On Wed, 27 Jan 2010, Javier S. Pedro wrote:
When I got my N900, one of the first things I noticed is that (as measured by
powertop) I could never get a 100% ratio at 600 Mhz, but more like 95%. I
quickly assumed this was the safeguard for the issue Igor Stoppa talked about
at the Maemo Summit.
However, I've noticed today (as suggested by a tmo post) that the above is not
caused by any special modification in the kernel, but rather because of the
CPU idling while waiting for the SGX / some other hw (so, testing methodology
failure on my part :) ).
Thus, given any task bounded by raw CPU throughput, the device will happily
clock itself at 600Mhz, even for hours. Doesn't that contradict what Igor said
at the summit?
At least for 30 minutes, there appear to be no 'safeguards':
N900:~# date ; cat /sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state ; for
i in ` seq 1 1000` ; do bzip2 -c9 /lib/libc-2.5.so > /dev/null ; done ; cat
/sys/devices/system/cpu/cpu0/cpufreq/stats/time_in_state ; date
Wed Jan 27 15:35:32 IST 2010
600000 43683
550000 487
500000 17132
250000 1164197
600000 254442
550000 487
500000 17132
250000 1164200
Wed Jan 27 16:10:39 IST 2010
This represents more than 99.99% of 35 minutes at 600MHz.
Note that I ran this test with no SIM, screen off, not charging and wifi
connected, but with practically no traffic. The device got only slightly
warm, but it was hardly noticeable, so I guess that the power draw of
the CPU, even at 600MHz does not have a large effect the system.
BTW, is there a temperature sensor somewhere in the system like there is
in the N810?
--
Matan Ziv-Av. ma...@svgalib.org
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