Re: CRAY

"Dick Hendrickson" <dick.hendrickson@[EMAIL PROTECTED]
> wrote in message
news:dvxbk.186679$SV4.107189@[EMAIL PROTECTED]
> robin wrote:

> > If the upper n bits of product were incorrect, you'd have to say that
the
> > multiplier was broken.
>
> When you multiply two 48 bit values (the Cray
> mantissa) you potentially get a 96 bit product.  The
> Cray hardware only computed about 60 bits in the product
> and added in a couple of "statistical" round to make up
> for the missing 30 or so bits.  This was then trimmed down
> to 48 bits.  It was accurate to 48 bits in the majority
> of cases.  I think it was always accurate to 46 or so
> bits.  Whether that is foolish or broken is a judgment
> call.

I'd call it broken.
Makes it difficult to get integer results.
Makes it difficult to get a double precision product.