Re: Advice on dual head cards

[Helge H. <hel...@ai...>]

On Fri, Oct 22, 2004 at 03:40:45PM -0500, Observer wrote:
> I want to have independent users per displays, is this what you
> succeded?.

Yes.  The G550 (and some other matrox cards) have kernel framebuffer
drivers that gives us two framebuffers, one for each head. 
I've been able to run an accelerated server that access
one framebuffer (using the mga driver), and an unaccelerated one that 
access the other framebuffer (using the fbdev driver).

This works fine, and the unaccelerated driver is fast enough for
office work and 2D games.  The accelerated driver support 
accelerated 3D too.  

I've been able to run two independent accelerated drivers on the 
G550 too.  They ran on the same head, but clever use of
"scrren 0", and "screen 1" should be able to run them on
separate heads - giving accelerated 2D on both heads.  I didn't
research this further, because using 3D acceleration with
one xserver froze the other accelerated xserver for the duration
of the 3D game.  That isn't useable beaviour for me, so I
didn't bother experimenting further.  

> Accelerated X is preferred but not required.
You _may_ be able to get accelerated X on both heads of a matrox
dualhead card - it will take some experimentation.  It doesn't seem
likely with others.  I know of no other card that support
dual framebuffers the way matrox does, so even unaccelerated
dual X seems unlikely with other cards.  

Note that multiple accelerated X isn't that hard if you go
for one screen per card.  (Yes - you'll use lots of
pci slots that way).  You have to look at compatibility,
as only some cards work in such configurations.  But those
that do should be fine.  You may even get 3D acceleration
on several cards.  

I have tried G550 AGP+Radeon 9200SE PCI.  I get accelerated
X on both, and accelerated 3D on both.  Unfortunately, the
radeon isn't entirely stable, particularly not when using 
24-bit color and 3D.  (The G550 is stable with 16-bit color,
hopeless with 24-bit.)  The Radeon PCI 3D is also rather slow,
a "known problem" for the DRI people.  It is enough
for tuxracer at 640x480 though.

Using a bunch of matrox cards (one AGP and the rest
PCI) is supposed to be a good solution, not the latest
matrox cards though - newer cards perform succesively worse
because matrox no longer release enough documentation for
free software driver writers, and they don't release much in
the way of proprietary drivers either.


> I want to do it cheap, i think the cheapest dual head card are sis
> xabre, but i want to make the less possible attempts, so i would like to
> know of existent working configurations, I read in the list that there
> is a list of supported hardware and a db of ruby users but I cant found
> them, does anyone have them?
>
Not me, I mostly know what I have tried.  Search archives for
this list - there are quite a few success reports.  Note that
multiple accelerated 2D is what any old report is about,
success with multiple 3D acceleration is very new because
DRI didn�'t support more than one card before.

Helge Hafting