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Re: MISC-d Digest V99 #87


Jeff Fox writes:

 > Interesting.  But who said that dsp-clusters are off topic.  I know

Thanks.

 > that DSP have large die and such but I don't see why a MISC cannot
 > be a DSP variant or that a DSP chip has to have more than a minimal
 > instruction set.  
 
The problem is that this is not about hardware design: there are
pretty useful *affordable* chips out there. Furthermore, while I
intend to go the Forth way, I don't want to keep the C people out. The 
more people participate, the better.

 > I can grasp the concept of an OpenSource paradigm.  A lot of Forth
 > projects have been of that nature.  Beowulf paradigm I don't quite
 > get.  Maybe I am missing something.  I think of Beowulf as just a
 > networked PC with software layers for multiprocesing on that platform.
 
Admittedly, it's no big deal, but the name "Beowulf" has become a
trademark/meme cluster. Whenever you say "I'd like to bring the
Beowulf to DSPs" more people will grok it.
 
 > If some DSP has networking hardware one could implement the software
 > layers that are used in Beowulf on the existing hardware there.  I
 > would expect it to reduce system performance by an order of
 > magnitude rather than boost it.  I just imagine that the layers

Sure, but IP stacks can be ridiculously compact (half a kiloword of
assembly), and there are tons of PVM/MPI software out there.

 > in Beowolf are typcial of the environment and might not be required
 > on the DSP.  
 
Of course not, but one needs an application base first.

 > If you have something that has functions of distributed shared memory
 > in hardware I would think you would want to try to remove extra software
 > layers to boost performance.  If you model the software after stuff

Definitely. This is one of SHARC nicer features: sending messages by
executing a machine instruction vs. kernel traps and NIC register banging.

 > that evolved getting network hardware designed to compete with hard
 > disks to act like a multprocessor bus the software might have layers
 > of complexity that you don't need if the DSPs were designed to be
 > clustered in the first place.
 
True, but one needs to get started somewhere. It makes definite sense
to initially let a (small) Beowulf to get the hosting: as a number of
multi-DSP cards in PCI slots. If it catches on one can think about
interfacing video and EIDE devices and whatnot to the DSP.

 > I must be missing something.  Maybe I am just thinking of the details
 > of the Beowulf implementation that are system specific too much instead
 > of just the idea of a standard way using clusters.
 > 
 > If you are talking about the multiprocessing software being Forth
 > or looking like a MISC variant to a user why would that be off
 > topic in the MISC mail list?  

We can definitely crosspost relevant materials both here and there. 

 > >Discussion topics include both hardware and software issues.
 > >
 > >Regards,
 > >
 > >Eugene Leitl
 >