Interested in UNIVAC 9000 Series (and IBM 360)

Jon Elson elson at
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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