Re: How to compare computing power of microcontrollers?

On 30 Aug 2005 09:01:28 -0700, the renowned "Eric"
<ericjohnholland@xxxxxxxxxxx> wrote:

>If you don't have hardware for both, I would write a piece of assembly
>code "on paper". This code should be represntative of a function that
>you will be doing for your application (ie. 16 bit multiplication and
>trig). And add up the number of clock cycles it would take each
>processor to run the same piece of code.
>
>This calculations assumes each processor has similar instructions and
>the compilers you use have a similar optimization routine.
>
>You know the # of clock cycles and the frequency, you can then evaluate
>which processor has a better performance for your application.
>
>It is time consuming, but without looking at the Datapath / Instruction
>cycles you can't evaluate the performance.
>
>Example: a processor may run at a faster clock frequency, but if the
>instructions you are using aren't pipelined well your just burning up
>power and not gaining performance.
>
>Multiplication tends to be one of the instructions that is poorly
>pipelined in smaller cpus. So the # of instructions that MULT takes
>might be a good enough benchmark for your application.
>
>Good Luck,
>Eric

IIRC, the AVR has an 8 x 8 multipler, wheras the ARM core has a wider
multiplier (32 x 8?) and microcode to do 32 x 32 multiplies. By the
time you assemble all the partial products with the AVR, the
difference in speed might be quite large for multiply.

Personally, I'd write a little chunk or two of code and simulate it.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@xxxxxxxxxxxx Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
.

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