View Full Version : [all variants] Getting Dual-Head, "Big Desktop" Working

January 9th, 2010, 02:19 AM
Recently I installed an ATI Radeon HD 2400 Pro 256MB PCI card in my new-to-me Dell PowerEdge 1600SC. Next I planned to upgrade my 19" flat-screen LCD monitor to a 24" wide-screen version, when a friend suggested that, for the way I mostly would use the system (software development and the like), I'd be better-off with two 19" monitors, because I'd have more screen real estate. Well, since I already had a matching 19" monitor, that'd certainly be a lot less expensive, so I figured I'd give it a go.

I should note, at this point, that I'm using ATI's proprietary fglrx driver.

The first problem I ran into was attempting to use ATI's amdcccle (Catalyst Control Center) utility. It didn't see the monitor hooked-up to the card's VGA connection. So I ran aticonfig --initial=dual-head --screen-layout=right and that got the ball rolling: Now I had two separate desktops. Then I simply went back into amdcccle and enabled Xinerama. (There was some re-starting of X involved in there, somewhere, I'm sure.) Voila! I had what I wanted!

Or so I thought.

I was then informed by an on-line colleague that direct rendering would be disabled with Xinerama enabled, slowing-down rendering. Didn't want that. So off to figure out how to get it working with Xrandr.

A couple hours later, and none the wiser, I finally put-together bits and pieces I found elsewhere on the web and did this:

Restored the /etc/X11/xorg.conf I'd had before running aticonfig the first time. (Always make sure config files are backed up somewhere before embarking on an adventure like this!)
Ran aticonfig --initial -f
Edited /etc/ati/amdpcsdb and, in the section [AMDPCSROOT/SYSTEM/DDX], added the line EnableRandR12=Sfalse
Edited /etc/X11/xorg.conf and in the Devices section added Option "EnableRandR12" "false"
At this point I had cloned screens
Ran aticonfig --dtop=horizontal
Re-started X by logging off and back on

Done! I have just what I wanted and, according to glxinfo, I have direct rendering.

Hope this helps somebody else!

An amusing side-effect of this configuration: My screen-saver displays a bunch of pictures that my wife, I and friends have taken over the years. Now, when it kicks-in, each monitor displays a different picture at any point-in-time. :)


January 9th, 2010, 06:53 AM
Kudos! In my experience, just getting dual head to work with ATI was a huge pain.