[Asterisk-Dev] Asterisk Hardware Platform - Intel x86 versus Intel RISC Xscale (ARM)

[Miroslav Nachev]

   Hi,

   I think that there are no needs of FPU, because the faster way to
do speech codecs is using integrated DSP through Micro Signal
Architecture (MSA).
   For example G.729 can be done using FPU for 100 MIPS. The same can
be done using DSP for 12 - 20 MIPS.


   Best Regards,
   Miroslav Nachev

>> Does that include FP hardware?  I don't believe that any of the PDA
>> Xscales do, I assume that at least some codecs need FP for compression;
>> without floating point hardware, it's going to be really slow.

HS> The Intel PXA2xx chips doesn't have a FPU. I don't know about the network
HS> Xscale thingies, but AFAIK they have two network interfaces, more than
HS> one independend DMA data shouvlers, PCI bus interface. Usually you don't
HS> need a FPU there ...

HS> PXA27x has some SIMD features, something similar to the MMX extensions for
HS> x86 processors.



HS> Back to FPU. If there is no FPU, then you have two options on ARM:



HS> Let the compiler emit FPU instructions and let these instructions be
HS> catched via exceptions from the Linux-Kernel and emulated. There are two
HS> of those FPU emulators out, NWFPE and FastFPE. NWFPU comes directly with
HS> Linux 2.6, FastFPE is external.

HS> This is the mode a Sharp Zaurus works out-of-the-box.

HS> It's somewhat slow, because you always get exceptions ...



HS> Or create a new set of compilation environment, where the 
HS> arm-linux-gcc/glibc combinations doesn't generate the FPU opcodes, but
HS> where it calls directly fpu emulation code in the glibc. This is the mode
HS> of operation that most users of OpenEmbedded.org (e.g. OpenSimpad,
HS> OpenZaurus, OpenMNCI etc) are now using.

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