> > So, as I already said, I think some kind of serialization of video
> > device accesses is needed between the multiple X servers.
>
> So who would be qualified to attempt such a thing?
> Who do we have to beg ? :)

Well, I'm still hoping that perhaps some XFree Xpert (this is the
right mailing list, isn't it?) will either confirm or refute my
assumptions about the inner working of XFree VGA device access, and
ideally even provide some advice. Then, I'm willing (and eager) to
have a try at this mighty task...

> >>   I saw a demo of Linux + XFree86 4.1.0
> >>   with 4 DISPLAY( Mon,KB, mouse).
> >>
> >>   All USB KBs are connected to a MiniUSB Hub and Hub is
> >>   connected to machine, And USB mouses also connected in
> >>   similar way.
> >
> >Yeah, I have that working too. But next time you see it, try
> >switching to a console, or running a DGA app... and then run fast.
> >:-)))
>
> so how does this work?  Or will it crash randomly?

I think I already wrote this, but anyway: I use the patch from
http://cambuca.ldhs.cetuc.puc-rio.br/multiuser/ with XFree 4.1.0. (I
tried 4.2.0 but the USB keyboard doesn't work, and there's no visible
improvement in stability or anything.) I've modified the patch to
avoid disabling not only pci I/O accesses but also memory accesses.
With this config, I can run four X servers, each using one nVidia,
one keyboard and one mouse. This works with the closed-source drivers
from nVidia, when BIOS-driven card initialization is disabled (the
default). When you enable BIOS (interrupt 10h) in the nVidia driver
options, or when you use the open-source nVidia driver that is
included in XFree, or when you use for example ATI cards, S3 cards
etc., the computer hangs totally at the moment you start the second X
server. (Also reported working are Matrox cards, but I have no
personal experience with them.) Even in the working configuration,
though, you can't use Ctrl+Alt+Fn to switch to the console, and you
can't make VMWARE run in full-screen mode (unless the VM's resolution
is the same as XFree's). When you try that, the computer hangs
completely. Otherwise, it seems stable. Might be usable for home when
you are aware of the limitations, but not for offices, public places
etc.

As to the VMWARE full-screen problem - I am not completely sure here,
but is it using the DGA extension or what? Because normal mode
switching with Ctrl+Alt+plus/minus works (i.e. does NOT hang the
machine), so VMWARE must do it somehow differently...

Vaclav Dvorak   [EMAIL PROTECTED]
IDAS, s.r.o.    http://www.idas.cz
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