Overclock OK w/ integrated graphics, no post w/ PCI-E video?

[sniperruff]

Just trying to squeeze more out of some old tech:

Mobo: Biostar P4M890
Integrated GPU: S3 Unichrome
CPU: Celeron E1400 (2.0ghz)
Ram: 2x 2gb Corsair XMS2 800mhz DDR2

I had the E1400 OC'ed to 2.4ghz (240mhz FSB) without problems running integrated GPU, but after I installed a Radeon 4350 it won't post (stuck while loading BIOS). Same thing happened when I swapped the 4350 for an Geforce GT220. The highest E1400 will go with a PCI-E video is 2.2ghz (220mhz FSB).

I swapped the E1400 for a C2D E6600 (2.4ghz, 266mhz FSB). I pushed the FSB to 300mhz (2.7ghz) WITH the PCI-E video and it won't post and gave me a LONG beep on boot. The highest stable FSB is 280mhz (2.52ghz).

Took out the PCI-E video (running on integrated GPU) and pushed the FSB to 300mhz and it boots and is stable! What gives?

I think I need to lower something on the PCI-E when I pushed up the FSB. Anyone knows what?

 

[Schmide]

There should be a pci bus frequency select in bios. It needs to be set to asynchronous or fixed (i.e. 100mhz).

 

[sniperruff]

There should be a pci bus frequency select in bios. It needs to be set to asynchronous or fixed (i.e. 100mhz).

Not with the PC right now, but I vaguely remember being able to set PCI-E frequency. Should I bump it up or down (I think the default is 100mhz)?

 

[Jen]

Not with the PC right now, but I vaguely remember being able to set PCI-E frequency. Should I bump it up or down (I think the default is 100mhz)?

should be fixed at 100 ,

Jen

 

[Zap]

I think the PCIe bus is only partially locked with those VIA chipsets. I had a similar problem way BITD with a P4 on a VIA chipset motherboard. It basically wouldn't go above the highest "official" FSB supported by the chipset or else I had issues. My "fix" was to get a lower FSB CPU with a low multiplier and overclock it to the higher official FSB.