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?
Right!
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.
Jon
