On 10/25/2018 01:40 PM, Paul Koning via cctalk wrote:
On Oct 25, 2018, at 1:45 PM, Chuck Guzis via cctalk <cctalk@classiccmp.org>
wrote:
On this subject, is there no interest in serial ALU designs? At one
time, if you wanted a low-cast implementation, that was the way to do
it. Also gives you a leg up on variable word-length designs.
Didn't at least one of the more popular MPU designs employ a serial ALU?
TMS9900?
Serial ALU as a cost saver for low end makes sense in discrete transistor or
early SSI machines, like the PDP-8/L. It's hard to see how it would be useful
in MPUs, given that transistors are so much cheaper there.
It was the PDP-8/S (not 8/L) that had the serial ALU. The
8S was a discrete transistor machine, the 8/L used
integrated circuits. I think the core on the 8/S was also
really slow, like 6-8 us cycle time, so having the CPU take
its time made little difference.
Jon
