On 2/18/19 6:10 AM, Len Ovens wrote:
On Sun, 17 Feb 2019, david wrote:
On 2/17/19 1:01 PM, Len Ovens wrote:
- no hyperthread
- etc.
Yet on my i7 laptop, audio works with hyperthreading just fine.
My experience is that HT is ok at 64/2 but starts to have problems at
lower latency. This doesn't matter for most recording where the audio
can be run at 1024/2 but when using the computer as a live synth or
guitar effects unit, it matters. My general thought is that if something
matters at a lower latency... sooner or later it will bite with a
"stray" xrun even at a higher latency.
Can't do 64/2 with my USB card. 512/3 on a non-RT kernel runs at 10.7ms
with no xruns.
It is in performance mode, though. I think keeping a steady clock is
more important for RT audio than the number of threads.
In recent intel chips with "Boost",
Mine is old enough it has no Boost settings of any sort. Can't be
overclocked, either. Runs at 2.4GHz max. Under heavy loads - not when
doing audio stuff, but when stitching big panoramas - it heats up a lot.
Performance mode means set the cpu
speed to rated speed. However, at higher cpu use the speed will still go
up and down between the limmits of rated speed and max boost speed.
Going up does not seem to be a problem, but going down does. Also, Boost
is temperature controlled... this means that the cpu is running closer
to the maximum temperature and if it gets too close the speed will go
below rated speed to cool down. Temperature control uses cpu time... but
the code is not controlled by the OS and over temperature events tend to
do bad things to audio.
I think temperature is the biggest performance problem on laptops.
So it is worth turning Boost off to give a
steady clock frequency. (I have in the past found that setting speed to
800Mhz does better audio than "ondemand" at 1.6Ghz) By watching
temperatures while running the cpu(s) at 100% (build Ardour for example)
I have found that I could actually run at a higher speed than
preformance by setting min/max speeds rither than a governor. However, I
don't do this because I know that things like dust and wearing fans will
change this over time and rated speed does give some headroom.
Anyway, I set jack to 16/2 and tweak for (hopefully) no xruns or best
case. Then I am pretty sure I have done the best I can do at higher
latency. (I turn cron off too while recording) I have a PCI audio
device, USB devices will not do 16/2... 16/3 maybe, probably 32/* is a
better target for USB.
Thanks, will keep that in mind. I have a Presonus Firewire card around
that I'd like to connect into the setup. (My old laptop had a Firewire
port.)
My good old reliable motherboard in my desktop machine decided that
being six years old meant it was time for the onboard video to die. I
was using the onboard video because the added video card had also died a
few years ago. (I also switched to a KVM that used USB connections, and
the old BIOS in the machine only recognizes keyboards plugged into the
PS/2 port.) So I'm looking into Ryzen 2700x/mobo/memory combos while the
desktop machine now does reliable work with a 3GHz Pentium.
--
David W. Jones
gnome@xxxxxxxxxxxxx
authenticity, honesty, community
http://dancingtreefrog.com
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