Quote Originally Posted by burningrave101 View Post
Here is my hardware config and overclock related BIOS settings:

Code:
Gigabyte EX58-Extreme (flashed to F4m)
i7 920 3837B075
2x3GB Corsair Dominator 1600Mhz (white slots)
Sapphire 4870x2

Turbo: Disabled
HT: Enabled
Intel power seaving features: Disabled

CPU multi 19x
BCLK 205Mhz
Uncore 17x
QPI multi 36x
Memory 8x  (1640Mhz) 8-8-8-24-1T

Performance enhance: Turbo

vCore 1.35v (1.296v load CPU-Z)
QPI 1.36v
DRAM 1.66v
CPU PLL 1.88v
QPI PLL 1.3v
IOH Core 1.3v
ICH I/O 1.6v
ICH Core 1.2v

PCI-E Frequency 101Mhz
I've tried 203Mhz and 204Mhz BCLK and both times Vista detects 6GB of RAM and I'm running Prime Blend now without a problem. But once I start getting into the 205Mhz+ I start having issues with stability and Windows only detecting 4GB or less.

I called Gigabyte tech support earlier but the lady I got wasn't really any help. She said it was probably my CPU because of the memory controller and at 205Mhz it's pushing it past it's limit. That's kind of what I was thinking it might be but noone else seems to be mentioning Vista detecting less RAM when you clock too high. And going from 204Mhz stable to 205Mhz isn't exactly a quantum leap lol.
A couple of things stand out there.

Your vcore load voltage is a bit low. You should target for 1.36v full load, with your QPI/VTT at just a notch higher at 1.375v. The ICH Core is a bit high as well and that can cause instability. Also, drop the uncore to 16x. It's way more forgiving. If you're using the turbo performance mode, set it to standard which is just effectively changing dropping the Perf Level. You lose a bit on bandwidth, but make it up with the higher blck.

I post up and bench with 215x21 by only adjusting the vcore, dram and vTT. Results very, but from my experience with it, those 3 voltages are clutch.