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Re: [f-cpu] the wrong way (or not?) concerning FP



On Tue, 28 Aug 2001, Yann Guidon wrote:

> i would preferably go for the last solution, unless someone
> (a big genius) creates a very very good FP unit that performs
> complex operations in a non blocking way. THAT is a challenge
> (and a very interesting one).

What do you mean by complex operations?
sqrt(), log(), cos(), sin(), ...?

I think a floating unit will be fine with add, sub, mul, div
and maybe muladd. And I expect that it could be designed in
pipelined operation to give single cycle average execution
time. A 64 bit floating number unit would be just enough for
a start because you can convert any AD sampled 32bit integer
value into this format... Who needs more accuracy?

So why divide into integer and floating unit? Add those
basic floating functionality to *the* f-cpu unit.

If you want to add the complex function stuff like sin()
it gets more complicated and you get rid of pipelining the
instructions due to longer delays for the results and reuse
of the units. It will be more of a microcode thing then or
better say it this way, you end up with ordinary FPU design.

But actually most brute force problems I know don't have a
need for the complex functions but for a high performance
in basic arithmetics. Complex functions could be emulated
by software anyway. Am I right? 

Are there any intelligent algorithms for fast emulation of
the complex functions? This exceeds my experience (logic,
network and software design on all layers) but I would
volunteer on this part ;-)

JG

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