Reading error logs should be part of our regular routine (just as you would under Windows). After a preliminary install you should check all your /var/logs to further fine tune your Ubuntu system
go to /var/log
open up the kernel log, kern.log. scroll through it.
This exercise is to sjhow what you would do to try to ascertain a problem as it relates to an IRQ 185 problem and trying to identify what devices are likely suspects which are causing said problem.
Search for the IRQ map
[color=blue]Using vector-based indexing
localhost kernel: IRQ to pin mappings:
localhost kernel: IRQ0 -> 0:2
localhost kernel: IRQ1 -> 0:1
localhost kernel: IRQ3 -> 0:3
localhost kernel: IRQ4 -> 0:4
localhost kernel: IRQ5 -> 0:5
localhost kernel: IRQ6 -> 0:6
localhost kernel: IRQ7 -> 0:7
localhost kernel: IRQ8 -> 0:8
localhost kernel: IRQ9 -> 0:9
localhost kernel: IRQ10 -> 0:10
localhost kernel: IRQ11 -> 0:11
localhost kernel: IRQ12 -> 0:12
localhost kernel: IRQ13 -> 0:13
localhost kernel: IRQ14 -> 0:14
localhost kernel: IRQ15 -> 0:15
localhost kernel: IRQ169 -> 0:16
localhost kernel: IRQ201 -> 0:17
localhost kernel: [/color][color=red]IRQ185 -> 0:18[/color][color=blue]
localhost kernel: IRQ177 -> 0:19
localhost kernel: IRQ193 -> 0:23[/color]
it should say somewhere else:
[COLOR=Blue]PCI: Using ACPI for IRQ routing
IRQ185 -> 0:18[/COLOR] scroll through it some more.
you should find a line that looks like this:
[COLOR=Blue]**ACPI**: PCI interrupt 0000:[/color][color=red]00:1f.1[/color][color=blue][A] -> GSI 18 (level, low) -> **IRQ 185**[/COLOR]
So, this is telling me that IRQ 185 is associated with ACPI.
But wait, there's more:
[COLOR=Blue]APCI: PCI interrupt 0000:[/color][color=red]00:1d.2[/color][color=blue][C] -> GSI 18 (level, low) -> **IRQ 185**
ACPI: PCI interrupt 0000:[/color][color=red]02:01.0[/color][color=blue][A] -> GSI 18 (level, low) -> **IRQ 185**
ACPI: PCI interrupt 0000:[/color][color=red]03:03.2[/color][color=blue][ B ] -> GSI 18 (level, low) -> **IRQ 185**
[/COLOR]
Notice how they are all at GSI level 18?
So let's look for all the lines that end with "IRQ 185"...
scroll some more and you should see something like this:
[COLOR=Blue]ACPI: PCI interrupt 0000:00:_1d.2_[C] -> GSI 18 (level, low) -> **IRQ 185**
uhci_hcd 0000:[/color][color=red]00:1d.2[/color]: [COLOR=darkgreen]Intel Corp. 82801EB/ER (ICH5/ICH5R) USB UHCI[/COLOR] [color=blue]#3
PCI: Setting latency timer of device 0000:00:1d.2 to 64
uhci_hcd 0000:[/color][color=red]00:1d.2[/color][color=blue]: irq 185[/U], io base 0000e800
uhci_hcd 0000:00:1d.2: _new USB bus registered_, assigned bus number 3
hub 3-0:1.0: _USB hub found_
hub 3-0:1.0: _2 ports detected_
usb 2-2: new low speed USB device using address 2[/COLOR]
Scroll down some more. You may see something like this:
[COLOR=Blue]ACPI: PCI interrupt 0000:[/color][color=red]02:01.0[/color][color=blue][A] -> GSI 18 (level, low) -> **IRQ 185**
PCI: Setting latency timer of device 0000:02:01.0 to 64
e1000: eth0: e1000_probe: [/color][color=darkgreen]Intel(R) PRO/1000 Network Connection[/COLOR]
but wait, there's more:
[COLOR=Blue]ieee1394: Initialized config rom entry `ip1394'
ohci1394: $Rev: 1223 $ Ben Collins <bcollins@debian.org>
ACPI: PCI interrupt 0000:[/color][color=red]03:03.2[/color][color=blue][ B ] -> GSI 18 (level, low) -> **IRQ 185**
ohci1394: fw-host0: [/color][color=darkgreen]OHCI-1394 1.1[/color][color=blue] (PCI): IRQ=[185][/U] MMIO=[ff904000-ff9047ff] Max Packet=[2048]
ieee1394: Host added: ID:BUS[0-00:1023] GUID[00023c00200021ea]
e1000: eth0: e1000_watchdog: NIC Link is Up 100 Mbps Full Duplex[/COLOR]
So, not only do I have a USB hub on software IRQ 185, but I also have my NIC card and firewire. All the devices are controlled by ACPI (like "wake-on-lan", "wake-on-mouse-movement", disk cycle down, etc).
Now, remember that first line we looked at, that "00:1f.1"?
[COLOR=Blue]PCI: Ignoring BAR0-3 of _IDE controller_ 0000:00:1f.1
ACPI: PCI interrupt 0000:[/color][color=red]00:1f.1[/color][color=blue][A] -> GSI 18 (level, low) -> **IRQ 185**
**ICH5**: [/color][color=darkgreen]IDE controller[/color][color=blue] at PCI slot 0000:[/color][color=red]00:1f.1[/color][color=blue]
PCI: Enabling device 0000:00:1f.1 (0005 -> 0007)[/COLOR]
You should also see this, somewhere:
[color=blue]ACPI: (supports S0 S1 S4 S5)
ACPI wakeup devices:
TANA P0P3 AC97 USB0 USB1 USB2 USB3 USB7 SLPB[/color]
So, we end up with this as a device map:[size=3]
ACPI: PCI interrupt 0000:00:1f.1 IRQ 185 [COLOR=Red]ICH5 IDE Disk Controller[/COLOR]
APCI: PCI interrupt 0000:00:1d.2 IRQ 185 [COLOR=blue]USB Hub[/COLOR]
ACPI: PCI interrupt 0000:02:01.0 IRQ 185 [COLOR=darkred]Intel Pro 1000 NIC[/COLOR]
ACPI: PCI interrupt 0000:03:03.2 IRQ 185 [COLOR=royalblue]1394 Firewire[/COLOR][/SIZE]