Re: Sharp Zaurus sl-6000 & Tomcat 5.x

On 4/12/06, Michael 'Mickey' Lauer
<[email protected]> wrote:
> Am Mittwoch, den 12.04.2006, 18:10 -0400 schrieb Scott Bronson:
> > I assume it emulates an FPU in software.
>
> Right. Then again, that's what HardFloat does as well, since the arm4[5]
> lacks an FPU.
>
> >  Can anyone say why the SharpROMs don't need it
>
> It's not "don't need", it's "can't do it". SoftFloat is a recent joint
> achievement by the gcc and glibc teams - the ancient toolchains the
> Sharp guys use just can't do that.
>
> > and how it makes OZ faster?
>
> A slightly simplified picture:
>
> HardFloat: a floating point operation generates a trap instruction which
> the kernel intercepts and handles. This needs context switches and the
> FPU emulation in the kernel is old and slow.
>
> SoftFloat: gcc/glibc insert appropriate instructions which handle FPU
> operations "in-place", no trap instruction, no context switch, no kernel
> involved. This is 1000% faster.
>
> >  What are the benefits/drawbacks?
>
> Benefits: see above.
> Drawbacks: needs recompilation.
>

I definately saw a huge speed increase when OZ started to use SoftFloat.

--
Justin Patrin


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