[sdiy] dsPIC33 question..

[karl dalen]

Well, you are most likely right but it depends what we
meant by high performance DSP work? At Texas C6xxx performance?

As you said a Cortex or ARM7 run at 72Mhz cant execute from
flash at full speed but neither could a dsPIC at this speed,
nor could any other as im aware of do no matter kind of DSP,
restriction lies at Flash technology!?

However if the Cortex/ARM7 was to reduce its speed one can
indeed execute from Flash at same or slightely faster then a
30Mhz dsPIC. But this is a bit on wandering among the details.
LPC has adiffrent sceme in terms of executing from Flash.

Cortex is a bit faster then ARM7 its also easyier to program.
If one wants fast short DSP routines one can place then in RAM
and execute from there but yeat again as you say there are 
limitations, ther are many issues, but as Anti H once mentioned
there are pleny of power in a ARM7 etc to do a complete
4 OSC + filter wavetable synth, so it all depends on what
we meant by high DSP performance.! 

>When it comes to DSP however they're seriously lacking in areas
>where the dsPIC has better resources.

Please, im interessted to hear your finds?

> dsPIC has a true MAC with complex addressing modes
And Cortex has MAC for 64 bit operations. And on and on! :-)

dsPIC is more efficent then ARM7, Eric is right in that but
again it all comes down what do we want to do with the MCUs?

I dont think speed is a problem anymore or whats on the die
its the tools that's a drag!

I think the 28 pin DIP dsPIC is a neat thing, btw!  

KD

--- Den tis 2008-12-02 skrev Eric Brombaugh <ebrombaugh1 at cox.net>:

> Från: Eric Brombaugh <ebrombaugh1 at cox.net>
> Ämne: Re: [sdiy] dsPIC33 question..
> Till: dalenkarl at yahoo.se
> Kopia: synth-diy at dropmix.xs4all.nl
> Datum: tisdag 2 december 2008 22.46
> karl dalen wrote:
> 
> > Btw a ARM7 has way more DSP power then an dsPIC.
> 
> I disagree.
> 
> First let me preface this - I've used both in pro
> applications (ie - I got paid to do the work) and I like
> both. I wouldn't try to use the ARM for high-performance
> DSP though, and I wouldn't use the dsPIC for complex
> low-power applications.
> 
> ARM7 is a great processor for large embedded projects. You
> can do a lot with them and they're very inexpensive. The
> architecture supports a lot of memory and typically they
> have very low power operating modes. 32-bit native data
> format is great for high resolution math operations. When it
> comes to DSP however they're seriously lacking in areas
> where the dsPIC has better resources.
> 
> dsPIC has a true MAC with complex addressing modes
> (dual-access data buses, prefetching, pointer updating, etc)
> which enable single-cycle operations on FIR and IIR filters.
> dsPIC can execute from flash at full speed - most ARM7s need
> complex caching and Thumb code to do this. ARM7 has fairly
> complex interrupt processing overhead while dsPIC has
> interrupt vectoring built in to the heart of its execution
> unit which enables very fast response.
> 
> Bottom line: each processor has its strengths. While you
> can do DSP on an ARM7, the dsPIC can do many (not all) kinds
> of DSP better than an ARM7.
> 
> If you need high-resolution, high-speed DSP for things like
> hi-fi audio, video or radio applications, you probably
> shouldn't be considering either of these though.
> 
> Eric


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