New Q9550 CPU causing otherwise stable system to freeze/hang

You might need a bios update for the 750i, I know when 750i came out they didnt play nice with any quads over q6600.

Set the ram specs manually in the bios, they might be under volted by default.


Since it works with old CPU you need a bios update almost for sure.

I should've mentioned this in my first post, but I did update to the latest bios (1101) shortly after putting the new CPU in. I read where people using a different Asus board were able to overcome similar problems by reverting to an older bios, but haven't tried that yet.
I did try it after setting the voltage and CAS latency to the factory specs (5-5-5-15 @2.1 volts)
Memtest wouldn't complete, as the system would freeze after about 5 - 10 minutes after loading no matter what I tried to do.

I just ran memtest86 (using my old dual core) with no issues. At least I don't think there were.
I burned the ISO image, and booted from the CD. It ran a test, but before I could see what it was doing started booting into windows. Is this what was supposed to happen?

I see now, I was using memtest86, not memtest86+. I just finished running the + version and passed with no errors.
I'm thinking that I'll need to RMA the CPU, but I'm definitely open to any suggestions.

I have the voltage for my ram, and CPU set. I wasn't planning on overclocking, so I didn't go far over the minimum specs though.
2.11 volts on memory
1.3 volts on the CPU
Couldn't find the specs for how I should set my fsb, and didn't really want to mess with that withoput knowing.

Thank you very much for the suggestions everyone (and to saro58 for validating this issue). I've been doing a lot of reading through forums, and elsewhere, and have been learning alot, but no matter what I do in the BIOS I'm still having this issue.

I've tried different memory ratios for my FSB, I've even underclocked my CPU, but haven't found any solution, the system even freezes in my BIOS lately.

Right now, these are the main settings I have setup:

Voltage control:
Vcore: 1.25
DRAM: 2.21 (tried 2.11 for awhile too)
HT: Auto
NB: Auto
SB: Auto

FSB&Memory configuration
Clock mode: Linked
Ratio: 5:4 (tried 1:1, 3:2, maybe others too)
FSB(QDR) 1333
Actual QDR 1333
Actual Mem 1066.7 (with other ratios tried at 800 too)

CPU confuguration
Auto Thermal Control: Auto
Limit CPUID MaxVal: Disabled
Enhanced C1: Enabled
CPU C State Capability: Disabled
Execute Disable bit: Enabled
Virtualization Technology: Enabled
CPU Multiplier: 8 (tried 8.5 first, but thought underclocking could work)
Enhanced Intel SpeedStep Tech: Disabled

Other settings (was in a hurry to get to work and can't remember where these were found off the top of my head)
LDT Freq.: 4x (was at 5x by defazult but I thought that might be high)
All Spread Spectrum function disabled
Mem Timing: 5-5-5-15-2T - those are factory specs, but I tried 4-4-4-12 after seeing it recopmmended on another post, still no love - It's back on factory specs now
Advanced Mem timing all on Auto

I'm really at a complete loss here, and will greatly appreciate any help I can get. I hear the P5N-D can be pretty picky, and am worried it might need to be replaced.

Sort of... I meant to delete the PNY 8800 GT from this thread but forgot.

I did buy the 8800GTS months after buying the 8800 GT (mistakenly), but with my old dual core I did have them running together with the SLI bridge (maybe not correctly though- was told that it probably dumbed down the GTS so that it could run with the GT) - there weren't any issues when I ran them together on the dual core.

Nonetheless, I never did try them both with the quad core, I'm only using the 8800 GTS at the moment.

Not a problem... thanks for checking!

After more testing and reading, my conclusion was that the problem was with my mobo too, or just the 750i in general. Where the mobo was over a year old, and I couldn't afford a new one, I just returned the CPU for a refund (minus the 15% restocking fee).
I'm just gonna give it some time, save some cash, and then start building my dream machine!