"glen herrmannsfeldt" <gah@[EMAIL PROTECTED]
> wrote in message
news:CZSdnfkDXvuBFyTeRVn-tg@[EMAIL PROTECTED]
> robin wrote:
>
> (snip regarding HER, HDR, and the lack of normalization in the early
> versions of S/360.)
>
> > Except, of course, initially for HER and HDR. The 1964 Principles of
Operation
> > makes this clear.
> > Indeed, the RCA Spectra (and the EE System 4 which was a licenced
copy)
> > did not normalize in the case of HER and HDR. That never changed for
the
> > EE Systrem 4 (I don't know what RCA subsequently did for the Spectra.)
> > Nor did the System 4 retrofit a guard digit on d.p.
>
> Well, one could always add zero, still probably faster than divide,
Definitely faster than divide, but that took an extra instruction (4
bytes)
and possibly an extra constant (4 or 8 bytes) when there was precious
little store to hold the extras.
The real problem with HER and HDR, however, with the unnormalized
version was the loss of precision if the most-significant nibble ws 1.
> but if you always need to do that it makes (made) more sense to fix it.
>
> It might be that there would be use for HU and HW, the obvious
> mnemonics for unnormalized versions, but I can't think of them right
now.
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