Home > Archive > ASM370 > January 2006 > Re: S/360 HER, HDR
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Re: S/360 HER, HDR
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| "glen herrmannsfeldt" <gah@ugcs.caltech.edu> wrote in message
news:CZSdnfkDXvuBFyTeRVn-tg@comcast.com...
> robin wrote:
>
> (snip regarding HER, HDR, and the lack of normalization in the early
> versions of S/360.)
>
Operation[color=darkred]
>
> 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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