Re: melting through 2901s?

Clay Cowgill wrote:

> >I was wondering if an Atari mathbox could be emulated on a sufficiently
> >fast
> >micro-controller, since the AMD 2901s are going to become scarcer and
> >scarcer.
> >I'm pretty sure it could be done.
>
> I'd thought about that too-- in particular, Jeff and I had discussed adding
> a little "mathbox"-like board to Space Duel to use it as a general-purpose
> development platform for new games. (Seems like Space Duel is one of the
> more common vector games out there, and it has lots of buttons. ;-)
>
> I was quite pleased with the number of "math-co-ops" that a 100MHz Scenix
> processor could do just running the reference Microchip PIC math libraries.
> I don't really know what kind of speed the Atari Mathbox achieves though.
> Those 2901's are pretty fast.
>

2901's aren't very fast compared with modern chips. Back in their day they were
used when a general purpose processor couldn't hack it, or a VERY strange
instruction set was needed. My only non-game meeting with them was using
something like a 64-bit wide instruction word where part of the word was data
source, part was where the data should go, part was what the 2901 should do with
the data, part was the SPEED of that cycle, part was for program jumping, etc.
There was actually a chip made that would allow you to change the clock speed to
any of 8 different speeds PER CYCLE. Some things (like shifts) could be done at
full speed, others (like pick an off-chip source, do math on it, and send to an
off-chip destination) could end up being relatively slow.

The ideal chip to use for a mathbox these days would be something like the
TMS32050. It could handle anything you could throw at it and (thanks to little
tricks like being able to shift, add, and multiply in almost any combination,
most times in a single cycle!) could do some very nifty scaling.

Somewhere I have some drop-in replacements for the 2901's that were done in
CMOS. Possibly IDT made them. I wonder what I ever did with them. There were
even CMOS replacements for the 2916 that could have replaced all 4 of the 2901s
using a single chip. I don't think I ever had any of those, though.

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Received on Mon Feb 12 04:57:37 2001