Re: [f-cpu] Re: Floating-Point

[Glenn Alexander <jxmlisa@online.ln.cn>]

> On Tue, Aug 21, 2001 at 12:09:37AM -0400, nicO wrote:
> The manual says:
> 
>         00      32-bit
>         01      64-bit
>         1x      unassigned

Shouldn't we have SRs (yeah I know) to define the sizes the same as for the 
int unit? Then the software can choose the FP widths that it wants. Default 
might be:

00	32bit
01	64 bit
10	80 bit (optional and I don't like binary numbers that have more than one 1 
in them and if the registers are 128 bit anyway, why not just bump up the 
resolution?)
11	128 bit (optional, but better than 80bit ;-)

That's four more SRs, but they would only have to be state-saved if they were 
being used.

Alternatively, just use the Int SRs for the float width.
(we waste the 8 value - assuming we are using the defaults abd assuming 
no-one wants 8-bit floats (well someone might!) - and 16 bit floats are of 
dubious value at best, we would also have to re-define int types away if we 
wanted >64 bit floats and 80bit floats would be out (but I don't mind that - 
not if 128bit is avaliable) ) It depends on how many int-widths are likely to 
be used by the a program segment using floats, I guess.  Is a mix adding up 
to four enough?


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Glenn Alexander - The man with no surname and a silly hat.
(B.Teach, B.Ed Major IT Education, University of Wollongong Australia)
(Now avaliable in China!)

http://members.ozemail.com.au/~glenalec (last update: 2001.07.29)

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