Don't have any firm answers, but a few observations:
1. Running code from RAM may not be the same as running code from ROM. As
an experiment, try using one of the programs out there to load your code
into flash. Then, see if that affects your power estimates. That would be
an interesting result.
2. Last I knew, POSE did some tricky for certain OS functions (like
trapping them, and then running native code instead of the OS code). It
doesn't do this too much, but I thought I remember hearing about this.
Maybe it's just pen events...hmmmmm
Good luck!
---
--On Thursday, June 22, 2000 12:01 PM -0700 Laurent Lazard
<[EMAIL PROTECTED]> wrote:
> We are currently working on a tool to help developers evaluate the power
> consumption of their program.
>
> The principle is simple: when the program is executed on the POSE
> emulator, we stored the different opcodes executed and then associate
> each of these opcodes with an energy. At the end we just add to get the
> results.
>
> To do this, the energy was previously calculated by executing each
> instruction in an infinite loop, measure the current drawn and then
> multiply by the voltage (constant = 3V), and the time (number of cycles /
> clock frequency).
>
> This work really well for pieces of C code: When we execute part of C
> codes and compare the actual current drawn to the estimated one, we get
> less than five percent difference.
>
> The problem comes when we put some OS calls in the code. The actual
> current measured is 30 to 40 % less then the predicted one. This is wierd
> because we are still dumping the opcodes executed during a call of the OS
> correctly so we should get good results.
>
> My questions are the following:
> - is there any mechanism that is not implemented in the pose
> emulator ?
> - is there a doze mode where the processor put in a low power
> consumption state that would be used when an API is called ?
> - Where else could this difference come from ?
>
> We are also looking for two things:
>
> - benchmarks to evaluate the accuracy of our simulator (we
> will
> compare the expected current to the real measured one).
> - applications such as file compression, file
> encryption/decryption, FFT computation (we'll try to optimize their energy
> consumption).
>
> Is there any place I could find some of these ?
>
>
>
> Thank you in advance for your help. If we judge this program accurate
> enough we'll certainly make its source public...
>
>
> laurent lazard
> master student at Oregon State University, ECE department
>
>
>
>
>
> --
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