 1403 has been the best overclocker for me,seems fairly stable apart from occasional loss of video signal at boot/post.
My board will not boot with memory frequency > 499mhz,or fsb much above 400,so i boot with < 399fsb and < 500mhz memory frequency and then memset trd to 7 and my memory will go to 547mhz 4-4-4-4,but not 1mhz more at any volts/timings/devider.Memory stops dead at 547mhz.This board does not seem to like cas 5 at all,with either of the rams in my sig.
My northbridge (fsb limit) goes to 463 fsb (1m) @ 1.9v on normal water,more volts don't help,did about 414 on stock cooler 1.65v,and about 435 on water and 1.65v.
All deviders seem to work fairly well,except the 3/5 (cpu/ram),which seems unreliable,although i haven't looked too hard for the reason yet.
Lower cpu multi's seem to stress the cpu more,at least on the x6800.
Thats about all i've learnt for now,except for 1 last thing,the fact that asus has the 2nd and 3rd primary ram timings totally reversed to all ram software,is totally confusing,annoying,and unnecessary.
I'm not sure that lower CPU multipliers really stress the 6800 more.
I think what happens is the CPU tries to complete its "power up" routines at the default multiplier (11), before the BIOS even initializes. That's why the X6800 won't post at lower multipliers and very high FSB unless you increase the vcore. The Nemesis already found this out. The vcore increase you need is equal to the vcore needed for posting at the exact same speed you would have if you were using an 11x multi (example: 400 FSBx9=3600 mhz, but would require the CPU to be able to low level POST at 400x11).

That's what I've found out; maybe I'm wrong.

You should be able to test this by using CrystalCPUID to change the multiplier in windows, from your normal stable overclock (let's say you are using 360x10=3600 or 328x11, and then a clockgen or setfsb or whatever to increase the FSB. (goal=400x9?) CPU should still work at the exact same voltage if the mhz remains the same. But it simply won't POST at 400x9 as it tries to post at 400x11.

Multiplier unlocking is done by the BIOS giving a command to the CPU to lower the multiplier, if I recall correctly, not by "writing" a new multiplier into the CPU flash memory or something like that. Otherwise the CPU would keep the lower multplier as default if you switched motherboards, which it does not. (correct me if I'm wrong).

How did I come to this conclusion?

Rather simple, actually.
my X6800 cpu posts and runs fine (dual prime stable) at 360x10=3600, 1.5125v. But put CPU at 370x10=3700, and the CPU won't even POST (which is unheard of for anyone doing a 100 mhz clock higher). If I increase vcore to 1.55v, it posts all the time. 1.575v for stability in windows/games.

That only makes sense if the CPU were actually trying to POST at 4070 mhz (370x11) at 1.5125v, before BIOS takes over and lowers the multiplier.