[linux-audio-user] Ardour, Jack, and 2.6 kernels + XRuns with the Audiophile 24/96 M-Audio

[Joel White]

Aha, a thread convergence!

I started the "Ardour..." thread lamenting long xruns under the 2.6 
kernels.  Based on recommendations on the list, I went back to a 2.4 
kernel, still having the occasional long xrun.  In the "XRuns..." 
thread, the following from a post by Jan Depner caught my eye:

"What kind of disk drives? Adaptec SCSI controllers can give you 
problems with xruns."

Uh-oh.  I'm using an Adaptec controller on my main board (a 7890).  With 
a little digging, I came up with the following from the ST Audio website 
(http://www.staudio.de/kb/english/conflicts/):

"The famous Adaptec 2940 SCSI controller series is causing performance 
problems when installed in the same system as our DSP24 series and when 
the audiodata is stored on a SCSI-HDD connected to the controller. To 
get good results in benchmark tests, the Adaptec controller keeps steady 
access to the PCI bus. The result is a reduction of data transfer of 
other PCI cards like the DSP24 hardware. This means that the ASIO/MME 
buffer size (which is the latency) needs to be set to a relative high 
value to avoid stuttered audio playback and drop-outs during recording. 
The performance problems can be reduced if both the DSP24 and the 
Adaptec controller both have a unique and unshared IRQ. Still the 
performance will not be as good compared to the regular onboard 
IDE-controller of a modern mainboard. This means that the best solution 
is to use a IDE-HDD to save the audiodata from within your recording 
software. The simple presence of the controller (that is used while the 
audiodata is stored on a IDE-HDD) is no problem."

Uh-oh again.  The 7890 is the on-board version of the 2940.  I thought I 
had the xruns pretty much under control with the 2.4 kernel, then I 
picked up a M-Audio Delta 1010LT (I was jonesing for the 8 channels of 
input!).  Ugh.  I can't record more than a few seconds of 8 channel 
input before a 100msec+ xruns brings everything to a halt.  Even 
recording 2 channels won't make it through a 4:00 min song.

So, am I completely hosed with my Adaptec SCSI drive setup?  Anybody 
have any insight into these Adaptec controllers?  I've fussed with the 
setpci latency_timer settings (from Jan Depner's "Installing and 
configuring ALSA, JACK, & Ardour..." web site), but still see long 
xruns.  Trying an IDE drive is not that simple, as I don't have any 
drive slots left in the box (I've got 4 SCSI drives setup as a RAID).  
So, I'd like to exhaust all possibilities before trying new drive 
configurations.

Any thoughts/ideas/suggestions would be _greatly_ appreciated!

Thanks,

Joel