Re: dual head video system

[Floyd L. Davidson]

ken <gebser@speakeasy.net> wrote:
>Floyd L. Davidson wrote:
>
>>(For anyone that hasn't tried it, using a dual head video system
>>under X is just astounding!)
>>
>>
>That tasty morsel has had me salivating for a long time.  How do
>you do it?  Is there a webpage or two which is/are particularly
>helpful?

Start by using google to find this Message-ID
87isb4afo3.fld@barrow.com, which is a description of XFree86
configuration that was posted to comp.os.linux.x last August.

Then search the web and Usenet archives for "xinerama" and
you'll find more about the mechanism.  If you have one
particular video card in mind, add a keyword for that too.

Basically it requires either two video cards or a video card
that supports dual monitors.  Neither the cards nor the monitors
need to be identical.  A number of inexpensive video cards
support dual monitors, so it does not require high end hardware.

I fired up one box using an old PII-300mHz and two old video
cards with 4K of RAM each, plus two 15" 1024x768 monitors that I
picked up at a local "surplus sale" for $10 each.  It is a
Point-Of-Sale system now...  In fact, that project was what got
me to try it, as I bought the old PII box with a 17" monitor for
peanuts just for the POS system.  But when I saw xinerama in
operation, that 17" monitor was quickly relocated to my work
position, as the existing workstation already had a G400 Matrox
video card.

But what it does is what you really want to know about... :-)

The two monitors can be totally separate, or they can be
combined as if they are one big screen.  They can also be at
different resolutions, though that gets strange if they are
combined.  With a combined screen, the second monitor's screen
can be positioned anywhere relative to the first.  They can be
stacked vertically or horizontally, with position 0,0 being
either the top, bottom, right or left monitor.

The only limitations that I discovered were having to use
builtin VESA modelines as I could not get mine to work with a
custom screen resolution, plus if your X server is configured to
switch between screen resolutions, only the first screen can be
switched.  One external problem is that so far not many programs
are xinerama aware, so such things as popup windows from your
web browser might just land smack in the middle of the extended
screen...  half on one monitor and half on the other. That's a
bummer, but not hard to ignore.  Eventually we can expect all
programs to check for dual monitors and adjust appropriately.

-- 
Floyd L. Davidson           <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska)                         floyd@barrow.com