[RC5] Re: A whole bunch of things

Kevin van Haaren KvanHaaren at HNTB.com
Fri Nov 21 15:14:30 EST 1997


there is no advantage on a PPC's to work in float.  Alpha's might get an
advantage since they're optimized for float.

Kevin

> -----Original Message-----
> From:	Jared McIntyre [SMTP:jmcintyre at DEPAUW.EDU]
> Sent:	Friday, November 21, 1997 2:25 PM
> To:	rc5-digest at llamas.net
> Subject:	[RC5] Re: A whole bunch of things
> 
> So what chips would be legit to try this on (especially the ones we
> could
> parrallel process with). And what is the chance that we could get
> someone
> to implement this. We could really do a lot more keys by crunching
> both
> ways.  My PPC is itching to do some floating point work.
> 
> jared
> 
> >     I posted a method for doing the all important rotates in FP.
> The
> >     modulo additions are trivial.  The only real trouble you'd have
> is on
> >     architectures with only one "full size" FP register or some
> (popular)
> >     idiotic architecture that uses a FPU *stack*.  Then you'd have
> to
> >     continually be loading and reloading "A" and "B" into the FPU
> >     register.
> >
> >     On (popular) idiotic hardware, I'd expect this to be no better
> than
> >     the rotateless clients.  However, this has the advantage of
> being
> >     parallelizable with the normal client on the same hardware.
> Some
> >     other platforms also allow parallelized FP execution.
> >            -- Eric Gindrup ! gindrup at Okway.okstate.edu
> ----------------------------------------------------------------------
> -------
> >     Nope.  Get an IEEE doubbe (80 bit mantissa).  Put two adjacent
> copies
> >     of the argument in the most significant bytes (setting the other
> two
> >     bytes to 0).  Call the byte position collections occupied by the
> two
> >     copies "high-order" and "low-order" indicating the relative
> >     significance of their bits.  Set the exponent to represent
> 2^-(32-k).
> >     Add 1.  This slides the bits we originally inserted by 32-k bits
> to
> >     the right.  The bits in the position called "low-order" are now
> the
> >     original argument shifted k bits to the left.
> >     If you want right shift, set the exponent to represent 2^-k
> instead.
> >            -- Eric Gindrup ! gindrup at okway.okstate.edu
> >
> 
> 
> 
> ___________________Schwartz____________jmcintyre at depauw.edu___
> 
> """"""
> O    O    from Allen Ginsberg's - Refrain
>   \/
>  ....     -   nobody cares when a man goes mad
>   ..          he is sorry, God is glad
>               shadow changes into bone
>               shadow changes into bone
> 
> 
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