[Asterisk-Users] Intel Desktop MotherBoards Unsuitable for Digium Boards

[Andrew Kohlsmith]

On Tuesday 08 November 2005 18:20, George Pajari wrote:
> To make a long story short, according to Intel Dealer Technical Support
> (we became Intel dealers in order to get answers to our questions) there
> is no Intel motherboard that permits the IRQs to be configured uniquely.
> They are all hardwired and shared. This information applies to both the
> Intel Desktop Board and Server Board product lines.

I find this almost impossible to believe.

In XT-PIC mode, absolutely.  However every modern chipset utilizes an IOAPIC 
now and every device has its own IRQ line.  When the IOAPIC is in emulation 
(XT-PIC) mode, then yes many of the interrupts get "merged" into the standard 
16 interrupts.

However, if your Linux kernel is utilizing the IOAPIC's native mode things 
change drastically:

# cat /proc/interrupts
           CPU0
  0:  942314955    IO-APIC-edge  timer
  1:         10    IO-APIC-edge  i8042
  8:          1    IO-APIC-edge  rtc
  9:          0   IO-APIC-level  acpi
 12:        111    IO-APIC-edge  i8042
 14:     496236    IO-APIC-edge  ide0
177:  211098355   IO-APIC-level  eth0
185:          2   IO-APIC-level  ehci_hcd:usb1
193:          0   IO-APIC-level  ohci_hcd:usb2
201:          0   IO-APIC-level  ohci_hcd:usb3
209:         86   IO-APIC-level  ohci_hcd:usb4
217: 3769265646   IO-APIC-level  wct4xxp

As you can see on this particular system (not an Intel reference board, 
granted, but my Intel boards do work similarly) everything is on its own 
interrupt, and the interrupt numbers don't stop at 15.

I'd really like some clarification on that...  Do Intel reference boards 
actually tie the physical INT# signals of peripherals together, or are they 
just stating that unless you use the native IO-APIC mode you will have shared 
interrupts due to the "emulation"?

Hopefully someone from Digium will step in and give the official word, because 
I have it on good authority that Digium hardware on Intel motherboards work 
well together.  Hell, I've had my old P4 Intel reference board (with RamBus 
memory) work just fine without shared interrupts.

-A.