RE: [fpu] FPU operations

["Rudolf Usselmann" <russelmann@hotmail.com>]

>From: owner-fpu@opencores.org [mailto:owner-fpu@opencores.org]On Behalf
>Of Damjan Lampret
>
....
>
> > 6. I think we should provide SNAN when NAN is one of
> > the comparison operands but also we should produce
> > false for this kind of operation. This is even if the
> > standard does not requier it but it will give the
> > software more control.
> > I don't know. Instead I have a question. Who decides what kind of NAN
>is produced - QNAN or SNAN. Is this set in FP control register or is
>there some kind of protocol in stanard for this? Maybe different FP
>insns?

The standard only specifies that there should be definite values for
both Q and S NAN. But it does not specify exactly how to distinguish.
A semi-standard has evolved (based on Intel implementations):
SNAN has highest bit (bit 22) in the fraction (mantissa) section set,
and QNAN has it cleared.

....
>
>BTW since Rudi is working on its own and Jamil on its own FPU. How
>about more closer development where both FPU would be basically the
>same except of the HDL used. This way there would be one document, one
>'C' (or Java) test vector generator, easier to fix bugs etc. And more
>team spirit !

That doesn't make any sense. There should be one implementation only, you
can do easy (perhaps soon automatic) translations between languages.

Since Jamil is always doing his own thing, and was on the project before
me, I'll stop working on my cores, and let Jamil build them. I have some
other ideas I'd like to follow anyway and I didn't fit in to this specific
working environment anyway. Watch the main mailing list for some cool things
to come !!!!  Just make sure the OR1K will be build, I'll need it in my
next project !!!!

>--damjan

I'll stay in the list for another week or two, in case I can help with any
questions. But will definitely sign off after that

Cheers,
rudi

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