For those not faint at heart ......................
I've got 4 * AMD2903 + 1*AMD2910+1*TRW1010 (Muliplier-CHIP)
And a few fancy Motorola synchronic "uart's" (MC2652L2)
For the price of $0,00 + Postage & handling (from the Netherlands) +
Pictures of the brewing results
Sipke de Wal
chances are very slim I'll ever get to them myself......
----- Original Message -----
From: Tony Duell <ard(a)p850ug1.demon.co.uk>
Sent: Sunday, February 27, 2000 10:38 PM
Subject: Re: Am2901 sbc, WAS: A classic classiccmp day...
> > From: Tony Duell <ard(a)p850ug1.demon.co.uk>
> <> >Any other AM29xx chips on it, like a 2909 or 2910 sequencer? Or is
> <> >just a demo board for a 4-bit ALU
> <> >
> <> >It sounds like a really interesting find, though. The 29xx series
> <> >were interesting devices that have
been used in all sorts of
> <> Yep, there is a 2909 on board too....
> <Ah, so there's a sequencer. And presumably, therefore, there's some
store (ROM or RAM) on the output of that. So it sounds like
<it's a complete processor, albeit a small one.
How small depends on the microcode. It could easily be PDP8 or Nova
He said _a_ 2909. That implies a 4 bit microcode address, which limits it
to 16 locations. 16 micorocode words and a 4 bit ALU is a small processor
IMHO. And being an AMD design they won't have simply concatenated an
'instruction' from external memory (which this board probably doesn't
have anyway) with those 4 bits.
For people who've not come across the AMD sequencer chips, they're quite
nice, and even have things like a return stack (about 4 levels IIRC) to
allow for subroutines in the microcode.
The 2909 and 2911 are very similar. They provide a 4 bit 'slice' of the
microcode address logic -- program counter, subroutine stack, etc. You
can cascade them to make as wide an address as you like. The difference
between these 2 chips is minor -- IIRC, one of them has separate pins for
inputs that are combined on the other one, and also has inputs that are
ORed with the address output.
The 2910 is essentially 3 2909s together with some glue logic in a single
chip. If you only need 4K of control store it's a nice chip _but it can't
be extended to give more bits without kludging_. Three rivers made that
mistake on the PERQ -- the first PERQ had 4K of control store and used a
2910, all later models had 16K and used a 2910 and a '2 bit kludge' (pun