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SubjectRe: CHALLENGE!!! =)
On Thu, 13 Aug 1998, David Schleef wrote:

> >
> > On Wed, 12 Aug 1998, root wrote:
> >
> > > Hi everybody!!!
> > >
> > > This is a challenge for me ... and those who don't know how to
> > > do it. =) How can I plug in a second SCREEN on a second VIDEO CARD in linux?
> > >
> > > I mean : I have a 15" SVGA Screen which I use in X-windows, and I would like
> > > to plugin a 14" VGA Screen on a second video card....
> > >
> > > Do you know that?
> > >
> > > if yes, reply here and at KURDT@VIDEOTRON.CA
> >
> > Sure! It's easy!
> >
> > 1) Turn off computer
> > 2) Open up your computer
> > 3) Find a free bus slot for your second video card.
> > 4) Plug the card into that slot.
> > 5) Put the case back on the computer.
> > 6) Plug the second monitor into the second video card on the back
> > of the computer.
> > 7) Plug the power cord for the monitor into the wall outlet.
> >
> >
> > Piece of cake.
> >
>
> And this could potentially blow up both video cards, since they don't
> typically have protection against two cards driving the bus at the
> same time. (The Diamond Speedstar in my hand appears to use 74LS245's
> to tristate the data lines, but if you connect the output of one to
> the output of another when neither are tri-stated -- blammo!)

Plug 'n Play compliant hardware is supposed to be immune to this.
Lots of ostensibly PnP cards don't meet the spec in various ways, however
|-<. I haven't heard of this causing a problem, but that doesn't mean it
can't (or hasn't) happen(ed).

> There are various web pages and FAQs discussing this. I have no references,
> since it is just as easy for interested people to search for these as it is
> for me.
>
> The cases where you could potentially use two video cards (hardware limitation):
>
> 1 Both are on the PCI bus

And can be MMIO relocated correctly - bugs abound. Conflict
matricies of card-card multihead interactions will need to be written up,
and probably codified in KGI as well. Yes, there are that many special
cases to consider.

> 2 One is on PCI and one is VGA on ISA (maybe)
> 3 VGA and MDA
> 4 You have a modified VGA card that translates bus addresses

5 One VLB and one ISA/PCI.

> Assuming you have such a combination ready, you must look for software that
> can handle it. There is a commercial X server that handles multi-heading for
> the PCI/PCI case. I've heard reports of people using MDA as a console and
> VGA for X. Last I checked, there did not appear to be kernel support for
> multiple consoles. (sounds like a fun project...)

KGI can multihead VGA/MDA, VGA/PCI and PCI/PCI. Only a few cases
have been tested, but it does work.

Jon

---
'Cloning and the reprogramming of DNA is the first serious step in
becoming one with God.'
- Scientist G. Richard Seed

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