robin wrote:
> "John W. Kennedy" <jwkenne@[EMAIL PROTECTED]
> wrote in message
> news:vYypf.39224$L7.37622@[EMAIL PROTECTED]
>
>> The guard digit was added to double precision, postnormalization was
>> added to the HER and HDR instructions, and the behavior of overflow and
>> underflow was altered.
>
> The HE, HER, HD, HDR set was a glaring design error - a faux pas.
> That it failed to post-normalise meant that it couldn't be used
> in a loop to divide by, say, 32.
There never was an HE or HD instruction.
The main intention of the HER and HDR instructions was to accelerate
taking square roots.
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.
Some of the mistakes were corrected in the 1967 re-engineering, but
others (most grossly, the hexadecimal orientation) had to wait for
IEEE-754.
--
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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