25 Jan
2004
25 Jan
'04
2:23 p.m.
On Sun, 25 Jan 2004, Tom Jennings wrote:
I AM NO EXPERT on this, but I'd like to point out
that the meaning of
"compatible" was far more slippery then than now. AFAIK the Phoenix BIOS
was the first true compatible (eg. the number of incompatibilities was
very, very small). The early Compaq machines were considered
"compatible" even though they did not have 100% ROM compatibility, and
the video interface was different. A lot of software in '82 - '84 used
things like int 10h to talk video to 25x80 mono screens, don't forget...
and that's trivial to do (eg. on my Multibuss/TVI-950 MSDOS 3 machine!)
I agree that NOTHING was 100% compatible!
But, I don't understand what your point is,...
The usual video for the Compaq portables was CGA (connected
with a mid-board connector to the internal B&W monitor)
IIRC, it responded pretty much identically to the IBM CGA,
in terms of INT10h, and to direct video writes to segment B800h.
In what ways was its video interface (except for the extra
internal connector) different?
OTOH, the Corona had some noticeable differences,
such as the character attribute of 78h.
--
Grumpy Ol' Fred cisin(a)xenosoft.com