15 Mar
1999
15 Mar
'99
9:16 a.m.
The light pen was generally asociated with the video card until EGA came along.
Most dropped the light pen connector. One of the "multifunctions" of the 6 was
real time clock. AST's SixPak has added memory, RTC, 2 serial ports (one is
socketed for optional UART and driver chips), parallel and joystick (I think
joytick, my brain hurts today).
Tony Duell wrote:
> >
IBM's braindead decision to have 5 (instead of 8) expansion slots meant
> > that aftermarket "multifunction" cards became quite popular. MANY
of
> > them advertised SIX functions; after memory, serial, parallel, and
> > joystick, how many people remember what purported to be the other two
> > functions?
[...]
Wasn't it a light-pen ? Or is that covered
under serial ?
I would be _very_ suprised if that was the case. The easiest way to
implement a light pen is to use the signal from the light pen sensor to
latch the current video refresh address on the video card. The 6845 chip
(used on the CGA nad MDA cards) has an input just for this. And on both
of those cards that input is wired to a little header plug, to connect to
a light pen.
Trying to build a lightpen on anything other than a video card would seem
to be insane...
ciao larry
lwalker(a)interlog.com
-tony