Tri-Head with HD4890 and HD3300, possible?

[schischa]

hi there,

actually I use a nvidia 8800gt with a 23" samsung (2048x1152) and 22" LG (1680x1050) with xinerama. I also have a HD3300 onboard and a spare samsung 19" (1280x1024). I am thinking about buying a new (faster) graphic card and it would be nice to use 3 monitors at once as one big desktop.

I just read that with the new experimental RadeonHD its possible to use DRI with r600/700 chips. Even if the performance isn't that good at the moment that wouldn't matter that much. As time goes by it surely will increase. The higher performance of the card is needed for windows only. I just need marginal DRI support in linux. much more important is the possibility to use 3 monitors as one big desktop with the two specified cards and the radeonHD driver as I spend most of the time in a linux environment. I don't want to use fglrx btw!

is that possible with radeonHD?

[rohcQaH]

IIRC multi-card Xinerama setups are currently broken in Xorg, due to the transition from Xinerama to XrandR. It should work again once VGA arbitration is in place.

That's all just deductions from posts I read somewhere else, it may or may not be true and I haven't actually tested any of it. It's an uncommon setup, unfortunately.

[schischa]

mhm, I thought it would be a more common setup using 2 GPUs from the same vendor than mixing nvidia and amd/ati actually...

I am just looking for the most comfortable way of using 3 monitors simultaneously and thought that with 2x amd/ati it should work. I also read about mixing nvidia/ati and that it could work with some xorg.conf hacking, but I wanted to avoid that if possible :/

[rohcQaH]

mixing nvidia's binary drivers or fglrx with anything else is pretty much a no-go. But it should be possible to mix ATI+nVidia if you use open drivers for both. As you suggested, two similar cards using the same drivers are most likely to work.

The problems I was hinting at are not due to driver incompatibilities though, but due to (temporary) breakage in Xorg when addressing multiple GPUs. I'd suggest to fall back to Xorg 7.2 (or something), but I'm not sure if the latest radeon or RHD work with that.

You may end up having to try it yourself. Unfortunately, bugs don't get fixed if nobody reports them. The less painful (but more expensive) solution is a TripleHead2Go, or waiting until there's eyefinity-support on linux for evergreen.

[schischa]

have you got any information when the temporary breakage in xorg is going to be fixed? it wouldn't be a problem for me to run a dualhead with one GPU first as long as I have the option to run tri head in some weeks ;)

[rohcQaH]

as said, I believe VGA Arbitration (http://www.phoronix.com/scan.php?page=news_item&px=NzQ4Nw) to be the key. It's in XServer 1.7 and Kernel 2.6.32. Depending on your distribution, you'd have to manually upgrade.

Again, I might be entirely wrong about any of this.