Re: Identify this card?

[et472@FreeNet.Carleton.CA (Michael Black)]

Leon Howell (puritan_2076@yahoo.com) writes:
>> Good read... 6845's are used in all kinds of wacky early 80's 
>> PCBs (including arcade games),
> 
> Huh? Arcade games?  I don't remember any B&W arcade games. Are you
> implying that this chip is capable of color? If so, *Thousands* of
> Apple & non-Apple users might be interested in a hardware hack! :)

You just parallel some more bits of memory, to add some bits to control
color.  The same way that there was an option on the OSI Superboard II.

What you miss is that the 6845 is a fairly generic device.  It required
quite a bit of extra circuitry in order to work (witness the comment
about using it with dynamic ram), but that means it was very flexible
in its applications.  One might really look at it as a RAM controller
for video applications.  You needed an external character generator ROM,
you needed the rest of the video circuitry after that, and it was fairly
programmable, and hence there was no problem doing other things with it.

Had it been one of the later 80-column ICs, there would have been severe
limitations.  Those provided for much more compact operation, but there
wasn't much you could do but build it up as the manufacturer showed in
the application note, feed in your characters at one end and get video out
the other.

There were plenty of applications that used the 6845 for color, back
when the Apple II was current.  And maybe a lot more after that, when
it was used in the IBM CGA card, and later iterations of IBM video (unless
by that time it was integrated into other circuitry, and the 6845 core
was a subset of what was there).

    Michael