IBM 5160 with oddball MDA input/output card

[Jules Richardson]

On 7/26/19 2:53 PM, Fred Cisin wrote:
> Genlock?
> MOST video add-ons were combined onto a board with their own video card, 
> rather than connecting to IBM's

It seems odd within a 5151/MDA context though - plus the system seems 
entirely self-contained, i.e. not designed to interact with any other video 
equipment.

> 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.

Something like that is certainly sounding plausible to me - not necessarily 
Apple II, but *something* that provides non-x86 processor ability, and 
presumably which involves video output above and beyond MDA (otherwise why 
wouldn't it drive the MDA card directly), and yet still monochrome and 
compatible with a 5151.

> 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).

I did manage to locate the original seller's listing, which didn't really 
provide any new information - but there were a couple of pictures of the 
monitor confirming that it is a 5151.

> Was it in working order?  Or had somebody merely cabled the MDA video to a 
> DE9 serial port?

The thought had crossed my mind, too. Seller's claim was that they had it 
booted to a DOS prompt, then smoke came out of the PSU; if they're honest 
then it's likely age-related demise of RF suppression caps or maybe a 
tantalum somewhere.

I did get the impression that they don't really know what they have, i.e. 
to them it's just an old XT (and therefore worth a small fortune).

The cable connecting the MDA's output to the mystery card does rather look 
like it was made for the purpose - it's conveniently long enough to bridge 
between one or two slots, and the cable appears to exit the connectors at a 
45 degree angle to account for the MDA's output being toward the top of the 
card while the input to the mystery card is toward the bottom.

> 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 suppose that's the only good thing about the modern "everything is USB" 
world... :/

cheers

Jules