70's computers

[Jon Elson]

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 at 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