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

[Holger Schurig]

> 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.

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

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



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



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

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

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



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