How hard would it be to build a low-latency kernel for PowerPC (g4)? I haven't build a kernel for 10 years.
Last year I was using this PowerMac g4 to record audio with 12.04. I could never get it to record at 192 KHz (my post from last year: http://ubuntuforums.org/showthread.php?t=2085988). I did find that it would record at 176 KHz fairly reliably, only getting an overrun every now and then.
A few weeks ago, I had a brain cramp and decided to upgrade it to a newer release (this turned out to be a case of "if it ain't broke don't fix it"). But I upgraded it all the way to 13.10 and then discovered it will no longer record reliably record at 176 KHz, it gets overruns every few seconds. I tried the kernels from 12.10 (3.5.0-43), 13.04 (3.8.0-17), and 13.10 (3.11.0-3) and all of the kernels after 12.04 are nasty as far as overruns go, getting 5 or 6 overruns in less than 3 minutes of recording.
I re-installed 12.04 in a different partition and it was better, only getting one overrun in about 3 minutes of recording. Which is still worse than I remember it being last year, when it would usually record 10 or 15 minutes before getting an overrun. I disabled Xorg and found that it would record without an overrun, but the audio had pops and clicks in it anyway.
I then installed Ubuntu-server 12.10 in another partition to see if having minimal stuff running would improve it, but the overruns are still very bad and happen every few seconds.
The hardware has not been changed since last year, so I am assuming this must be caused by software?
I have also observed on both the PowerPC machines I have strange pauses that I don't see on any of the x86 machines I have. Like sometimes while typing on the command line there is 2 or 3 second pause between typing a character and it appearing on the screen. And when the desktop is running, I often click on something and there is a delay of several seconds before anything happens. I was telling my son about it a few days ago and he said that when he had some PowerPC machines years ago, he saw the same thing. I believe he said he saw it on G5 machines.
Is it possible to build a low latency kernel for PowerPC, or is there some other issue that is causing this?