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[f-cpu] Re: Floating-Point?



hi !

Juergen Goeritz wrote:
> On Mon, 13 Aug 2001, Yann Guidon wrote:
> > > do you have a link to basic floating point implementations
> > > that can be used to begin with a pipeline fpu unit?
> >
> > There are some docs floating around on Internet but nothing
> > that could do the trick for the FC0 (due to its specific structure).
> > superpipeline + SIMD is not easy to do.
> > In fact i had seen nothing reallyinteresting or coherent concerning
> > FP execution units. At one point i intended to use a logarithmic
> > addition unit developped at the Cambridge University, so we could
> > do a simili-FP with only a few added units. The route is prepared
> > but i don't know if we'll go that far.
> 
> Hi Yann,
> 
> just thinking about a vector floating point unit with
> superpipelined operation for fast tensor computation.
> I don't want to use the Meiko FPU from the microSparc
> architecture because it's not a really open hardware.
> So far I did only find some verilog implementations
> and some 24bit stuff.

shit, it looks like we'll have to reinvent the wheel.

there are a lot of data scattered on the Net and we'll have to play
the puzzle game once again :-/

However, i KNOW that there is a 32-bit LNS adder thats works.
it is not GPL unfortunately but i had spoken to the professor
who led the work at Cambridge (UK). we have not found an agreement yet
but provided this unit is available, it computes logarithmic base
addition of 32-bit numbers that are of equivalent acuracy as a 32 bit
IEEE FP number. The rest (div, mult, sqrt etc.) is done by the integer
units. i had links about this a few months ago, and even downloaded
the website with useful indications about the method : two parallel lookup
tables : one is the approximation and one is the correction, they are
combined by a few add and a half mutliply.


In fact, FP or LNS numbers are not yet worrysome. When the integer
execution core will be ready, a few modifications are enough to add
another unit.


> Greetings
> JG
WHYGEE
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