Attention 1802 fans...

From: Ross Archer <archer_at_topnow.com>
Date: Mon Sep 30 20:51:00 2002

Eric Smith wrote:
>
> > 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!

I'll say. And a bit of 1802 trivia:

The 1802 was used in quite a number of Amateur radio ("ham")
satellites.
It was one of the first relatively "rad-hard" micros from
what I remember
reading, due in large part to its CMOS construction. I
guess those days
there were a few PMOS CPUs (8008, 8080) and a few NMOS CPUs
(Z80, 6502,
9900JL), and exactly one CMOS CPU -- the CDP1802. So it was
1802 or bust. :)


I don't recall hearing about commercial and military
satellites, but I'm
guessing they also used this chip extensively for a time.

I suppose if e-bay prices go high enough for the chips, you
can always
launch a mission to recover one of those sats for the chip
salvage. ;)

An observation about the 1802.

Most micros' instruction sets I remember from those days
tended to
be either simple and likeable for their elegant minimalism
(6502, 6800),
or were complex and irregular, but likeable because of
really neat
and powerful instructions (Z80 w/CPIR, LDDR, XTHL etc.), or
interesting
for just being plain weird (9900). I remember pegging every
micro of the
day into one of those camps (simple, complex, weird) except
one: 1802.

The 1802 is the only one that seemed to me to be elegant,
simple, and
clean and yet so weird that it must have been the product of
a
completely alien intelligence. Perhaps one that GLOs in the
dark...

No doubt at any rate the 1802 was interesting and unique.
It's great
that folks on the list care more about seeing this rare gear
see use
than fall into disuse as part of a "collection".


>
> 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.

that BLO's. ;)
Received on Mon Sep 30 2002 - 20:51:00 BST