I just switched from an ASUS m2npv-vm to a DFI LanParty Jr 790GX. I'm running an AMD Athlon 64 X2 4000+, and a NVIDIA 6200 LE card on both.

Well, for some reason, Xorg uses 20-50% of my CPU on the new DFI board. It does this during unpredictable moments. For instance, if I run super-pi, it will do this; however, if I run "stress", SciMark, or byte, it's perfectly fine.

Xorg never used nearly this much CPU on my old board, so I never had a problem with it, but I think it might be the fact that I run two xscreens to watch video on my TV. Yeah, I know about TwinView and Xinerama, but I like two xscreens more, because TwinView doesn't handle full screen video as well.

I can't figure out why Xorg would just suddenly decide it needs to us much more of the CPU though. I'm using the exact same driver, kernel, and distribution that I had, the only difference is the hardware.

I was thinking that perhaps since I'm using an AM2 chip in an AM2+ board, it was the backward compatibility causing it to be sluggish, but I ran some benchmarks that showed otherwise, and indicated that with Xorg turned on was the only time it was sluggish.

So now I'm thinking that for some reason Xorg isn't utilizing the video card GPU as much as it should be, and using the CPU for taking up the slack.

I don't know how to test any of this though, so it's all just speculation. Hopefully someone can tell me some things to try.

Here are some hard numbers...

I compared some benchmarks between a guy with a 4000+ running at stock and essentially the same system, aside from a minor kernel upgrade and a different chipset ( which may be the problem anyway ).

Phoronix Global - work-28.10.2008_13:44 Testing

02-04 are mine, and as you can see on 03, while running a LiveCD, I get much better performance on super-pi than with Xorg and the nvidia driver running. Even OC'd .5-1 Ghz over stock, I can't even compare to the stock time it takes for 01 to run super-pi.

What's worse, is that an OC from 2.6 to 3.0 Ghz only netted me about a second on super-pi.

Clearly something is not optimal here, but I don't know what. Could running two xscreens really be the problem, and why wasn't it a problem for my old motherboard? TwinView does not offer any improvement, but I did not try a single screen because this would defeat the purpose of this rig, and judging by the LiveCD, either the NVidia driver or Xorg is the cluprit. Why would it only become an issue with this newer board?

I just ran a head-to-head comparison between the NVIDIA driver and the nv driver. There is not a significant difference that I could see. Could this narrow it down to Xorg? If so, how would I go about updating or upgrading Xorg?