Part II: Running SMP kernel but only one cpu

Tim Judd tajudd at
Tue May 5 06:00:09 UTC 2009

On Mon, May 4, 2009 at 11:49 PM, Duane <duane at> wrote:

> On 5/4/09, Tim Judd <tajudd at> wrote:
> > IRQ15 is typically your secondary IDE controller; but due to PCI (or
> E-ISA)
> > plug&play, including the PnP the BIOS may setup, lots of others can be on
> > that bus too.
> This box has one SCSI card running two SCSI drives. The IDE's are
> disabled in the BIOS. But the SCSI card does feature in the problem:
> >   # grep -i irq15 /var/run/dmesg.boot
> No 'irq15' is found. One can see that the "interrupt storm" begins
> when the SCSI drives begin to spin up, IF the machine is booting with
> two cpus initialized. dmesg.boot is attached for everyone's
> edification and amusement!
> Another interesting datapoint is that if the machine is booted in Safe
> Mode the "interrupt storm" disappears, but  so does the second cpu.
> Best regards,
> --
> Duane

I've seen the IRQ storms when an IDE channel is disabled too.  And to
silence it I had to enable the channel (using an IRQ), with no devices on
it.  it's gonna be a chatterbox, and the question is if the system can work
with a shortage of up to 2 IRQs (irq 14 = primary IDE, irq 15 = secondary

Especially early 586 and 686 classes I saw that often.

Would you try enabling the IDE channels and see if the IRQ storms stop?


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