[PlanetCCRMA] Wondering about upgrading my CPU

Paul Coccoli pcoccoli at gmail.com
Tue Jun 2 05:30:58 PDT 2009

On Mon, Jun 1, 2009 at 4:03 PM, JOHN LYON <jalyon at shaw.ca> wrote:
> Hi Everybody,
> I've been struggling with recording on Linux for a while now, and at last I seem to be getting close to where I want to be.
> I'm using Fedora core 10, PlanetCCRMA apps, ardour-2.8-1.fc10.i386, ffado-2.0-0.6.rc1.fc10.ccrma.i386
> libffado-2.0-0.6.rc1.fc10.ccrma.i386, a Focusrite 10 26,  qjackctl-0.3.4-1.fc10.i386, jack-audio-connection-kit-1.9.2-2.fc10.ccrma.i386.  I'm using the edge kernel because my motherboard is an ASUS P5QL Pro, which doesn't work with the 2.6.27 kernels.  So far so good.
> My hardware includes the focusrite IO 26 and a Behringer BCF2000 control surface, which is particularly helpful as I am visually impaired and have trouble with the small mouse pointer and the small print used in Ardour.
> My problem is that I'm still getting xruns.  I use the lightweight window manager XFCE, and I shut off network services when I am recording, (NetworkManager, sshd, ntpd, vsftp, httpd, etc.  This all helps; sometimes I can record at pretty low latencies with no xruns.  But not always.
> Oh, here's an example of how I call jackd:
> /usr/bin/pasuspender --s | /usr/bin/jackd -R -P70 -t5000 -dfirewire -r44100 -p128 -n3 &
> Yes, I can set -p higher, but I've experienced xruns recording, say 4 or 5 mics in ardour at even -p512 or -p1024.
> I do understand that there is quite a bit of trial and error involved in trying to find the best settings for jackd, and I've tried many different -p and -n settings to see if I can find some low latency with no xruns.
> My CPU is an inexpensive Pentium D (although I believe it is running at 3 Ghz).  I'm wondering what I can expect if I upgrade to, say, a relatively fast Core 2 duo or a quad core CPU.  Does anyone have information about how this might affect my situation?  My understanding from years back is that the Linux kernel does a good job at taking advantage of multiple CPUs, and presumably, multiple cores, so I am hopeful that a newer, faster CPU might solve my latency and xrun issues.

I really don't think you should get xruns at 1024 frames per period.
I used to record 4 mics on a 1.8 GHz Athlon XP with 1GB RAM with no
xruns.  That was with a PCI card; I'ved never used firewire.

Some other things to look at:  run "/etc/init.d/rtirq status" and
check the rtprio of your firewire chip.  I like to set the rtprio of
jack just below that of my audio device, but above anything else.
Yours is 70, which on my system is the same as one usb port and the
graphics chip.

Use hdparm to make sure your drives are running their best (search for
articles on how to do this).   Although this isn't usually necessary
any more, especially with SATA drives.

You could also check your PCI latency timer values using lspci.  Try
setting the value to the max for your firewire chip.  See

One day I want to write troubleshooting shell script to check all this stuff.

Maybe the ffado project has more info?  Maybe you have a crappy
firewire chipset?

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