On 2019-07-26 4:53 p.m., Fred Cisin via cctalk wrote:
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.
I know of a "trained" service technician who inserted an PCI card into a
ISA card slot and then call for assistance because it did not work.
Fix.. swap technician...
Paul.
