26 Jul
2019
26 Jul
'19
12:53 p.m.
On Fri, 26 Jul 2019, Jules Richardson via cctalk wrote:
Someone on one of the Facebook vintage groups found an
IBM 5160 with an MDA
display for sale in Australia, except that it's a bit odd in that the machine
had what appears to be an MDA card, the output of which is then connected via
a short external cable to the input on another card, and then an output that
card is what's actually hooked up to the monitor.
The only internal photo of the machine is very poor, unfortunately. I'm
reasonably confident that the "first" card in the "mystery" chain is
MDA,
it's full-length and alongside the DE-shell video output has the usual DB-25
for parallel. The "mystery" card is also full-length, and there's another
full-length card immediately adjacent to it with no external connectors -
that one could easily be RAM, or the hard disk controller etc. but I suppose
it's possible that the mystery item is actually a two-card set.
Anyway, any guesses as to what it might be? The implication is that the
mystery card adds functionality to the MDA card (reminiscent of 3DFX boards
years later), but of course is operating within the confines of what the MDA
display's capable of.
Genlock?
MOST video add-ons were combined onto a board with their own video card,
rather than connecting to IBM's
Co-processor?
Diamond Computer Trackstar was an Apple2 on an ISA card.
It was even sold [briefly] by Radio Shack.
Quadram Quadlink was an Apple2 on an ISA card. The college bought
20 of them. 14 were DOA. 8 of the replacements ("THESE ones are
thoroughly tested") were also DOA. One had a connector (right angle dual
row?) mounted backwards, and could not be connected for testing.
But, MDA (or MDP as described) seems less likely. "Who would want to do
Visicalc or word processing without COLOR??" There did exist a few
after-market CGA cards that had DE9 and DB25 (printer).
Was it in working order? Or had somebody merely cabled the MDA video to a
DE9 serial port? And 5151 will physically connect to CGA (and not work)
We had a couple of "instructors" at the college who didn't see anything
wrong with connecting any cables that fit, including swapping bus mouse
and video, or wanting gender changers to try to connect a parallel
printer to a 25 pin serial port ormodem to printer port. It is
frustrating to try to deal with some people.