7900GTX, M2N32SLI Bios question about PCIe settings.

[jpe20]

Hi folks,

I am trying to overclock my system but have reached a brick wall with my 3800x2 AM2 CPU. After ruling out RAM timings etc, HT Bus Freq and other things I have now come to suspect my cause of instability over 2.5GHz is something to do with the 2 7900GTX cards and its associated PCIe bus.

So any graphics card whizzes know about settings for the following in my BIOS....

PCIex_clock_1(2) = AUTO or 100MHz-200MHz
PCIe<->NorthBridge(and SouthBridge) Voltage -> AUTO or 1.2V-1.4V.

I know its technical but you never know!!! I am sure someone has played around with these settings. I have tried setting frequency of the PCIe buses 1&2 to 100MHz and 200MHz (CPU freq=250MHz (x10)). It crashes/hangs in POST on both settings. Does PCIe frequency have to be a certain multiple of the CPU freq. Not tried playing around with the NB(SB)-PCIe voltage settings as I have no idea what to set these to.

Anything else I should know about?????

Jules

 

[maddness]

you should ideally keep pci express clock at 100 fixed or slightly over in some cases. HT multiplier should be set to 3.5 from 5.
Try a bump in Vcore.


What board are you using?

 

[jpe20]

I am using the ASUS M2N32-SLI (603BIOS) mobo. HT is at 4x and PCIe speed is set on AUTO for now. Is there any (free)utility that can report the PCIe bus speed? SiSoft Sandra don't seem to have it. I am starting to think that 250MHz FSB is the limit for my mobo. I have tried dropping down to 3x HT.

Jules