I’ve just upgraded my Dell PowerEdge T105  from Debian/Lenny to Debian/Squeeze. Unfortunately the result of the upgrade was that everything in an X display looked very green while the console display looked the way it usually did.
I asked for advice on the LUV mailing list  and got a lot of good advice. Daniel Pittman offered a lot of great advice.
The first suggestion was to check the gamma levels, the program xgamma displays the relative levels of Red, Green, and Blue (the primary colors for monitors) where it is usually expected that all of them will have the value of 1.0. This turned out to not be the problem, but it’s worth noting for future instances of such problems. It’s also worth noting the potential use of this to correct problems with display hardware, I’ve had two Thinkpads turn red towards the end of their lives due to display hardware problems and I now realise I could have worked around the problem with xgamma.
He also suggested that it might be ICC, the command “xprop -root | grep -i icc” might display something if that was the case. I’m still not sure what ICC is about but I know it’s not set on my system.
The next suggestion was to use the VESA display driver to try and discover whether it was a bug in the ATI driver. It turned out that the VESA driver solved that problem, I was tempted to continue using the VESA driver until I realised that the VESA driver has a maximum resolution of 1280*1024 which isn’t suitable for a 1680*1050 resolution display.
After reviewing my Xorg configuration file Daniel noted that my frame buffer depth of 16 bits per pixel is regarded as unusual by today’s standards and probably isn’t tested well. As 24bpp is generally implemented with 32bits for each pixel that means it takes twice the frame-buffer storage (both in the X server and in some applications) as well as twice the memory bandwidth to send data around. So I generally use 16bpp for my systems to make them run a little faster.
(II) RADEON(0): Not using mode “1680×1050″ (mode requires too much memory bandwidth)
I tried using a depth of 24bpp and then I saw messages such as the above in /var/log/Xorg.0.log. It seems that the display hardware in my ATI ES1000 (the on-motherboard video card in the Dell server) doesn’t have the memory bandwidth to support 1680*1050*24bpp. I tried using the gtf to generate new mode lines, but it seems that there is no 24bpp mode which has a low enough vertical refresh rate to not exhaust memory bandwidth but which is also high enough for the monitor to get a signal lock.
My current solution is to use 15bpp mode which gives almost the same quality as 16bpp and uses the same small amount of memory bandwidth. It seems that 15bpp doesn’t trigger the display driver bug. Of course one down-side to this is that the default KDE4 desktop background in Debian seems perfectly optimised to make 15bpp modes look ugly, it has a range of shades of blue that look chunky.
What I really want to do is to get a better video card. Among other things I want to get a 1920*1080 resolution monitor in the near future, Dell is selling such monitors at very low prices and there are a bunch of affordable digital cameras that record video at that resolution. Even if I can get the ES1000 to work at 1920*1080 resolution it won’t support playing Full HD resolution video – I can barely play Youtube videos with it!
I’ve previously described my experience with the awful Computers and Parts Land (CPL) store  where they insisted that a PCIe*16 graphics card would work in my PCIe*8 system and then claimed to be doing me a favor by giving me a credit note for the full value (not a refund). This convinced me to not bother trying to buy such a card for the past year. But now it seems that I will be forced to buy one.
What I Want to Buy
I want a PCIe*8 video card that supports 1920*1080 resolution at 24bpp and has good enough performance with free Linux drivers to support Full HD video playback. Also PCIe*4 would do, and I’m prepared to compromise on support of Full HD video. Basically anything better than the ES1000 will do.
Does anyone know how I can buy such a card? I would prefer an ATI card but will take an NVidia if necessary.
Note that I have no plans to cut one of the PCIe sockets on my motherboard (it’s an expensive system and I’m not going to risk breaking it). I will consider cutting the excess pins off a video card as a last resort. But I would rather just buy a PCIe*8 video card.
Note that I am not going to pay cash in advance to a random person who reads my blog. Anyone who wants to sell me a second-hand card must either have a good reputation in the Linux community or ship the card to me on the condition that I pay after it passes the tests.
Update: The first version of this post said that I upgraded TO Lenny, not FROM it.