Dell Inspiron 2600: Sound output slowed when using vchannels

[Mark J. Miller]

Hi,

I just tried adding some virtual channels to my laptop to get XMMS and
KDE's sound server to play nicely using the commands:

sysctl hw.snd.pcm0.vchans=4
sysctl hw.snd.maxautovchans=4

As soon as I play the next mp3, even with XMMS still pointing at
/dev/dsp0, Liz Phair starts sounding like she's tired and has a cold.
Timing it, it seems like each track takes an extra 5 seconds per minute of
play.  Setting the number of vchannels to 1 doesn't fix things, but
setting it back to 0 restores things to perfect playback.  This is very
repeatable.  The hardware is the Inspiron 2600's builtin soundcard.
Here's the output of dmesg:

Copyright (c) 1992-2003 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 4.8-STABLE #0: Wed Jun 18 22:43:27 PDT 2003
    mjm at zoe.verizon.net:/usr/obj/usr/src/sys/ZOE.5
Timecounter "i8254"  frequency 1193182 Hz
CPU: Mobile Intel(R) Pentium(R) 4 - M CPU 1.70GHz (1695.01-MHz 686-class
CPU)
  Origin = "GenuineIntel"  Id = 0xf27  Stepping = 7

Features=0xbfebf9ff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
real memory  = 133693440 (130560K bytes)
avail memory = 123301888 (120412K bytes)
Preloaded elf kernel "kernel" at 0xc068c000.
Preloaded elf module "linux.ko" at 0xc068c09c.
Preloaded elf module "nvidia.ko" at 0xc068c13c.
Pentium Pro MTRR support enabled
md0: Malloc disk
Using $PIR table, 8 entries at 0xc00fdf40
apm0: <APM BIOS> on motherboard
apm0: found APM BIOS v1.2, connected at v1.2
npx0: <math processor> on motherboard
npx0: INT 16 interface
pcib0: <Intel 82845 Host to PCI bridge> on motherboard
pci0: <PCI bus> on pcib0
agp0: <Intel 82845 host to AGP bridge> mem 0xec000000-0xefffffff at device
0.0 on pci0
pcib1: <Intel 82845 PCI-PCI (AGP) bridge> at device 1.0 on pci0
pci1: <PCI bus> on pcib1
nvidia0: <GeForce2 Go> mem 0xf0000000-0xf7ffffff,0xe0000000-0xe0ffffff irq
10 at device 0.0 on pci1
uhci0: <Intel 82801CA/CAM (ICH3) USB controller USB-A> port 0x1800-0x181f
irq 10 at device 29.0 on pci0
usb0: <Intel 82801CA/CAM (ICH3) USB controller USB-A> on uhci0
usb0: USB revision 1.0
uhub0: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
uhci1: <Intel 82801CA/CAM (ICH3) USB controller USB-B> port 0x1820-0x183f
irq 11 at device 29.1 on pci0
usb1: <Intel 82801CA/CAM (ICH3) USB controller USB-B> on uhci1
usb1: USB revision 1.0
uhub1: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub1: 2 ports with 2 removable, self powered
pcib2: <PCI to PCI bridge (vendor=8086 device=2448)> at device 30.0 on
pci0
pci2: <PCI bus> on pcib2
xl0: <3Com 3c905C-TX Fast Etherlink XL> port 0x3000-0x307f mem
0xe8000000-0xe800007f irq 10 at device 1.0 on pci2
xl0: Ethernet address: 00:08:74:e5:ff:7c
miibus0: <MII bus> on xl0
ukphy0: <Generic IEEE 802.3u media interface> on miibus0
ukphy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, auto
pcic0: <O2micro 6912 PCI-Cardbus Bridge> irq 10 at device 4.0 on pci2
pcic0: PCI Memory allocated: 0x88000000
pcic0: Warning: O2micro OZ68xx chips may not work
pccard0: <PC Card 16-bit bus (classic)> on pcic0
isab0: <PCI to ISA bridge (vendor=8086 device=248c)> at device 31.0 on
pci0
isa0: <ISA bus> on isab0
atapci0: <Intel ICH3 ATA100 controller> port
0x1840-0x184f,0-0x3,0-0x7,0-0x3,0-0x7 at device 31.1 on pci0
ata0: at 0x1f0 irq 14 on atapci0
ata1: at 0x170 irq 15 on atapci0
pci0: <unknown card> (vendor=0x8086, dev=0x2483) at 31.3 irq 10
pcm0: <Intel 82801CA (ICH3)> port 0x1880-0x18bf,0x1c00-0x1cff irq 10 at
device 31.5 on pci0
pcm0: <SigmaTel STAC9700/9783/9784 ac97 codec>
pci0: <unknown card> (vendor=0x8086, dev=0x2486) at 31.6 irq 10
orm0: <Option ROMs> at iomem
0xc0000-0xcdfff,0xce000-0xce7ff,0xdc000-0xdffff on isa0
fdc0: <NEC 72065B or clone> at port 0x3f0-0x3f5,0x3f7 irq 6 drq 2 on isa0
fdc0: FIFO enabled, 8 bytes threshold
fd0: <1440-KB 3.5" drive> on fdc0 drive 0
atkbdc0: <Keyboard controller (i8042)> at port 0x60,0x64 on isa0
atkbd0: <AT Keyboard> flags 0x1 irq 1 on atkbdc0
kbd0 at atkbd0
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: model Generic PS/2 mouse, device ID 0
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
sio0: configured irq 4 not in bitmap of probed irqs 0
sio0 at port 0x3f8-0x3ff irq 4 flags 0x10 on isa0
sio0: type 8250
sio1: configured irq 3 not in bitmap of probed irqs 0
ppc0: <Parallel port> at port 0x378-0x37f irq 7 on isa0
ppc0: Generic chipset (ECP/PS2/NIBBLE) in COMPATIBLE mode
ppc0: FIFO with 1/0/0 bytes threshold
plip0: <PLIP network interface> on ppbus0
lpt0: <Printer> on ppbus0
lpt0: Interrupt-driven port
ppi0: <Parallel I/O> on ppbus0
ad0: 19077MB <IC25N020ATCS04-0> [38760/16/63] at ata0-master UDMA100
acd0: CD-RW <TEAC CD-RW CD-W224E> at ata1-master PIO4
Mounting root from ufs:/dev/ad0s3a

Thanks in advance for any help,
Mark