Re: Linux interrupt latency

From: Alan Cox (
Date: Tue Feb 06 2001 - 09:15:44 EST

> A 450MHz PII processor isn't really up to the task. Jim Dixon, who
> designed the card, recommends at least a 733MHz PIII, based on his
> experience with the original BSD driver. I am able to run one as a dual

It shouldnt matter. If its entirely tied to ISA bus performance you should
be able to run it on 486 quite honestly.

> card, and about 1/2 the time for a dual E1 card. This really sucks, and
> needs to be addressed when the more serious long term PCI version of the
> card goes through.

or hang a small CPU on it and shove it on USB since USB can do isosynchronous

> > >chipsets, particularly what event might be occuring once per second and
> > >disabling interrupts for a couple of hundred microseconds? Thanks!
> I think you are trying one board that is close to the limit, and one
> just beyond. Simple as that.

And quite a few chipsets steal cycles for other things (memory refresh, ram
thermal limiting and the like). With the Z85230 driver which also at high
speed really tests ISA bus throughput I regularly saw PCI boxes getting
worse performance than ancient all ISA relics. Throughput was also comparable
between a K5 and a PII/233

> Good idea. I'll have to try that. There always seem to be lots of
> problem reports about IOAPIC, though. Should I trust it?

The problems with the IO apic are generally bios, however there is one
concern I have. APIC is a message passing bus so doesnt have a guaranteed
delivery time.

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This archive was generated by hypermail 2b29 : Wed Feb 07 2001 - 21:00:23 EST