I suppose you could test each nybble for zero, then equate a 16-element LUT
on nybbles not zero?
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On Fri, Apr 5, 2019 at 11:59 AM Kyle Owen via cctalk <cctalk at classiccmp.org>
Just wondering if anyone has come up with a fast way
to count the number of
1s in a word on a PDP-8. The obvious way is looping 12 times, rotating the
word through the link or sign bit, incrementing a count based on the value
of the link or sign.
With a small lookup table, you can reduce the total number of loops by
counting multiple groups of bits at a time, but this of course comes with
the cost of using more memory. Any other suggestions?