Rockbox mail archive
Subject: Power off testing - current and spinup time
From: Nuutti Kotivuori (naked_at_iki.fi)
I did a few tests with the hard drive power-off toggle and this is what
I came up with. My hard drive is: FUJITSU MHN2200AT.
These tests were made with bad equipment under bad circumstances - I
can replicate the results easily, so they should have an internal
consistency, but do not expect them to correlate to anybody else's
test results :-) The unit is A, but it's not really relevant since the
meter shows something way different.
Playing, backlight off, HD off: 0.07
Playing, backlight on, HD off: 0.11
Playing, backlight off, HD sleep: 0.08
Playing, backlight on, HD sleep: 0.13
(all the rest are backlight off
Booting up : 0.46
HD spun up and reading :~0.50
Spinning up peak power : 0.64
HD just before shutting down : 0.21
So, there is a difference between HD sleep and HD off. And that was
basically what I wanted to know.
Then I made some timing tests between hard drive power-off and
sleep. Some of these are taken by hand, so they are not too reliable.
In sleep mode, when ever the unit needs to read more, the hard drive
led will light up, the drive will spin up, the led will flash a bit,
and then go dark and the drive spins down again.
Spin-up time given by firmware : constant 20ms
There's gotta be a bug of some sort there, I could never see anything
else in the timing by the firmware.
Total time taken by one buffer fill : 3.1 s
In power-off mode, the behaviour is a lot different. First the hard
drive led will light up, then the drive will spin up - but it will
take around 5 seconds for the drive to spin up. Then the led goes dark
again for about a second. And after that it lights up again for a
couple seconds or less.
Spin-up time given by firmware (1) : 5100 ms
Spin-up time given by firmware (2) : 1900 ms
The first spin up time will show in the space between when the led
goes dark - and the second time will show after the second read is
finished. Then on to manual timings.
Time taken by first spin-up : 5.3 s
Delay between spin-ups : 2.2 s
Time taken by second spin-up : 1.4 s
Total time taken by one buffer fill : 8.9 s
That last total time actually is taken from a separate timing, it just
happens to hit exactly the same values.
With the power-off enabled, all my 256-kbit MP3's were breaking
up. Sometimes it was just a pause in playing, sometimes the sound
stopped altogether and would not come back until after another
I had to increase the low-water mark considerably, to take into
account the long spin-up times. That made performance relatively good,
but there was one obvious difference. It might have been for the still
inadequate low-water mark, but whenever I moved around with my player,
the loading started to break up. When I was walking, I hardly ever
heard any sound even. So it could be that the power-off spin-up is
more easily disturbed by movement.
I'm not sure what to make of all this, results are weird. But atleast
right now, power-off is not for me. Because of the long spin-up time,
the low-water mark problems and the relatively small power savings -
it doesn't seem worth it.
Hopefully this helps some.
Page was last modified "Jan 10 2012" The Rockbox Crew