IBM 5160 with oddball MDA input/output card

[Fred Cisin]

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.