Black vertical lines in X display [solved]

[jleejj]

Hi all,

Been a while since I posted but this problem has me stumped. I am installing Gentoo on a HP Vectra XU 6/200 (dual Pentium Pro 200Mhz) with a Matrox Millennium graphic (MGA 2064W). I believe it has 8Mb of video memory.

I've installed Xorg and configured it appropriately (I think). However, when I run "startx" my window manager starts but the screen is filled with horizontal black lines. In other words, there is a column of the correct pixels, then a column of black, then a column of the correct pixels ... like it is skipping every other column. The odd thing is that the mouse cursor is not affected by these lines (it being the only thing).

Does anyone know what could be causing this? As a side note, I can't get the X server to change resolution by hitting Ctrl + Alt + "+" or any similar combination. Did they change something in Xorg or is my memory of the keystrokes bad?

I can post my xorg.conf if anyone wants to see it, but this is such an odd behavior that I'm sure I must be missing something obvious.

By the way, framebuffer support on the liveCD worked great so I know the graphics card works in some form.

[Edit] Oops, this should be in the "Desktop Environment" forum.

[NeddySeagoon]

jleejj,

The keystrones for changing resoltions 'on the fly' are ctrl-Alt-+ and Ctrl-Alt-- buut only the +/- on the numeric pad work.

To be able to change resolutiosn yo have to have more than one available. Try the vesa driver if you are not using it already.

The mouse cursor is by default, drawn using hardwar, so its never in the pixel buffer. You can turn that off it if want.
_________________
Regards,

NeddySeagoon

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

[jleejj]

Thanks for the suggestions.

I tried the vesa driver and, although it works as well as the mga driver, it doesn't work any better. I still get every other pixel column. Since the mouse is drawn correctly to the screen, it is obviously not a resolution problem ... so what could it be? Anybody have other suggestions?

[NeddySeagoon]

jleejj,

Heres a long shot for you. You say the graphics card has 8Mb of memory. Is that set in the X config file or do you allow it to be auto detected?

Depending on how the pixel buffer is laid out, if you have specified more graphics memory than you actually have, X will quite happily draw in no existant memory but you will get strange visual artefacts on the screen.

You could try specifiying the amount of graphics RAM (from 8Mb on down) and/or disabling dbe (double buffer extension). You won't like the latter as a long term solution as it forces X to draw in the pixel buffer that is being dispalyed
_________________
Regards,

NeddySeagoon

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

[Deathwing00]

Moved from Multimedia.

[jleejj]

Thanks for the reply NeddySeagoon.

I actually discovered the solution on my own before I came back to check on this thread and your are dead on correct. Actually there were two problems: I had an xorg.conf in /root which I copied into /etc/X11 and continued to make changes to it there. Unfortunately, (as I finally discovered from checking the Xorg log in /var/log ), Xorg was picking up the xorg.conf in /root first and ignoring all the changes I was making to the "official one."

The last change I made to the /root/xorg.conf version before copying it was to manually set VideoRam to 8M (because it appears to be correct from lspci). Obviously, that is not the correct setting. The columns of dead pixels are apparently missing memory locations which the Xorg server writes to but the graphic card can't read. Funny how the result was an interlaced image of missing pixels instead of just half a screen. I wonder if the effect would change when set to 8 bit color .... anyway, changing VideoRam back to be auto-probed and picking some resolutions that could fit in 2Mb of memory solved the problem.