"CP/M compatible" vs. "MS-DOS Compatible" machines?

[Chuck Guzis]

> Date: Thu, 31 Jan 2008 23:04:55 +0000 (GMT)
> From: Tony 
 
> IIRC, while the MDA card had a light pen connector, it was never really
> documented or supported by IBM, due to the fact that light pens didn't
> work properly with the very long persisnence phosphor of the 5151 
> monitor. The CGA card's light pen connector was docuemtned, though
> (although I have never seen a light pen designed to work with it

I've got a light pen that was salvaged from some 60's era graphics 
equipment.  This is the kind with the fiber optic tip and a 
microswitch that determines when the tip is depressed.  Has some 
discrete circuitry in it (probably an amplifier, pulse shaper, etc.) 
and works just fine with the MDA/CGA/EGA cards.  About the diameter 
of a felt tip marker (ca. 3/4").  I once used it with a monitor with 
a short-persistance white phosphor.  It wasn't bad; just couldn't 
think of a good application for it.  I've got a VGA card here 
(Paradise I think) that also has the connector, but it's hooked to an 
LCD monitor, so that's not going to work very well--but does give 
another reason to hang onto CRT displays.

Cheers,
Chuck