Overclocking the PCI Express bus on NForce 4 chipset
 

I have a DFI Lanparty NF4 Ultra board and a 8800GTS 512 graphics card. The Graphics card is PCI Express 2.0 but the motherboard isn't. The bios indicates clocks possible from 100 to 145 mhz. I have upped my setting there from 100 to 120. I know that overclocking the PCI-X becare standardized from the NForce 590 series and up, but what should I expect from my DFI board? At 120, I noticed the PWMIC and NF4 chipset is about 2 degrees hotter than before, standing at 56 and 54 respectively.

Any ideas and comments welcome.

Whenever I overclock, I really don't change the PCI express slot until it is needed. Needed is whenever the picture of windows, or your os, is screwy once you get in there..
Also, I won't go above 115 at the most... I don't oc it more then 110 myself. I've heard that on some mobo's at and after 120 you can start to lose your South bridge or display...

I found personally that the PCI express clocks did very little to help until 3.0GHz or better was needed to be stable. I saw no ill effects from doing so, but it can go too high as Cold Storm mentioned above!

Also keep an eye on that PWM temp. I had found at around 60*C stability was lost.

I went to 125MHz before. It worked for a while, then I got dator corruption. I wouldn't go any higher than 110 myself. I like to stay at 103.

Yeah, your right there my friend :toast:. There really isn't any change in your display till you go higher then say 40% oc.. Then you see the difference in speed and so forth. I'd say the last thing to ever change when your ocing is that.

Well I remember in my early OCing days, I used Ntune to tweak my rig once. It sets the PCIe at 117 IIRC on most of the NF4 mobo's, altho I dont know why?!?!

I've also seen with my asus board, I tried the Tweaker... it just for some reason didn't like to use the most extreme oc.. but if you went into bios, and tweaked it a little, you where able to fix it to boot.. But it was the same for me. PCIe that was crazy numbers

So it really affects the southbridge then if I overclock the PCI-E lines? Because, I'm thinking, I have a RAID0 setup using the Nforce RAID. So if the overclock is too much to handle, then I could have RAID issues??? :(

It will drop a HDD on boot most likely causing a boot error. Usually dropping the PCIe speed will bring it back, but there is a chance of corruption, leading to a need to rewrite the OS!

Indeed, plus it won't bring enough performance gain to really matter. It's been found that slightly overclocking the pci-e bus with dual gpu cards helps with performance. 120 really is too much and at that speed can deffinitely lead to HDD and raid problems.

Back in 2006 I had a DFI nF4 LP Ultra and I used to bump the PCIe bus upto around 160MHz when benching graphics. It did allow a higher video card OC - my Radeon X800 went from 615MHz to 660MHz after bump in PCIe. I didn't have any HDD problems.
Since HDD/RAID controller is in the nF4 chipset (southbridge) and not some chip connected to it, there's a lower risk in OC'ing the PCIe. Essentially, on nF4 AMD chipsets PCIe freq only affects devices in PCIe slots and things connected to the SB via PCIe lanes (NICs, Realtek HD audio). HDD controller will be none the wiser about PCIe clock rate.
But I wouldn't recommend to go overboard with it...
:)


PS.
_33,
Hmm... How come we haven't seen you for the past year? Where have you been?
:)

160 for the PCI-E ??? Are you sure because on mine it only goes up to 145 on the BIOS. Unless you had a special one!?

Yes it's me, but I haven't been around because I wasn't much into tweaking my PC at some time. But I am still interested. Plus, INTEL gave a kick in the nuts of AMD with the C2D, and since I didn't have a C2D, I wasn't too thrilled about AMD either... Anyhow, I'm glad to step foot in TECHPOWERUP once more :P

_33,
Yup. I'm sure.
Maybe it depends on BIOS revision?