29 Dec
2012
29 Dec
'12
5:29 p.m.
On 28 Dec 2012 20:02:21 Chuck wrote:
Maybe I've got the name wrong--perhaps it was
called the EDB--it was a
display enhancement board added to the M24 and attached to the standard
controller that provided 16 colors per pixel (IIRC) in 640x400 hi-res mode.
I see, I think you mean the EGC (Enhanced Graphic Color board). I never had an EGC board
but I have the user guide of it. The board adds three bit planes to the one of the
Indigeneous Card (IND), so it provides 16 color capability to the higher screen
resolutions and it adds the flexibility of a color/shades of grey Look-Up Table (LUT)
The video bit planes are laid out as folows:
A0000h-A7FFFh Bit plane 0 (EGC)
A8000h-AFFFFh Bit plane 1 (EGC)
B0000h-B7FFFh Bit plane 2 (EGC)
B8000h-BFFFFh Bit plane 3 (IND)
The MDA card has the following memory layout:
4k of RAM at address 0B0000h for its display buffer.
This address is not completely decoded;
the entire 32k from 0B0000h to 0B7FFFh is filled with repeats of this 4k area.
I/O addresses 03B0h-03BFh.
As you see the memory of Bit Plane 1 overlays that of the MDA card completely. So I think
it will cause serious problems.
Are you familiar with the card? Do you have one?
Greetings, Hendrik