It appears that the latest BIOS version 1805 for the ASUS A8N-SLI Deluxe
board fixes the broken ACPI timer override that was in earlier versions,
and which the kernel ignores on nForce4 chipsets. Now the same override:

ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)

seems to be needed, since without acpi_use_timer_override we end up
getting this (with apic=verbose):

..TIMER: vector=0x30 apic1=0 pin1=0 apic2=-1 pin2=-1
..MP-BIOS bug: 8254 timer not connected to IO-APIC
...trying to set up timer (IRQ0) through the 8259A ...  failed.
...trying to set up timer as Virtual Wire IRQ... failed.
...trying to set up timer as ExtINT IRQ... works.

and the timer IRQ ends up routed as XT-PIC instead of IO-APIC-edge. With 
acpi_use_timer_override we just get:

..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1

and it works through the IO-APIC.

I should think there must be a better way to handle this automatically.. 
Is there some way we can tell, given we have a chipset with a 
potentially broken BIOS, from the configuration of the IOAPIC whether 
the timer override is needed or not? Unfortunately I don't have output 
from apic=verbose with the old BIOS with the broken override, but maybe 
somebody else can provide that..

Attached are boot logs from 2.6.22-rc6-mm1 with and without 
acpi_use_timer_override along with the diff between them. Oddly enough, 
2.6.23-rc1-mm2 without acpi_use_timer_override spewed a warning about 
check_irq_resend and then paniced on boot since all attempts to set up 
the timer failed, but only when apic=verbose was set. Some kind of 
timing thing perhaps?

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/