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From: ahosyney on 3 Apr 2008 12:35
On Mar 26, 4:24 am, Philip Potter <p...(a)doc.ic.ac.uk> wrote:
> ahosyney wrote:
>
> [Powerestimationusing XPower and ModelSim]
>
> > To Clarify this I started with an array size of 10 integers, this
> > array requires 887 clock cycles to be sorted and the total estimated
> >powerconsumption was around 488.65 mW. When I increased the array
> > size to 20 integers (which requires 3069 clock cycles to be sorted)
> > the estimatedpowerconsumption was 492.28mW with increase of about
> > 3.5 mW. When I increased the number of integers to 40 (11298 clock
> > cycles are needed to sort that), thepowerconsumption just increased
> > by around 2mW to be 494.29mW. When I raised the number of integers to
> > be 80 (43280 clock cycles to be sorted), thepowerconsumption was
> > reduced to 493mW. So it seems that the activities stored in the VCD
> > file are not affecting thepowerestimationas I expected.
>
> Why would you expect thepowerto be higher? Remember thatpoweris
> energy-per-second. I would expect the 20 integer case to require much
> the samepoweras the 10 integer case, but because it takes 3069/887
> times longer, it would use 3069/887 times more energy. A MicroBlaze
> doesn't consume more energy per instruction or energy per second just
> because the overall problem size is bigger!
>
> Note that had you used a different solution than a MicroBlaze or
> PowerPC, for example a parallel solution with greater parallelism for
> larger problem size, then it is entirely possible that thepower
> consumption would increase for larger problem sizes, while the time to
> solve the problem remained constant.

Thank you for your reply. I understand what you say. I excpected the
power to vary with much more amount than just the 2 mW. I'm using the
same array in all the test, so the number of swaps required will vary
from test to the other (data has changed), which should result in some
change in the power required to access the memory. Actually after
installing ISE 10.1 I got a variation of about 20mW. It seems that
XPowr 9.2i has a problem loading VCD files.

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