The near-mythical IBM color MDA

[Chuck Guzis]

On 08/23/2018 08:31 PM, Eric Schlaepfer via cctalk wrote:
> I'm not that lucky! But yes, an early card with the light pen connector
> should work.
> 
> The card I used for the demo is a somewhat later revision. I added rework
> wires to match the schematic in the technical reference manual of the
> earlier revision.

I had the original MDA and a rather ancient light pen from some graphics
console or another.  I hooked it up to a 6-pin Berg header and got it to
work, sort of.  I didn't use the interrupt 10h BIOS functions, though,
but rather accessed the 6845 registers directly.

The operation was pretty terrible.  The medium-long persistence of the
monochrome monitor led to large positioning errors.

I recently sent the pen to Glitch, who hasn't gotten back to me to
report wether it still works.  It was pretty nice with a
pressure-activated tip swich with fiber optics coupled to a
phototransistor, with a couple of transistors to boost the signal.

Black with a coiled cord--6 conductors, I think.


--Chuck