On 1/27/21 8:02 AM, Len Ovens wrote:
On Wed, 27 Jan 2021, Michael Jarosch wrote:
As soon as frequency switching was introduced we LAU were told, not
to use it to save xruns. And as far as I can tell, the rule still
valid. Is there a chance in the future that we can stop thinking
about it, because it just won't matter? Are we forced blowing loads
of energy or do we spent too much time in sluggish UEFI menus?
It depends. Setting jack to frame size 64 or lower has in my
experience shown xruns with frequency switching. This includes Intel's
"Boost" setting which is not turned off by setting performance. There
seems to be no problem when the speed goes up but I often see an xrun
when the speed goes down (just at speed change).
However, Intel has been doing speed switching in the CPU for a while
now and we are still able to set a steady speed with that on the fly.
So with the AMD it may be similar. It may still be possible to set an
upper and lower speed limit. What they do not say, is that the
advertized speed may not be usable in steady state. With the Intel,
the advertized speed can be set for all cores and run that way at 100%
core use and run forever without over heating. AMD tends to advertize
a cpu speed based on some cores running slower and the cpu managing
heat by slowing some cores down. In this case one will have to
experiment to find out what speed can be safely run on all cores
without over heating and use that speed for audio. Hopefully this can
be set on the fly.
Intel doesn't run at top speed "forever". Fastest clock I've got from my
nominal 5GHz-max i9 in my Dell XPS 15 is 4.7GHz. Intel runs clock speed
until thermals say "Slow down." If you're talking about a laptop, the
specific laptop's ability to dissipate heat is the controlling factor.
I'm not sure that Intel thermal control is anywhere within reach of BIOS
and OS software.
Another comment of "blowing loads of energy" with performance mode. It
was actually found that the old "ondemand" governor actually used more
power than "performance" in many cases. Ondemand has to wake up every
once in a while to see what is happening, but in performance mode the
core can go to an idle state. The newer intel powersave mode does not
have this problem but AMD (although they started work on their own
governor for linux) can only use ondemand.
The easiest way to see power use is to watch core temperature... all
power used ends up as heat.
It and clock are good indicators.
--
David W. Jones
gnome@xxxxxxxxxxxxx
authenticity, honesty, community
http://dancingtreefrog.com
"My password is the last 8 digits of π."
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