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

Michael 'Mickey' Lauer <[email protected]>
Newsgroups gmane.comp.handhelds.openzaurus.devel
Organization Institute of Computer Science, University of Frankfurt
Message-ID <[email protected]>
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.

Hope that helps.
-- 
Regards,

Mickey.
------------------------------------------------------------------
Dipl.-Inf. Michael 'Mickey' Lauer <[email protected]>
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