hardware multiply/divide functionality in CPUs

Richard legalize at xmission.com
Mon Mar 7 18:08:54 CST 2011


In article <4D75738F.1000504 at gmail.com>,
    Jules Richardson <jules.richardson99 at gmail.com> writes:

> > I don't think the multiply implementation in the IBM 701 was shift/add
> > microcode variety.  That wouldn't have been very performant for its
> > intended purpose (scientific computing).
> 
> I'll have to have a look online and see if I can find any details. I see 
> that Booth's algorithm was 1951 - much earlier than I expected and a year 
> before the 701. I'm not sure when Wallace trees showed up...

There's quite a bit of documentation on the 7090 on bitsavers; not
sure about the earlier models, though.  For the 701 it could be that
shift/add was the best they had at the time.  By the time we hit the
7090 I suspect they were doing better things, but I'm by no means any
sort of expert on IBM stuff.  I only recently learned about the 7090.
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