22 May
2006
22 May
'06
5:43 p.m.
On 5/8/2006 at 2:32 PM Chris M wrote:
I just received the first part of a shipment which
includes an IBM 5175 monitor. The PGA card and
possibly the AT box it resides in is on it's way. I
plugged the monitor into my Vermont Microsystems card
(essentially a PGA clone), and it worked like a charm.
Have yet to plug the monitor into a VGA card and
investigate that noise (the PGA card possibly has some
funky syncing scheme, like combined sync or
sync-on-green). But regardless, I'm desirous of docs
for these babies, technical or otherwise. Programming
infor-mation is of the utmost importance. Can anyone
help?
First off, you need to understand that the PGC was a bizarre creature,
unlike any other display adapter that IBM made. Because of this, there's
darned little software that's going to be able to use it in anything other
than CGA emulation mode.
To start with, the display in PGC native mode isn't memory-mapped. You
pass the 8088 onboard CPU drawing commands and it interprets them. Because
of this, the drawing speed of the PGC isn't terribly high and a PC AT with
an EGA can easily outdraw a PGC.
IIRC, the PGC, was power-hungry, took 3 cards and 2 slots(!) and very
expensive--and introduced not long before the PC AT, so it became an orphan
pretty quickly. Compared with the EGA, the PGC does offer a 256 color
display out of a 4096 color palette--but the VGA improved on this
considerably and pretty much rendered the PGC a dead duck. According to
the website below, there were clones from Matrox, Vermont Microsystems,
Orchid and Everex, although I can't recall seeing any of them.
At any rate, rather than scan the very long Techref, here's some useful
informaton. The first is from IBM that documents the whole idea behind the
thing:
http://www.research.ibm.com/journal/sj/241/ibmsj2401D.pdf
Here's information about programming:
http://www.seasip.info/VintagePC/pgc.html
Cheers,
Chuck
P.S. Is anyone else getting these messages more than a week after they were
sent?