IBM 5160 with oddball MDA input/output card

[Jules Richardson]

On 7/26/19 9:50 AM, Tony Duell wrote:
> Are you sure it's MDA rather than CGA. The reason I ask is that I have a
> full-length 8-bit ISA card in my collection that connects between the CGA
> card and its monitor (it also provides a composite video output if you want
> that) _and_ inside the machine it connects between the floppy controller and
> the drives.

Hi Tony,

The person who was asking about it said that it's a 5151 display, although 
I've not seen any photos showing the front of the machine/monitor, so I 
can't be 100% certain. Having said that, the lower part of the monitor's 
back is visible in one photo, and it has captive power + video cables off 
to the left and no controls, which seems consistent with a 5151; I believe 
that the 5153 and 5154 had a power socket and brightness/contrast controls 
on them.
> 
> There's a 6502 processor on said card and it claims to provide an emulation
> of the Apple ][

That's an interesting beast. I did wonder if this was something along those 
lines, too, i.e. a non-x86 processor card for the purposes of emulating 
something else - but the only one I'm aware of is the XT/370, and I don't 
believe that did any kind of video pass-through (that and I think it was a 
three-board set, where this is two at most).

> If yours is MDA then I wonder if it's some graphics add-on (remember
> the original
> MDA was text only). But most of those, like the Hercules, provided the text mode
> as well and were stand-alone cards. It wasn't much extra logic to do that.

Indeed. Whatever it is still appears to run within the limits of the MDA 
display, so it's not color, and resolution-wise it must be more or less in 
line with Hercules. As you say, there wasn't a massive increase in logic 
when comparing Hercules to MDA, so it seems odd for a card to exist which 
still required an MDA adapter to be present; I feel there's got to be some 
additional functionality being offered, too.

cheers,

Jules