Oc'ing problems with A7N8X

I have an unlocked XP1900+ and did some experimenting with oc'ing today. I set the multiple to 9.5X and 166 interface, sync and it should read 1577Mhz, but the bios and Sandra reads it as 1245Mhz. Also, 9.5X with 180 is suppose to read 1710Mhz , but says 1343Mhz instead. What could be the issue? Is the weak bios at fault?
11X works (135) as it reads 1.49ghz.
10X and 10.5X won't boot at all.
11X @ 166 booted and read properly as 1826Ghz, but I got a KMODE_EXCEPTION_NOT_HANDLED error.

Asus A7N8X Unlocked XP1900+
512Mb Corsair 3200 C2 5-2-2-2T

Thanks

The bios always shows the mem frequency as 1MHz slower than what I selected during post, but cpu id in windows shows what I actually selected in the bios.

Your multipliers are screwed man, I think you need to go back and re-unlock your CPU. You don't have your 9.5, 10, 10.5s. That means that some bridge isn't properly connect...or PERHAPS the mobo is screwing up...but I dunno about that one.

I have no even mults 'cause my unlock was only partially successful, so I speak from experience.

Do you have 9x mult? 8 or 8.5?

I have 8.5X200 and it's properly reporting the speed! (1692Mhz). Finally. I'm running 5-2-2-2T (DDR 2.8volts) and so far it's been stable through PCMark, 3DMark2K1SE, Sandra and UT2K3.
Sandra Memory Bandwidth 2968/2694 (1 512Mb stick)
PCMark2002 5336/5186/831
3DMark2001SE 12,187 (G4/Ti4200@255\555)
9X133 is reported as 933Mhz. Sandra shows 7X for a multiplier