"John W. Kennedy" <jwkenne@[EMAIL PROTECTED]
> wrote in message
news:s7Vpf.39983$L7.34049@[EMAIL PROTECTED]
> robin wrote:
>
> The main intention of the HER and HDR instructions was to accelerate
> taking square roots.
First time I have heard of that one.
Division by 2 was and still is a fairly common operation
(averaging, etc) and given that float division took
an extraordinarily long time, HER and HDR were
golden op****tunities to speed up algorithms, if only
compilers would use them.
> It is very well known that the entire 360 FP feature could have used
> some input from numerical analysts; it's shot full of design defects.
When the S/360 was designed (1964), hardware was expensive,
and a hexadecimal mantissa minimised the hardware and,
in particular, reduced ****fting time [for normalization] to
a minimum.
> Some of the mistakes were corrected in the 1967 re-engineering, but
> others (most grossly, the hexadecimal orientation) had to wait for
IEEE-754.
Like I said, hex mantissa was a design that maximised speed and
minimised cost. IMHO it was a reasonable compromise.
> --
> John W. Kennedy
> "But now is a new thing which is very old--
> that the rich make themselves richer and not poorer,
> which is the true Gospel, for the poor's sake."
> -- Charles Williams. "Judgement at Chelmsford"
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