hardware multiply/divide functionality in CPUs

Jules Richardson jules.richardson99 at gmail.com
Mon Mar 7 18:08:47 CST 2011


Richard wrote:
> In article <4D756F00.6000706 at gmail.com>,
>     Jules Richardson <jules.richardson99 at gmail.com> writes:
> 
>> Yes, anything that includes a dedicated multiply or divide instruction as
>> part of the instruction set; I suspect a lot of the early implementations
>> fall into the "simple shift-add" that I mentioned due to the lack/cost of
>> silicon.
> 
> (BTW, line lengths of about 75 or so characters are *much* more
> friendly to quoting than line lenghts of *exactly* 80 characters.)

Hmm, good point. I had it set to 78 (TB's default), now changed to 75 though :)

> 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...

cheers

Jules






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