sharing irq apic irqs

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From - Wed Nov  8 20:24:25 2000
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From: Robert Lipe <robertlipe@usa.net>
Newsgroups: comp.unix.sco.misc
Subject: Re: IRQ Problem
Date: Wed, 08 Nov 2000 14:47:20 -0000
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"Filip Verborgh" <filip.verborgh@tijd.com> writes:

>Hello,

>I have a Dual Processor HP Netserver LC2 with HP Netraid controller running
>SCO Openserver 5.0.5
>In this server are two HP (D5013A) Network Cards installed.
>The hardware configuration (hwconfig -hc) from SCO reports that the two NICs
>are on IRQ-Vector 16 and 17 (See futher - lines hptx0 & hptx1)
>How is this possible?

MP systems, built on the premise that you don't mind spending an
additional $0.42[1] for the performance you gain by NOT sharing interrupts,
use a more modern interrupt controller than the cascaded 1970's era
parts that are used in commodity-grade UP systems.  This is called the
Advanced Programmable Interrupt Controller (APIC) and allows every slot
(indeed, every function on every slot, I believe) to have its own IRQ.


>Are there any known problems with this strange configuration (at first sight
>everything works just fine) ?

No.   This is a Good Thing.

>How can I change these IRQ-Vectors to a normal situation between 1 and 15
>(eg IRQ3 and IRQ10)?

You could presumably disable APIC support (usually in the BIOS setup)
and live with the resulting performance penalty of dumbing down your
hardware if you really have burning desires to do so.

RJL

[1] OK, I don't know what the cost really is, but it can't be much in 
    the grand scheme of things.

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