What am I losing with noapic

[Tim Kay]

Hi all,
	Does anyone know what I'm actually losing with having to set noapic on 
bootup? I mean in real terms how much harder / slower is an SMP machine 
working when it's doing standard multi-bus xt polling compared to when it's 
in APIC poll state. I appreciate that there can be a reduction in interrupt 
response latency using the damn thing but is this a measurable amount given a 
machine processing about 1200 interrupts/sec? (this figure is a sum rather 
than per processor). As an added complication how do I get around interrupt 
routing conflicts in noapic mode and do the 'routing conflict for xx:xx:xx 
have X want Y' messages make any difference to this performance?

	A useful URL (I couldn't find any) or reference would suffice if this is too 
invloved or boring a topic to explain easily.

TIA

Tim

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Tim Kay
systems administrator
Advfn.com Plc - http://www.advfn.com/