28 Jun
2004
28 Jun
'04
3:14 p.m.
Then there are special cases: the Cray and Alpha
integer units, which
don't offer divide at all. Instead, you're supposed to multiply by
the reciprocal of the divisor. This works well, because you can
actually do that faster than the straightforward one bit at a time
division even if you have to calculate the reciprocal at runtime.
Do you know how this is done (at least the fancy ways of doing it)? I
assume there are shortcuts, as the Cray 1/x pipes were not hugely long
compared with the other pipes (there has to be some magic somewhere).
William Donzelli
aw288(a)osfn.org