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Re: [Xylo-SDR] Firewire, DSP and FPGA on one module
Yes, Bob. It is too difficult to write assembly code which makes use
of all the eight functional units of the C6x architecture, though it
can be done and we do it many a times. But with proper pragmas, C code
can be written which are probably 10-20% close in cycles to hand
optimized assembler code.
I understand that afew students at a German University is doing a gcc
port. With the new tree-ssa optimizations available in the gcc, it
could probably be possible to use the software pipelining optimizer in
gcc. I do not fully understand how this works, but looks like people
have used this new feature in gcc to actually write optimizing
compilers for other VLIW architectures like the Itanium. Since I do
not run Windows at home (for the past eight years or so), I am waiting
for the day when free tools are available for DSPs. It's not that I am
going to modify the sources, but the fact that there is a community
behind it to fix the problems is a great thing, like the way
SDR1k/powerSDR project works.
On 12/19/05, Robert McGwier <email@example.com> wrote:
> The 67XX is the very first DSP chip where I believed it was actually
> necessary to use a development system rather than writing assembler.
> The very long instruction word, sometimes executing 16 instructions in
> parallel (!!!!!) makes it almost a requirement to use computer aided
> optimization tools to reorder instructions. It is understandable why
> these tools are not free. I also think that nearly four thousand
> dollars a seat is absolutely outrageous. Thank goodness I get an
> educational discount. I played these games by hand when I was
> programming the DSP56001 (which also had multiple functional units
> running in parallel) but it was manageable. The other thing I like
> about it is that it also does fixed point natively and it really
> blisters in those modes. For truly high speed operation, it is critical
> to use optimized libraries for the "big things".
> Ramakrishnan Muthukrishnan wrote:
> >another big problem with using C-incapable DSP chips is the fact that
> >once these are obsolete, it needs to be ported to the new processor.
> >C67x is a nice part. I use C64x in my day job and have used all the
> >other 16-bit fixed point TI parts too (I work for TI). If there were
> >free tools, I would have definitely prefered to use a C67xx part for
> >PIC-A-STAR, which would have given me more MIPS to do more interesting
> >stuff and also write everything with C.
> Laziness is the number one inspiration for ingenuity. Guilty as charged!
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73, Ramakrishnan - VU3RDD