I am thinking that I have a dual 450 Matrox card right now. I use the Matrox supplied drivers (you might want to look into their drivers too).

I am told that there is now a three headed Matrox card out. I am quite tempted to go pick one up. My extra monitor on my desk is on my OSX box and I just don't use it enough to justify it having a dedicated monitor.

I think Xinerama is just slow. Matrox is the best-supported card by X, AFAIK, without using commercial servers or binary (nvidia) drivers.

It's not cheap (around $350), but the Matrox Parhelia is the fastest duel card around. This thing can even handle triple displays if you really wanted to get nuts.

Forgot to mention, the linux drivers aren't out yet, so you'd have to wait a bit.

I like how they have screenshots of their 10-bit-per-color-channel technology. :(

oh... my... god. What marketing retard came up with THAT idea?

Ignoring the fact that you can't show a screenshot of that, 1) they're highly-compressed JPEGs, and 2) they're small pictures.

Grrrr.

Are they the matrox drivers with HAL, or without? HAL is binary only, but it has better support for xinerama. I didn't notice dual screens being any slower on my G450 for the short period of time when I had two monitors...

I didn't have any performance problems with my Matrox G550 Dual-DVI, but maybe you're doing more demanding things, or something. It's fanless, which is a quiet-pc bonus.

I believe Xinerama always runs unaccelerated, so you'll never be able to take advantage of you graphics hardware with it. I run two heads without Xinerama; you get acceleration on both, and the only thing missing is being able to have a single window spanning both monitors, which is a dubious feature at best. (And you can't move windows between monitors, but I pretty much never want that: I just launch them on the right monitor in the first place.)

How do you get mouse travel between them? xtox? Do they share the copy/paste buffers?

X already knows how to do the mouse-transit thing, that's what the LeftOf/RightOf directives in ServerLayout are for:

/etc/X11/XF86Config-4:

Section "ServerLayout"
	Identifier     "grendel"
	Screen         "Screen 0"
	Screen         "Screen 1" LeftOf "Screen 0"
	InputDevice    "Mouse0" "CorePointer"
	InputDevice    "Keyboard0" "CoreKeyboard"
EndSection

Section "Screen"
	Identifier "Screen 0"
	Device     "GeForce2"
	Monitor    "Monitor B"
 ...
EndSection

Section "Screen"
	Identifier "Screen 1"
	Device     "Matrox Primary"
	Monitor    "Monitor A"
 ...
EndSection

Another thing to keep in mind about the G400 (I have a G450) is that both heads are not created equal: head 0 has more capabilities. In particular only head 0 has the ability to do gamma fading, PseudoColor, or DRI. And without DRI, OpenGL runs slow.

I have my system set up to be 24 bit TrueColor on one head and 8 bit PseudoColor on the other (helps debugging xscreensaver a lot) and I ended up getting a second video card, and just not using the second head of the G450 at all, because it was impossible to get the 24/8 thing working with the G450 and have accelerated GL on the 24 head at the same time!

Stupid.

Anyway, I commented out Option Xinerama and things are good now, except a certain web browser refuses to run on two heads at once with the same profile. *sigh*

All's fast now, though, so I'm happy enough.