[geeks] examples of vector processors (vs scalar

[Dave McGuire]

On August 5, dave at cca.org wrote:
> If the data is laid out properly in memory, can you keep the
> vector units working continuously, while streaming all the
> data in and out to memory?

  Generally yes, but I don't know offhand how many memory paths each
processor type has.  I will see if I have that info anywhere.

  One of the big deals behind Cray machines is memory performance...Lots
of systems don't have enough memory bandwidth to keep their processors
fed.  Such isn't the case with Crays.

> Also - did some of the Crays have multiple FP units, so
> they could actually run some of the vector elements in
> parellel?

  Yup.  Take, for example, the smallest, slowest, cheapest Cray
supercomputer, the YMP-EL, circa 1991 or so.  Each of its processors
(there can be up to eight) has four functional units, each of which
can perform one FP add or one FP multiply per clock cycle.

> Is that what the SV1's CPU configuration thing
> is all about?

  I don't know much about the SV1's internals, sorry...never had a
chance to futz with one.

      -Dave

-- 
Dave McGuire                     "I haven't worn pants in 14 months!"
St. Petersburg, FL                                   -Pete Wargo