Bad Pixels - Kernel, Driver, or Card? [SOLVED]

EMan32x · n00b Joined: 08 Mar 2005 Posts: 14

I have an AMD Athlon 64 3200+ with 1 gig of ram. On it is an NVidia Geforce 5200 Ultra with 128 mb of memory (this is an AGP card succesfully being detected at PCI:0:1:0).

It is a dual-boot Windows XP/ Gentoo 2.6.9-r4.

When I boot in Windows, everything is fine (well, as far as this problem goes.) When I boot to the linux prompt, everything is fine... but when I issue "startx" (which loads kde from an XSESSION variable) many pixels become corrupted. Even as I type this, there are about 3,000 to 4,000 dots on this screen that are green, blue, red, and flashy. They seem to "hug" specific colors on the spectrum - indeed, when I alter my RGB output values through the nvidia-settings utility, the specific pixels that are malfunctioning warp around the screen.

It's far from debiliitating, but it's also extremely annoying.

It has been suggested to me that the cause of the problem is bad memory sectors on my graphics card. I would agree, accept that it runs Windows just fine.

Any ideas?

Looking ahead to potential responses, here is some stuff about agpgart from dmesg:

NeddySeagoon · Posted: Sun Mar 20, 2005 2:12 pm Post subject:

EMan32x,

Several things to be aware of.
Neither Windows nor Linux uses much of your 128Mb graphics. You probably have Double Buffering enabled in xorg.conf (you should do)
So for 24 bit mode at 1280 x1024 you use 2 x 4 x 1280 x 1024 bytes for your pixel buffers.
Thats 2 buffers, 4 bytes per pixel (32 bits) x number of pixels.
Windows and Linux may well put the pixel buffers is different places in the pixel buffer, so it could be faulty memory.

Try different resolutions and different colour depths and even the nv driver and report what effect that has on the symptoms.

You don't say if you are an Analogue (15 pin Dee type) or DVI interface to your LCD. Thats important too.
If you are using the analogue interface, the signal has to be digitised for display on the LCD again. The Video card and LCD are not synchronised, so you see the effects of sampling error as you report. Often in vertical lines down the screen. It can often be reduced by defining your own mode line and playing with the dot clock. For testing, play with xvidtune, which lets you adjust everthing except the pixel clock.

Its worth trying the DVI too.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

EMan32x · n00b Joined: 08 Mar 2005 Posts: 14

I swapped out the DVI cable for the 15-pin blue cable. Some weird things happened, but it did fix my problem! Thanks!

As for the weird things... well, for one, the monitor is displaying things in a really funky way now. Everything is blurry, except that I can't seem to get past in my head that the problem is actually that it's too sharp. This font right here is almost painful to look at.

Also, two strange monitor-integrated dialog boxes popped up while I brought up my system. During coldplugging, a monitor-box came up saying I should increase my resolution to 1280x1024. The startup console is indeed at a ridiculous screen resolution for me, probably 800x600 (on this giant monitor, that means something like 3/4" letters).

Then, when booting X (at the nvidia splash screen), A monitor dialog box says "Adjusting Display Properties" or something very similiar to that. I believe that that box was the start of my troubles.

Any ideas about that one?

I should also mention that all the colors seem very changed - I think saturation has been increased. I played with nvidia-settings a bit, but the problem seems to be more deeply rooted than that.

Edit: After splitting my Red-Green-Blue settings, the colors and contrast have been fixed. Sharpness problems and weird warnings persist, though.

NeddySeagoon · Posted: Sun Mar 20, 2005 6:26 pm Post subject:

EMan32x,

Sharpness problems are caused by running the LCD at some resolution other than its 'native' resolution.
Colour depths should not cause any issues.

What anti-aliasing do you use?
There are several special sub-pixel anti-alising schemes for LCDs. Choose the one that matches your pixel layout.
Its harmless to use trial and error.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

EMan32x · n00b Joined: 08 Mar 2005 Posts: 14

I'm thinking you're almost certainly right. This looks like an anti-aliasing problem.

Thing is, I have no clue how to tell what anti-aliasing I'm using or how to change it.

Sorry! Thanks for all this help.

NeddySeagoon · Posted: Sun Mar 20, 2005 6:44 pm Post subject:

EMan32x,

GNOME has a preference setting for this under Desktop Preferences -> Font.
If you are not a GNOME user, that won't help.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

EMan32x · n00b Joined: 08 Mar 2005 Posts: 14

Thank you very much for all of your help! I believe this has solved all of my (current) problems. The colors are still strange, but I can fiddle with them until they seem better.

I use KDE, but I've been to use nvidia-settings to get the sharpness to an agreeable level. I'll look for font anti-aliasing, but it's all minor fixes now.

Switching to (SOLVED).