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
