multiple CGA cards on ISA bus?

[Fred Cisin]

On Sat, 23 Dec 2006, Richard wrote:
> Does anyone know if its possible to have multiple CGA cards on an ISA
> bus?  I have a feeling the answer is no...

You're right, but they can be modified

> If the answer is no, can anyone recommend a good set of docs on the
> bus interface of a CGA (memory mapped regions, relevant BIOS vectors,
> ISA bus transactions, etc.)?

PC, XT, or AT Technical reference manual
It has schematics, and source code for the BIOS.

You'll need to change the address of the Video RAM (currently at B800, but
A000 to b800 is available, unless you also have MDA, EGA, or VGA in the
machine), and the ports for the board.

> I have a project where I want to gang drive a group of CGA displays.
> Initially my thoughts were to just have N computers with CGA cards and
> gang drive the computers over a serial port.

comparable price, and less work, more bulk