On Wed, May 28, 2008 at 11:34 AM, Digby Tarvin <[EMAIL PROTECTED]> wrote: > > I am interested in connecting more than one graphics adapter so that > one can be dedicated to low level diagnostics (rather than the more > usual dual head user interface).. but I am not sure how the hardware > deals with that given that the VGA standard seems to imply that all > the cards would be using identical memory addresses and IO ports.
There are Rules such that only one terminal gets to own the "legacy" ports. > Otherwise I would expect PCI to be able to automatically > map resources to non-conflicting addresses/IO ports. They do. It's just the legacy stuff that gets weird. > > In any case my BIOS has a setting which allows selection between AGP and > PCI as 'primary' Video, suggesting that it is indeed possible to have at > least one of each. it is. > > The only thing I can think of is that perhaps the VGA/CGA/EGA etc modes > are suppressed in the non-primary card, leaving only the more advanced > and less standard mode available. But this would be less ideal, as text > mode would be more useful for low overhead diagnostics. if you can convince the OS to use the non-legacy addresses, you could configure BIOS to put your desired debug terminal at legacy addresses and use it for debug. ron
