🚀 go-pugleaf

In article <1991May13.211555.28824@rice.edu>, preston@ariel.rice.edu (Preston Briggs) writes:
> hrubin@pop.stat.purdue.edu (Herman Rubin) writes:

			.....................

> If you want to take advantage of new architectures and implementations,
> your probably going to have to rethink some of your old assumptions.
> For example, in the old days, FP was much more expensive than integer
> arithmetic.  Now they are about the same.  In the old days, FP was
> more expensive than memory accesses.  Now FP is generally cheaper.

For the earliest machines with FP hardware, FP multiplication/division
was usually slightly faster than integer, because of the reduced 
accuracy, and addition/subtraction slower, because of the need for
shifts and normalizations.  Any FP unit is essentially an integer
unit with a few additional features needed to handle the exponent.

The only reason that integer arithmetic, especially multiplication
and division, are so expensive, is that they are done in separate
units, and these units are not designed with the concerns going into
the FP units.  Now division is, admittedly, a major headache, but is
there any good reason not to use essentially the same hardware for
integer and floating multiplication?  Some machines do not even have
separate integer arithmetic, but this can only be done if normalization
is not forced.  Is the one bit gained by forcing normalization worth
the problems caused?

I see no prospects whatever for speeding up memory accesses, except 
what can be gained by pipelining, multiple accesses, and burst mode.
-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (Internet, bitnet)   {purdue,pur-ee}!l.cc!hrubin(UUCP)