IRQs

[Garrett85]

I'M working my way through Trainsignal's CompTIA Linux + Training course and I have a question about IRQs. According to the lesson using the command "cat /proc/interrupts", I need to memorize the system IRQs number columns 0-15. But when I use this command, I get somewhat of an unordered list, see below.

cat /proc/interrupts
           CPU0       CPU1       
  0:         48          7   IO-APIC-edge      timer
  1:        247        205   IO-APIC-edge      i8042
  8:          0          1   IO-APIC-edge      rtc0
  9:          0          3   IO-APIC-fasteoi   acpi
 12:        241        646   IO-APIC-edge      i8042
 14:          0          0   IO-APIC-edge      pata_atiixp
 15:          0          0   IO-APIC-edge      pata_atiixp
 16:          1      33038   IO-APIC-fasteoi   ohci_hcd:usb3, ohci_hcd:usb4, HDA Intel
 17:       2650        552   IO-APIC-fasteoi   ehci_hcd:usb1
 18:      37541      14907   IO-APIC-fasteoi   ohci_hcd:usb5, ohci_hcd:usb6, radeon, ath
 19:      12061      21248   IO-APIC-fasteoi   ehci_hcd:usb2
 22:      19898       4822   IO-APIC-fasteoi   ahci
 28:          0          0   PCI-MSI-edge      eth0
NMI:          0          0   Non-maskable interrupts
LOC:     320836     334309   Local timer interrupts
SPU:          0          0   Spurious interrupts
PMI:          0          0   Performance monitoring interrupts
PND:          0          0   Performance pending work
RES:     242901     225850   Rescheduling interrupts
CAL:         62         67   Function call interrupts
TLB:       8703       7185   TLB shootdowns
TRM:          0          0   Thermal event interrupts
THR:          0          0   Threshold APIC interrupts
MCE:          0          0   Machine check exceptions
MCP:          7          7   Machine check polls
ERR:          0
MIS:          0

[Nagarjuna]

I believe this could be because your system either has the corresponding hardware disabled or it doesn't exist.

For example, some of the missing IRQs are:

3, 4 - Serial
5 - Parallel port
6 - Floppy disk controller
7 - Parallel port

This hardware usually doesn't exist on modern systems.