Good haul of old pc stuph

[Tony Duell]

> 
> On Tuesday 20 December 2005 11:45 pm, Jim Leonard wrote:
> > This is an original IBM CGA, not a clone.
> 
> Speaking of such,  what are the RCA jacks (two of them) on those cards for?  
> Is one of those supposed to be a composite output?

The IBM CGA card has one RCA socket (in the UK, we called it a 'phono 
socket', BTW). It is composite NTSC video. Stnadard signal level, etc.

The IBM EGA card has 2 such sockets. Both are essentially unconnected. 
The outers are connected to logic ground, the inners go to pins on the 
'feature connector' only. I actually added a little daughterboard to an 
EGA card years ago (a couple of TTL chips, a few discretes) to make 
composite mono video available on one of the RCA sockets, to drive a 
greenscreen composite monitor. Remember that the EGA card can do US TV 
(==CGA) rates.

-tony