Re: Two (S)Vga at the same time (PCI System)

Goggles (
Tue, 2 Apr 1996 10:30:11 -0700 (MST)

> In <> Antoine Reid <> says
> > What if we talk about a (s)vga [either isa, vesa or pci] and a mono [isa..]
> > hercules/mda card? Do you think the mono card is init'es at bootup? mine is
> > usable in mess-dos so I guess it is ... (?)
> The IBM planar BIOS will initialize both an MDA and a CGA (if either or
> both are present) as part of the POST. If both are present, which one is
> used for the boot messages is selected by that Color/Mono switch on the
> System Board. Remember that switch? This was what it was for. ;-)
> These initializations occur very early in POST so that errors may be
> reported on the console. EGA and later IBM display schemes (and all 3rd
> party schemes such as SVGA, VESA, &c.) are initialized by adapter ROM
> using the standard IBM mechanism for that which occurs at the very end of
> POST. As a result, these display adapters must do a simple default
> initialization triggered by power in order to be able to display any POST
> error messages from the processor.

I've run VGA and Hercules boards at the same time. In DOS, you can even
use "mode mono" and "mode co80" to switch between the two. So it would
seem they both get initialized, or else the mono card maybe doesn't need
any special attention; maybe it defaults to a working text mode. At any
rate the mono text VRAM doesn't overlap any of the memory space of the VGA
board. So you can put text on the screen by writing to the mono board's
VRAM (which I believe is at C8000 if memory serves). Now, Hercules is
a different story; there is some overlap between part of the graphics
VRAM and the VGA, in some VGA modes. But you can always do mono text
regardless what the VGA is doing.

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