From: perterm <perterm_at_vce.de>
Date: Fri, 16 Apr 2004 12:52:54 +0200

> Von: [IDC]Dragon
>
> In general, the potential for power savings due to less CPU utilization is
> small.

...

> You save quite a bit by really shutting off the disk instead of sending it
> to sleep (only possible with the AA-cell Recorders). This does 20mA for my
> disk, iirc. But the spinup is slower.

The cpu load and the disk-on-time can be related. Imagine the cpu is very
busy with scrolling, bitswapping and meter peeking while it also must fill
the mp3 buffer from disk. Then the time it takes to fill the mp3 buffer is
longer than it would be when the cpu didn't have to do anything else. Thus a
busy cpu can mean that the disk stays turned on for a longer period. That
may be a more significant power drain than the power the cpu itself
consumes.

It might be more efficiant to disable the peak meter and scrolling (which is
much more expensive than the peak meter) while the buffer is being filled.
Maybe it would be useful to program a little test that simply measures the
disk-on-time. Then we could measure the effect a busy lcd has on the
disk-on-time and estimate the benefits of keeping lcd traffic low while
filling the buffer.
Still I don't expect much of it because it's the spinup that is the worst
power eater.

Phil

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Received on 2004-04-16