So I had an old netbook that I had running with Ubuntu 11.10 that I "upgraded" with the Studio packages (it's old enough that it doesn't have a DVD-ROM). I could get a latency of around 8ms through Jack with it. Sadly, it won't stay running for more than about 30 seconds now due to a power supply issue (I think).
So because the netbook is dying a horrible death, I took the opportunity to buy my wife a new computer and confiscated hers. It's a Dell Studio 1737, and it has what I've been wanting in my audio rig for a while...a Firewire port. I've got a Presonus Firebox that's been collecting dust for about 3 years waiting for me to use it. This PC is superior in literally every single way when it comes to hardware.
So here's the problem...fresh install of 11.10 UbuntuStudio 64-bit. I've set the IRQ priorities for Yenta and Firewire, I THINK I've shut off CPU freq scaling (I have my doubts..is there a decent way to tell? everything I find for this is for 10.04 or earlier...). The best I can get for latency is about 17ms, which is awful for me. It doesn't matter if it's the on-board audio (Intel ICH9) or the Firebox, it's all about 17ms...which makes me think something else is going on.
What's interesting is that with just UbuntuStudio and updates with the standard repositories, I get an xrun callback every 5 seconds exactly when I try lower latencies, but I also get D-BUS errors every time I try to stop Jack (and it dies a horrible, painful death). I read a forum post talking about KX Studio, so I added their repositories, and now it's about every 8 seconds, and PulseAudio throws errors about not running (my wife has heard "@&*@$%! !$%%$@*& PULSE AUDIO @#%^%^!$!!!!!" more times than I think I care to count)...but the D-BUS errors are gone and Jack at least shuts down nicely. Still, the best I can do for latency is around 17ms.
I've now been working on this for every waking moment for about 3 days (including temporarily loading Windoze back on it so that I could update the BIOS) and I'm at my wit's end. Anybody have any ideas?