30 Sep
2002
30 Sep
'02
2:50 p.m.
An RCA CDP 1801 CPU board,
[...]
This is a 4.25 inch by 2.75 inch (including fingers)
blue-colored PCB
with a 40-pin CDP1801UD data path chip and its
associated 28-pin SSTC TA6890W control store ROM, along with some
passive support components.
Quite a find!
According to documentation I've seen, the original chip set was the TA6889
and TA6890. The later ones are CDP1801R and CDP1801U. I'm not sure whether
there were actual differences in the chips, or whether they just changed the
part numbers.
I've only seen a reference to one other RCA chip with a TAxxxx part number,
and it was a CMOS RAM. I suspect that the "TA" prefix may have been used
for preproduction (non-qualified) parts, similar to the Motorola "XC"
prefix.
The TA68xx/CDP1801 supports only a subset of the instructions of the 1802.
The instructions that were added on the 1802 were quite commonly used,
so don't count on it running 1802 software.