Comments on: Can I fix these recent horizontal black glitches on this onboard SiS chipset?

Question: Can I fix these recent horizontal black glitches on this onboard SiS chipset?

adamwolf — Tue, 17 Jan 2006 18:46:47 -0800

How can I fix my SiS onboard video? What did I even do to break it? I recently reinstalled my girlfriend's Linux machine, adding a hard drive in the process. For some reason, the display shows horizontal glitches and every once in a while blinks black for a few seconds.

This is onboard SiS video. It is independent of monitor. This sounds quite like video bandwidth issues, but I'm not exactly certain, because of two reasons. The 99% of the time these horizontal black glitches occur during a keystroke. You can tap out a drum solo on the spacebar, and the flickers will follow as well. Is this typical of video bandwidth issues? Another thing is that assuming it is memory bandwidth issues, I decided to set the display to 640x480@8 bits per pixel. Still horizontal glitches. This makes me say it isn't a memory bandwidth issue. Another test I performed was playing a video. The "glitch rate" didn't increase.

The display also blacks out every once in a while for a few seconds. Here's the kicker--It worked a month ago, and she's never seen the glitches before. I haven't really changed anything except I installed GNOME. However, Xfce4 *also* has this problem. I've tried to see if text mode has this problem, but its hard to see the glitches on a black background. X detects ~64 megs of video memory. This *should* be enough by my calculations for 3.5 frames of 1280x1024@16bpp. I've used alternate monitors and alternate video cables.

What would do this? BIOS settings? Was there an Xorg update recently that would break something? I'll accept "random hardware failure" if there are no other choices, but I can't help but wonder. It's extremely hard to work with this machine, and I'd really hate to have to replace it this soon. I've googled with my usually amazing google-fu, but have had no luck.

By: PurplePorpoise

PurplePorpoise — Tue, 17 Jan 2006 19:48:34 -0800

My first impulse is either overheating or overclocked ram.

Are all the fans in the case still working at full speed?

By: purephase

purephase — Tue, 17 Jan 2006 20:01:31 -0800

It sounds like you have a video driver that may not be well supported in Linux. Regardless of the content of the link, have you tried Windows on this machine? Even if it's not permanent (or necessarily legal *ahem*) at least you could rule out the possibility of hardware failure.

By: nickerbocker

nickerbocker — Tue, 17 Jan 2006 20:06:32 -0800

it definitely sounds hardware related. you should try a Linux Live cd like Ubuntu live, or Knoppix just to make sure.

You could have damaged the video via ESD, Electro-static discharge. Although, that is unlikely. Is buying a replacement video card an options? You can find some pretty cheap AGP and PCI cards out there.

By: adamwolf

adamwolf — Tue, 17 Jan 2006 20:44:16 -0800

I thought you had it! This machine has had heat problems in the past. I underclocked the processor to the place where it behaved perfectly properly for a year, and the flicker was replaced by the aformentioned black screen. These were longer, and the monitor tells me it isn't receiving any signal during these lapses.

After running 10 minutes, the processor temperature was 38 degrees C, just fine.

I played with memory timings. No dice.

By: adamwolf

adamwolf — Tue, 17 Jan 2006 20:58:16 -0800

The machine worked great in Linux before Christmas break.

By: SpookyFish

SpookyFish — Tue, 17 Jan 2006 21:26:46 -0800

Perhaps the power supply is weak and the new hard drive pushed it over the edge?

By: Pryde

Pryde — Tue, 17 Jan 2006 22:06:53 -0800

I'd say go with the LiveCD suggestion, preferably one that's not using the same version of Xorg (just to be on the safe side).

You could also try disconnecting the new hard drive.

By: hattifattener

hattifattener — Wed, 18 Jan 2006 00:57:58 -0800

You say you've tried swapping out the monitor and the video cable, but I'm still wondering if it's some really simple hardware problem. The glitches get worse when you type; what if you just tap the desk next to the keyboard (or tap the keyboard itself but not on a key)? What if you wiggle the monitor or keyboard cord? Etc. From what I know of PC architecture, there shouldn't be a reason that keyboard input would affect the video hardware, but there are many mysteries I am not privy to.

I'd also try finding some text-mode program that fills the screen with reverse video so you can check if the glitches occur in text mode.

By: adamwolf

adamwolf — Wed, 22 Feb 2006 19:00:03 -0800

I solved it! xscreensaver 4.23 causes those black lines. More information available at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=336368

It can be solved by upgrading to xscreensaver 4.24.