difference between CPU and DSP

The features of DSP:
   Harvard architecture
   hardware multiplier
   SIMD instruction
   special addressing mode(I haven't used it,but the documents say it
is used for DCT or FFT)
   DAG unit
   barrel shifter  (not sure)
   zero-overhead loop(ADI blckfin561 has this features, I don't know
the DSPs of other companies)
   large stage pipeline

ARM is a CPU, but after reading the documents, I find that ARM almost
has all above features,
I am told that CPU is for control applications, and DSP is for
computation-intensive applications
what architectural features make CPU suitable for control? branch
prediction? interrupt response?
MMU?(now DSPs also have MMUs)

Can anyone give me some information or internet links? thanks

Hello--

> Re: difference between CPU and DSP

Did you mean MPU (or MCU) and DSP?

>The features of DSP:
>   Harvard architecture
>   hardware multiplier
>   SIMD instruction
>   special addressing mode(I haven't used it,but the documents say it
>is used for DCT or FFT)
>   DAG unit
>   barrel shifter  (not sure)
>   zero-overhead loop(ADI blckfin561 has this features, I don't know
>the DSPs of other companies)
>   large stage pipeline


OK.

>ARM is a CPU,

ARM has a CPU. Do does DSP. So do all other microprocessors.

> but after reading the documents, I find that ARM almost
>has all above features,

ARM can do some DSP, so can some of the PC class pentium chips. But that
doesnt make it a Digital Signal Processor. Power management, clock rate,
MIPS,MMACS, on chip memory, specialized instruction sets etc. are matters
of degree and preciselt that which differentiates a specialized
accelerator(DSP) from a general purpose controller(ARM).

>I am told that CPU is for control applications, and DSP is for
>computation-intensive applications
>what architectural features make CPU suitable for control? branch
>prediction? interrupt response?
>MMU?(now DSPs also have MMUs)
>
>Can anyone give me some information or internet links? thanks

1] Try vliw.org and the associated book by Joseph Fisher.Its very good.

2] Try www.bdti.com for independent comparisons and benchmarking of latest
chips(DSP,MCU,MPU,RISC etc...) They have published a book called DSP
processor fundamentals, which is a very simple and useful introduction to
DSP architectures.

3] Try www.jimturley.com for an alternate view at things.

4] Try googling for "top 10 myths about Microprocessors."

--Bhooshan

hi,
       I WANT TO JOIN THIS GROUP
bhooshaniyer wrote:
> Hello--
>
> > Re: difference between CPU and DSP
>
> Did you mean MPU (or MCU) and DSP?
>
> >The features of DSP:
> >   Harvard architecture
> >   hardware multiplier
> >   SIMD instruction
> >   special addressing mode(I haven't used it,but the documents say it
> >is used for DCT or FFT)
> >   DAG unit
> >   barrel shifter  (not sure)
> >   zero-overhead loop(ADI blckfin561 has this features, I don't know
> >the DSPs of other companies)
> >   large stage pipeline
>
>
> OK.
>
> >ARM is a CPU,
>
> ARM has a CPU. Do does DSP. So do all other microprocessors.
>
> > but after reading the documents, I find that ARM almost
> >has all above features,
>
> ARM can do some DSP, so can some of the PC class pentium chips. But that
> doesnt make it a Digital Signal Processor. Power management, clock rate,
> MIPS,MMACS, on chip memory, specialized instruction sets etc. are matters
> of degree and preciselt that which differentiates a specialized
> accelerator(DSP) from a general purpose controller(ARM).
>
> >I am told that CPU is for control applications, and DSP is for
> >computation-intensive applications
> >what architectural features make CPU suitable for control? branch
> >prediction? interrupt response?
> >MMU?(now DSPs also have MMUs)
> >
> >Can anyone give me some information or internet links? thanks
>
> 1] Try vliw.org and the associated book by Joseph Fisher.Its very good.
>
> 2] Try www.bdti.com for independent comparisons and benchmarking of latest
> chips(DSP,MCU,MPU,RISC etc...) They have published a book called DSP
> processor fundamentals, which is a very simple and useful introduction to
> DSP architectures.
>
> 3] Try www.jimturley.com for an alternate view at things.
>
> 4] Try googling for "top 10 myths about Microprocessors."
> 
> --Bhooshan

bhooshaniyer wrote:
> Hello--
>
> > Re: difference between CPU and DSP
>
> Did you mean MPU (or MCU) and DSP?
>
> >The features of DSP:
> >   Harvard architecture
> >   hardware multiplier
> >   SIMD instruction
> >   special addressing mode(I haven't used it,but the documents say it
> >is used for DCT or FFT)
> >   DAG unit
> >   barrel shifter  (not sure)
> >   zero-overhead loop(ADI blckfin561 has this features, I don't know
> >the DSPs of other companies)
> >   large stage pipeline
>
>
> OK.
>
> >ARM is a CPU,
>
> ARM has a CPU. Do does DSP. So do all other microprocessors.
>
> > but after reading the documents, I find that ARM almost
> >has all above features,
>
> ARM can do some DSP, so can some of the PC class pentium chips. But that
> doesnt make it a Digital Signal Processor. Power management, clock rate,
> MIPS,MMACS, on chip memory, specialized instruction sets etc. are matters
> of degree and preciselt that which differentiates a specialized
> accelerator(DSP) from a general purpose controller(ARM).
>
> >I am told that CPU is for control applications, and DSP is for
> >computation-intensive applications
> >what architectural features make CPU suitable for control? branch
> >prediction? interrupt response?
> >MMU?(now DSPs also have MMUs)
> >
> >Can anyone give me some information or internet links? thanks
>
> 1] Try vliw.org and the associated book by Joseph Fisher.Its very good.
>
> 2] Try www.bdti.com for independent comparisons and benchmarking of latest
> chips(DSP,MCU,MPU,RISC etc...) They have published a book called DSP
> processor fundamentals, which is a very simple and useful introduction to
> DSP architectures.
>
> 3] Try www.jimturley.com for an alternate view at things.
>
> 4] Try googling for "top 10 myths about Microprocessors."
>
> --Bhooshan


The distinction between DSPs and generic MCUs (generic
microcontrollers) is rapidly diminishing.  I believe the distinction is
that MCUs generally tend to have more of a focus of peripheral support
providing different serial communications methods, more IO ports, PWM
and Input capture support, etc.  These features may or may not have
been available in any particular DSP.  DSPs on the other hand tended to
focus more on the math engines, and as you indicated hardware support
for looping, bus architectures that allow grabbing data from program
and data memory simultaneously (as would be used in multiplying ADC
data by a constant co-efficient) and hardware multipliers that take
fewer instruction cycles.

jayaprakashcareer@gmail.com wrote:
> hi,
>        I WANT TO JOIN THIS GROUP

Sorry, you need to know the password and secret handshake first.

bhooshaniyer wrote:

> Hello--
> 
> 
>>Re: difference between CPU and DSP
> 
> 
> Did you mean MPU (or MCU) and DSP?
> 
> 
>>The features of DSP:
>>  Harvard architecture
>>  hardware multiplier
>>  SIMD instruction
>>  special addressing mode(I haven't used it,but the documents say it
>>is used for DCT or FFT)
>>  DAG unit
>>  barrel shifter  (not sure)
>>  zero-overhead loop(ADI blckfin561 has this features, I don't know
>>the DSPs of other companies)
>>  large stage pipeline
> 
> 
> 
> OK.
> 
> 
>>ARM is a CPU,
> 
> 
> ARM has a CPU. Do does DSP. So do all other microprocessors.
> 
> 
>>but after reading the documents, I find that ARM almost
>>has all above features,
> 
> 
> ARM can do some DSP, so can some of the PC class pentium chips. But that
> doesnt make it a Digital Signal Processor. Power management, clock rate,
> MIPS,MMACS, on chip memory, specialized instruction sets etc. are matters
> of degree and preciselt that which differentiates a specialized
> accelerator(DSP) from a general purpose controller(ARM).
> 
Don't forget the 8051, as long as the signal is slow enough.  I've done 
real-time signal processing (for closed-loop control) with a 68HC11 
running a mighty 500 KIPS (kilo instructions per second).
> 
>>I am told that CPU is for control applications, and DSP is for
>>computation-intensive applications
>>what architectural features make CPU suitable for control? branch
>>prediction? interrupt response?
>>MMU?(now DSPs also have MMUs)
>>
>>Can anyone give me some information or internet links? thanks
> 
> 
> 1] Try vliw.org and the associated book by Joseph Fisher.Its very good.
> 
> 2] Try www.bdti.com for independent comparisons and benchmarking of latest
> chips(DSP,MCU,MPU,RISC etc...) They have published a book called DSP
> processor fundamentals, which is a very simple and useful introduction to
> DSP architectures.
> 
> 3] Try www.jimturley.com for an alternate view at things.
> 
> 4] Try googling for "top 10 myths about Microprocessors."
> 
> --Bhooshan
> 
> 


-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Posting from Google?  See http://cfaj.freeshell.org/google/

"Applied Control Theory for Embedded Systems" came out in April.
See details at http://www.wescottdesign.com/actfes/actfes.html

The difference between a CPU and a DSP is mostly in the
markets for which their design is optimized.  Often the market
needs intersect or overlap, thus so do the product families.

Some CPU architectures seem to have started catching
up with DSP's in the MACs and FFTs per system-cost and
mW power metrics.  One area where they still seem to differ
is in the area of bounded latency, which is often made
worse by the caches, TLBs, large pipelines and register
files which some CPU's use to run big applications faster.
However, low-cost low-power bounded latency is an absolute
requirement for many embedded real-time and streaming
data applications, more so than peak performance.


IMHO. YMMV.
-- 
rhn A.T nicholson d.0.t C-o-M

>The difference between a CPU and a DSP is mostly in the
>markets for which their design is optimized. 

Why do you keep saying CPU and DSPs? CPU stands for central processing
unit, which all microprocessors,including DSPs, have?

Iam wondering if you are touting some new abbreviation for CPU now.
--Bhooshan

bhooshaniyer wrote:
> >The difference between a CPU and a DSP is mostly in the
> >markets for which their design is optimized.
>
> Why do you keep saying CPU and DSPs?

Because they are marketed differently (even if you think
the technical meanings of the terms are identical or proper
subsets).  Sort of like the difference between marketing
bottled water versus Coke.

joggingsong@gmail.com wrote:
> The features of DSP:
>    Harvard architecture
>    hardware multiplier
>    SIMD instruction
>    special addressing mode(I haven't used it,but the documents say it
> is used for DCT or FFT)
>    DAG unit
>    barrel shifter  (not sure)
>    zero-overhead loop(ADI blckfin561 has this features, I don't know
> the DSPs of other companies)
>    large stage pipeline
>
> ARM is a CPU, but after reading the documents, I find that ARM almost
> has all above features,
> I am told that CPU is for control applications, and DSP is for
> computation-intensive applications
> what architectural features make CPU suitable for control? branch
> prediction? interrupt response?
> MMU?(now DSPs also have MMUs)
>
> Can anyone give me some information or internet links? thanks

I consider anything that has a single cycle MAC (easy part) and the
necessary supporting infrastructure to keep it continuously fed and
emptied (the hard part) from SRAM a DSP.

There are many pretend DSP's with single cycle MAC's but it takes 10
cycles to load them up and another 10 to empty them into SRAM, your FFT
really takes a hit on those critters.