Interested in UNIVAC 9000 Series (and IBM 360)
elson at pico-systems.com
Fri Nov 18 21:59:33 CST 2016
On 11/18/2016 06:04 PM, Chuck Guzis wrote:
> On 11/18/2016 03:15 PM, Jon Elson wrote:
>> OH, yeah! Besides the limited instruction set, short registers only
>> half populated, etc., did you know that the 360/20 did not have an
>> adder? It could only increment/decrement. The data paths were only
>> 4 bits wide, so to add a 3 in register A to a 5 in register B, it
>> decremented A and incremented B until A went negative. It did this
>> for each nibble. I'm guessing a 16-bit add took over 100 us. I'd
>> ALMOST reject calling this a COMPUTER!
> So not even as smart as a 1620 CADET, which did arithmetic via TLU?
> I guess I could believe that for register arithmetic, but did it do the
> same for memory-to-memory packed decimal operations?
Yes, I think it had to, as it had no adder. Had to be
incomprehensibly slow. I guess it would load the memory to
an internal register a piece at a time.
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