Hi Mark :
Ground loop problem? As a test only, what happens if you unplug power
on the printer, or turn the printer off?
Same noise. It stops if I pull either the power or the USB cable.
If it is a ground loop issue - I did hear of this recently with a USB
hard drive I think - then possibly it's a cable issue or maybe you
could stuck a USB hub in the middle to break the loop? (Just
guessing!) ;-)
I tried sticking a hub between the machine and the printer, it didn't
reduce the noise at all. :(
I'm going to visit our brand-new Wal Mart to look for a
noise-suppressive cable.
On the off chance it's something more nefarious, what are the relative
IRQ priorities of the USB controller vs. the sound card? I Assume the
sound card's IRQ has a high realtime priority? If not, and it's lower
than USB, then possibly there is some strange interaction. I've never
run into anything like that with USB, but I have with other devices
like a mouse, etc.
Here's the output from lspci and /proc/interrupts on the offending machine :
Output from lspci:
00:00.0 Host bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133]
(rev 02)
00:01.0 PCI bridge: VIA Technologies, Inc. VT8363/8365 [KT133/KM133 AGP]
00:07.0 ISA bridge: VIA Technologies, Inc. VT82C686 [Apollo Super South]
(rev 22)
00:07.1 IDE interface: VIA Technologies, Inc.
VT82C586A/B/VT82C686/A/B/VT823x/A/C PIPC Bus Master IDE (rev 10)
00:07.2 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 10)
00:07.3 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1
Controller (rev 10)
00:07.4 Bridge: VIA Technologies, Inc. VT82C686 [Apollo Super ACPI] (rev 30)
00:10.0 Ethernet controller: Lite-On Communications Inc LNE100TX
[Linksys EtherFast 10/100] (rev 25)
00:12.0 Multimedia audio controller: Creative Labs SB Live! EMU10k1 (rev 08)
00:12.1 Input device controller: Creative Labs SB Live! MIDI/Game Port
(rev 08)
00:14.0 Multimedia audio controller: VIA Technologies Inc. ICE1712
[Envy24] PCI Multi-Channel I/O Controller (rev 02)
01:00.0 VGA compatible controller: nVidia Corporation NV11 [GeForce2
MX/MX 400] (rev b2)
Output from 'cat /proc/interrupts' :
CPU0
0: 62304648 XT-PIC timer
1: 5639 XT-PIC i8042
2: 0 XT-PIC cascade
3: 127 XT-PIC EMU10K1
5: 9043743 XT-PIC ICE1712, uhci_hcd:usb1, uhci_hcd:usb2
7: 1 XT-PIC parport0
8: 4 XT-PIC rtc
11: 63698 XT-PIC eth0
12: 537858 XT-PIC i8042
14: 46717 XT-PIC ide0
15: 23 XT-PIC ide1
NMI: 0
LOC: 0
ERR: 0
MIS: 0
I'm concerned by the USB and ICE1712 sharing the same IRQ. How do I
reassign the interrupt ?
Best,
dp
