RE: spurious 8259A interrupt

[Maciej W. Rozycki]

On Tue, 23 Mar 2004, Guennadi Liakhovetski wrote:

> Yes, I saw this your explanation. Thanks again. But, I am not getting
> those errors with local APIC disabled. That's why I thought "local APIC ->

 Is the local APIC normally disabled, i.e. do you see a message like: 
"Local APIC disabled by BIOS -- reenabling." when you boot with your local 
APIC enabled?  That might explain the difference.

> timer -> spurious interrupts." Maybe I am wrong. But I also can't see how
> enabling the lapic can cause, e.g., power supply glitches to become
> visible. I would be happy and grateful to hear an explanation.

 I don't know what setup you are useing, but depending on the
implementation, the local APIC may treat ExtINTA interrupts as
level-triggered or as edge-triggered.  The latter setup is a design error
in my opinion (the 8259A has a level-triggered output) and may lead to
what you observe.  As the local APIC latches edge-triggered interrupts it 
receives (unlike the 8259A) a glitch on an interrupt line does not have to 
last long enough for a CPU to accept it for a spurious interrupt to be 
recorded.

-- 
+  Maciej W. Rozycki, Technical University of Gdansk, Poland   +
+--------------------------------------------------------------+
+        e-mail: macro@xxxxxxxxxxxxx, PGP key available        +
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