Very Computer

by **Loren C** » Thu, 21 Aug 1997 04:00:00

is it possible/practical to run two displays under X?

my thinking is that two 15" monitors would be a reasonable alternative
to a 17 or 19 inch display.

someone told me that the :0.0 in the display variable refers to the
first display and that people do use more than one display and the real
estate is "contiguous". i.e., your mouse moves across the screens and
one window can appear across all screens.

who has done this or seen this? how was the 2nd video card configured,
and what memory address was assigned?

it seems impossible for this to be practical, it seems like people
would be talking about if it was. maybe no one has really thought
about doing it, it would sure be inexpensive compared to a large
monitor. cheap used/new video cards would do fine for a 15"
display.

thanks,

loren

by **Tom Klud** » Fri, 22 Aug 1997 04:00:00

> : is it possible/practical to run two displays under X?

> ...

> : who has done this or seen this? how was the 2nd video card configured,
> : and what memory address was assigned?

> HP of course! ;-)

And Sun, and SGI, and even Linux :)

The biggest caveats:

- XFree doesn't support it. Not likely to support it anytime soon
either. Vendors' X's do. For Linux, look at Metro X.

- Most PC video cards are stupid. Watch out which one you get for the
second display. The only one that I know for certain is supported is
the Matrox Millenium. Check Metro X's homepage for compatible cards.
The second card must have a linear addressing mode, and be able to
disable its VGA memory.

by **Jost Boekemei** » Sat, 23 Aug 1997 04:00:00

Quote:> is it possible/practical to run two displays under X?

> my thinking is that two 15" monitors would be a reasonable alternative
> to a 17 or 19 inch display.

> someone told me that the :0.0 in the display variable refers to the
> first display and that people do use more than one display and the real

This is wrong. :0.0 refers to the first SCREEN of display 0. The next
screen would be :0.1 and so on.

Quote:> estate is "contiguous". i.e., your mouse moves across the screens and
> one window can appear across all screens.

Not possible under X11 and possibly never will be.

However on SPARC Linux you can use XSun which supports more than one screen
per display.
If the mouse leaves one screen, the X-Server re-programs the video-card and
switches to the other screen. Once created, however, you cant move a window
from one screen to another, since the other screen may have a different
geometry (color depth, visual etc.).

You cant use multiple screens on Xfree86 at all, but Xi Graphics
offers an extension to AccelX that supports more than one screen (and
graphic card) at a time.

by **Jost Boekemei** » Wed, 27 Aug 1997 04:00:00

Quote:> Xsun supports multiple screens on SunOS, Solaris ...

Of course. But Loren asked his question in comp.os.linux.misc, so I thought
the question where linux specific.

Quote:> You cant use multiple screens on Xfree86 at all...
>> Not entirely true -- you can use both an SVGA and a Herc monochrome card
>> with XFree86.

Hmm. How do you start Xfree so that the SVGA card shows screen 0 and
the Hercules card shows screen 1 of a given display?

Jost

Quote:> --
> Kaleb S. KEITHLEY

by **Gerin** » Tue, 02 Sep 1997 04:00:00

> > is it possible/practical to run two displays under X?

...

> This is wrong. :0.0 refers to the first SCREEN of display 0. The next
> screen would be :0.1 and so on.

> > estate is "contiguous". i.e., your mouse moves across the screens and
> > one window can appear across all screens.

> Not possible under X11 and possibly never will be.

...
X-Software sells a product named X/bigX. It is a virtual X server which
can connect to multiple screens and multiple x servers! But there are
2 problems:
It is not free and not available for Linux. But perhaps the port it to
Linux if enough people are asking for it (perhaps a "light" version).

With X/bigX you can move windows from one screen/display to another,
because it is only one (virtuall) root window.
--
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Information Systems 61 (frueher/former: GSSE)
Neue Strasse 20, D-38100 Braunschweig
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by **Mick McKin** » Wed, 03 Sep 1997 04:00:00

> >is it possible/practical to run two displays under X?

> Yes, X was designed from the beginning to support this. Sun has in
> the past sold dual-headed boxes.

> >my thinking is that two 15" monitors would be a reasonable alternative
> >to a 17 or 19 inch display.

> Well, maybe.

> >someone told me that the :0.0 in the display variable refers to the
> >first display
> >who has done this or seen this? how was the 2nd video card configured,
> >and what memory address was assigned?

You can get Metro-X on the 'official' Redhat CD (or from Metrolink for
$99). It supports multi-headed displays with the right hardware.
Matrox Millenium's (original, not Mill 2's) have a VGA disable switch
that you can use to turn off the VGA signals at boot and let another
card be the "console" the system sees at boot time.

I have used this with an old plain-vanilla ISA vga card and a newer PCI
Cirrus Logic card with good results. The problem is that cards with
less hardware support for windowing features (hardware cursor, blitting,
etc...) will use up more CPU time than the Millenium, so when windows on
the 'lesser' card are in focus, CPU usage goes way up. I noticed that
in xosview the idle cpu time appeared to be around 99% when a Millenium
window was in focus, and well into the 20%-30% range when the other
display is in focus.

I guess the solution (now that prices are dropping) is to get a couple
(or more!!) of Millenium 1's and jumper 1 as VGA and the other as no-VGA
and rock on!!

(Xi offers multi-head support with AcceleratedX, but it is an add-on
that brings the total cost to about $150 just for the X server and
multi-head feature)

--
Mark McCoy

by **Joe Bu** » Thu, 04 Sep 1997 04:00:00

>is it possible/practical to run two displays under X?

Yes, X was designed from the beginning to support this. Sun has in
the past sold dual-headed boxes.

Quote:>my thinking is that two 15" monitors would be a reasonable alternative
>to a 17 or 19 inch display.

Well, maybe.

Quote:>someone told me that the :0.0 in the display variable refers to the
>first display

the DISPLAY variable is hostname:displaynumber.screennumber .
From the Solaris X manpage (I'm not sitting in front of a Linux
box now, but it is the same):

displaynumber
The phrase "display" is usually used to refer to
collection of monitors that share a common keyboard
and pointer (mouse, tablet, etc.). Most worksta-
tions tend to only have one keyboard, and therefore,
only one display. Larger, multi-user systems, how-
ever, will frequently have several displays so that
more than one person can be doing graphics work at
once. To avoid confusion, each display on a machine
is assigned a display number (beginning at 0) when
the X server for that display is started. The
display number must always be given in a display
name.
screennumber
Some displays share a single keyboard and pointer
among two or more monitors. Since each monitor has
its own set of windows, each screen is assigned a
screen number (beginning at 0) when the X server for
that display is started. If the screen number is
not given, then screen 0 will be used.

Quote:>who has done this or seen this? how was the 2nd video card configured,
>and what memory address was assigned?

You need two things: underlying support at the OS level for multiple
screens, and an X server on top of this that knows how to talk to it.
I think some of the commercial X servers support multiple screens.

There have been "dualmon" patches for earlier versions of Linux, but
I don't know if that code is currently supported. The original version
would work with a Hercules-compatible card plus a VGA-compatible one
(you needed the two different kinds of cards because their addresses
would overlap otherwise).
--
-- Joe Buck http://www.synopsys.com/pubs/research/people/jbuck.html

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by **Tom Klud** » Fri, 05 Sep 1997 04:00:00

> A nifty solution I came up with that works for PCI graphics cards is to just
> write to the config registers of the cards. PCI register 4 contains the i/o
> enable and memory enable bits. If you turn those off in one board and on in
> another then the first board will no longer respond to i/o memory accesses,
> while the second one will.

> Even though a card may be disabled, it is still refreshing the display. This
> lets you use the same addresses for both cards (since PCI config space is
> unique for each device), provided you have a little program or added code
> that does the enable/disable for each PCI device.

Sounds good, now where do I get an X server that does this? :)

BTW, I have an ATI PC2TV and a Cirrus Logic 5434 (both PCI). Under
Memphis (Windows 97), I can have both installed and working, with the
5434 being the second display. I would be very interested in any
products for Linux which would allow me to do the same.. (All the
dual-head Xservers for Linux that I am aware of require the second card
to be a Matrox)

Perhaps GGI? I seem to remember it supporting multi-head displays..

by **Kaleb S. KEITHLE** » Fri, 05 Sep 1997 04:00:00

> > Even though a card may be disabled, it is still refreshing the display. This
> > lets you use the same addresses for both cards (since PCI config space is
> > unique for each device), provided you have a little program or added code
> > that does the enable/disable for each PCI device.

> Sounds good, now where do I get an X server that does this? :)

> BTW, I have an ATI PC2TV and a Cirrus Logic 5434 (both PCI). Under
> Memphis (Windows 97), I can have both installed and working, with the
> 5434 being the second display.

Yes, and two years ago Bill Gates tried to tell us that they (Microsoft)
invented long file names too.

Quote:> I would be very interested in any
> products for Linux which would allow me to do the same..

X, as a protocol, has supported multiple screens since day one, i.e.
1987. Implementations vary, but most Unix workstation have supported
multiple screens for years. Your choice of Intel/ISA/SVGA hardware is
the limiting factor in being able to do multiple screens, and I don't
think it's the least bit surprising that support for multiple screens on
the newer PCI hardware in the low volume Unix-on-a-PC world lags behind
Microsoft, which as a company has infinitely more resources to throw at
the problem.

That not withstanding, I believe that both Metrolink and XiGraphics have
multi-screen servers for Wintel PCs. Whether they have one for your OS
and your graphics card is a question that perhaps only they can answer.

--

Kaleb S. KEITHLEY

by **Mark Vojkovi** » Wed, 10 Sep 1997 04:00:00

>> A nifty solution I came up with that works for PCI graphics cards is to just
>> write to the config registers of the cards. PCI register 4 contains the i/o
>> enable and memory enable bits. If you turn those off in one board and on in
>> another then the first board will no longer respond to i/o memory accesses,
>> while the second one will.

>> Even though a card may be disabled, it is still refreshing the display. This
>> lets you use the same addresses for both cards (since PCI config space is
>> unique for each device), provided you have a little program or added code
>> that does the enable/disable for each PCI device.

>Sounds good, now where do I get an X server that does this? :)

>BTW, I have an ATI PC2TV and a Cirrus Logic 5434 (both PCI). Under
>Memphis (Windows 97), I can have both installed and working, with the
>5434 being the second display. I would be very interested in any
>products for Linux which would allow me to do the same.. (All the
>dual-head Xservers for Linux that I am aware of require the second card
>to be a Matrox)

I'm not sure that metrolink's server requires that both be
Millenniums (www.metrolink.com).

It's also on the wishlist for XFree 4.0.

Mark.

by **Yrj?n? Rankk** » Sat, 13 Sep 1997 04:00:00

* snip snip *

Quote:> > I would be very interested in any
> > products for Linux which would allow me to do the same..

* more stuff deleted *

Quote:> That not withstanding, I believe that both Metrolink and XiGraphics have
> multi-screen servers for Wintel PCs. Whether they have one for your OS
> and your graphics card is a question that perhaps only they can answer.

I've got 2 MGA/MIL's under the hood and tried out MetroLink's server. Everything
else worked fine, but I had some weird problems with the cursor and screen updating
in xemacs. Seems like the anomalies were caused by the two displays, because
everything was cool with the second display disabled.

Had to ditch it then. Didn't have the time to dig into the problem seriously...

Anyone having had similar experience? What about Xi's server?

Quote:> --

> Kaleb S. KEITHLEY

-- Yrj?n? Rankka

Very Computer

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)

two X displays, two video cards (?)