[LAU] xruns with Delta 66 on F7/Planet CCRMA

I sent this message to the Planet CCRMA list, but got no response. Maybe someone here has some suggestions? I've been running Planet CCRMA for years and have generally been happy with it. Since moving to Fedora 7, however, I can't get my jack latency settings as low as I'd like. I get periodic xruns (without any jack apps running) at anything below 1024 frames and 2 periods. The hardware is an Athlon 1800, 1G RAM, with a M-Audio Delta 66. Same hardware I've had for years, and I could swear I had better performance with FC5 (and FC2, and RH9). I've looked at everything I can think of: I've got the latest Planet kernel: paul@boon ~]$ uname -r 2.6.22.6-1.rt9.5.fc7.ccrmart I bumped the PCI latency timer up on the ICE1712 chip (the Delta): 00:0a.0 Multimedia audio controller: VIA Technologies Inc. ICE1712 [Envy24] PCI Multi-Channel I/O Controller (rev 02) Subsystem: VIA Technologies Inc. M-Audio Delta 66 Flags: bus master, medium devsel, latency 248, IRQ 20 IRQ stuff looks fine to me (audio on IRQ 20): [paul@boon ~]$ cat /proc/interrupts CPU0 0: 272253996 IO-APIC-edge timer 1: 2 IO-APIC-edge i8042 6: 6 IO-APIC-edge floppy 7: 0 IO-APIC-edge parport0 8: 0 IO-APIC-edge rtc0 9: 0 IO-APIC-fasteoi acpi 12: 4 IO-APIC-edge i8042 14: 893299 IO-APIC-edge libata 15: 5410951 IO-APIC-edge libata 16: 1602810 IO-APIC-fasteoi uhci_hcd:usb1, uhci_hcd:usb2, uhci_hcd:usb3, ehci_hcd:usb4 18: 2 IO-APIC-fasteoi ohci1394 19: 1374546 IO-APIC-fasteoi eth0 20: 3078836 IO-APIC-fasteoi ICE1712 NMI: 0 LOC: 319262183 ERR: 0 MIS: 0 The only IRQ with a higher priority is the RTC on 8 (seems sensible): [paul@boon ~]$ ps -e -o pid,cmd,pri | grep IRQ 61 [IRQ-9] 90 304 [IRQ-12] 104 305 [IRQ-1] 105 322 [IRQ-16] 110 345 [IRQ-14] 90 346 [IRQ-15] 90 673 [IRQ-6] 90 910 [IRQ-8] 120 942 [IRQ-18] 90 948 [IRQ-7] 90 1034 [IRQ-20] 115 1498 [IRQ-19] 90 Jackd priority looks right (I assume the 100 is the watchdog, 90 is the audio thread?): [paul@boon ~]$ ps -mo pid,cmd,pri -C jackd PID CMD PRI 31851 jackd -R -P50 -dalsa -dhw:0 - - - 19 - - 19 - - 19 - - 100 - - 90 QJackctl is using this: [paul@boon ~]$ cat .jackdrc jackd -R -P50 -dalsa -dhw:0 -r44100 -p256 -n2 And yet, xruns: 21:40:37.506 Startup script... 21:40:37.512 artsshell -q terminate JACK tmpdir identified as [/dev/shm] 21:40:37.877 Startup script terminated with exit status=256. 21:40:37.879 JACK is starting... 21:40:37.884 jackd -R -P50 -dalsa -dhw:0 -r44100 -p256 -n2 21:40:37.903 JACK was started with PID=32405 (0x7e95). jackd 0.103.0 Copyright 2001-2005 Paul Davis and others. jackd comes with ABSOLUTELY NO WARRANTY This is free software, and you are welcome to redistribute it under certain conditions; see the file COPYING for details JACK compiled with System V SHM support. loading driver .. Enhanced3DNow! detected apparent rate = 44100 creating alsa driver ... hw:0|hw:0|256|2|44100|0|0|nomon|swmeter|-|32bit control device hw:0 configuring for 44100Hz, period = 256 frames, buffer = 2 periods ALSA: final selected sample format for capture: 32bit little-endian ALSA: use 2 periods for capture ALSA: final selected sample format for playback: 32bit little-endian ALSA: use 2 periods for playback 21:40:40.166 Server configuration saved to "/home/paul/.jackdrc". 21:40:40.168 Statistics reset. 21:40:40.169 Client activated. 21:40:40.171 Audio connection change. 21:40:40.199 Audio connection graph change. JACK tmpdir identified as [/dev/shm] Enhanced3DNow! detected 21:40:40.374 Audio active patchbay scan... 21:41:11.971 XRUN callback (1). delay of 11622.000 usecs exceeds estimated spare time of 5619.000; restart ... **** alsa_pcm: xrun of at least 0.054 msecs 21:41:21.684 XRUN callback (2). Any help would be appreciated. What have I missed?