CGA card (Mitsubishi Electric) with 192K RAM?
jules.richardson99 at gmail.com
Sun Sep 6 15:27:32 CDT 2020
Digging through old PCs, on a battery-removal spree... came across a Sperry
3070 XT-a-like (I wouldn't quite call it a clone, it's a bit goofy) which
has a Mitsubishi Electric system board, RAM expansion, and video hardware.
The video hardware is... odd. It's actually two full-length boards, joined
with a large IDC cable along the top edge as well as via the ISA bus. The
only "complex" IC is a 6845 - other than that it's masses of TTL.
Output is via a DE9, and pinouts seem consistent with CGA (15.7KHz on pin
8, 60Hz on pin 9, 3/4/5 at TTL levels and 1/2 ground). There's also an RCA
jack on the backplate, and that 6845 IC... it all seems very CGA-like,
except that total video memory is 192KB.
CGA was normally 16KB, I believe. Hercules and EGA 64KB, although I think
toward the end of EGA's existence there was a 192KB option. Physical
outputs aren't consistent with EGA's two bits per pixel, though.
Does this ring any bells with anyone? I don't know why it needs such a
large amount of RAM if it's stuck with CGA capabilities. One board is
branded WECD10 and the other WECD11, but there's no "model" or anything.
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