2 Oct
2020
2 Oct
'20
6:25 a.m.
On 2/10/20 10:20 am, Brent Hilpert via cctech wrote:
I'm not sure how unique this is to Zuse however.
The raw design presented in the Radio-Electronics/Edmund Berkeley Simon articles of
1949/50 presents this scheme,
although more complex (unoptimised) in the contact logic.
This is post-Zuse of course, but it's a question and investigation as to how the
design may have gotten from Zuse to the US/Berkeley in those years.
That is, I wonder if it's a design that was arrived at independently in multiple
places, or did it all derive from Zuse.
Charles Babbage designed a carry generate/propagate mechanism
("anticipating carriage") for the Analytical Engine which works in much
the same manner, though of course mechanically and in Base 10.
If the wheel rotated past 9 it set a lever which (later) triggered carry
on the next higher wheel. If the wheel was sitting at 9, an interposer
meant that any carry in would be transferred to the next higher wheel
(as well as rotating the wheel to 0.)
This is in contrast to the ripple carry mechanism on the Difference
Engine, which he knew restricted the speed.
I don't know when his designs were publicised but I doubt they had any
influence on Zuse and others of that era.
When I was figuring-out/recreating the design of
'Simon' some years ago, I optimised the RE/Simon adder design down considerably.
That's written up here, in the ALU/adder section:
http://madrona.ca/e/simon/imp.html
The schematic there presents the idea.
Some years later I ran across the Zuse design and found I was one optimisation short of
Zuse
(IIRC, one more contact could be optimised out and it would match the Zuse design).
I've been long meaning to add the Zuse circuit into that page to present the further
optimisation.
Please do! Perhaps you could phrase a description in terms of
generate
(A.B) and propagate (A+B)
--
Lawrence Wilkinson lawrence at ljw.me.uk
The IBM 360/30 page http://www.ljw.me.uk/ibm360