[plug] eth0 and ppp

[Jon L. Miller]

I'm wondering if what Len meant was that irq 9 cascades irq 2, because of
this we are told to stay away if possible from irq 9 especially when
using nics. Mainly because it can be sporadic.
See : http://www.gerbervm.com/support/fastfacts/3023.htm 

Jon

*********** REPLY SEPARATOR ***********

On 10/13/99, at 4:07 PM, Garth Atkinson  wrote: 

>russ wrote:
>> 
>> Len Bird wrote:
>> > The interrupt trap is usually overlooked by the gurus! I am really a
novice
>> > in Linux but suggest that you boot up in humble old dos for which
there are
>> > a number of programs like FINDIRQ, CHECKIT and others which will
identify
>> > which hardware item is using which Interrupt, and which are unused.
INT 9 is
>> > paired with INT 2 which therefore needs watching. Most Ethernet
Cards these
>> > days are software configured, but you may quite well have a
Jumper-link IRQ
>> > selection. It is usually easier to change the IRQ for the Ethernet
Card than
>> > for the Com Port. If you are stuck for one of these, I can help.
>> >
>> > If you are now sure that IRQ conflict  is the problem, perhaps some
of the
>> > more knowledgeable of the PLUG subscribers can better advise you,
>> 
>> I'm pretty sure that's the problem. The pcmcia finds both cards and
>> assigns IRQ3 to the ethernet card and 9 to the serial card. There are
>> no jumpers on the pcmcia cards. I tried forcing the interrupt for the
>> card to 9 using ifconfig but it didn't work.
>> 
>> Thanks
>> russ
>Hello Russ
>
>If you have the kernel source code installed, edit serial.c to change
>the IRQ used for your serial port, and recompile the kernel.
>
>I not sure what Len was saying about INT 9 being paired with INT 2, and
>therefore it needs watching ???.
>Interrupts 8-15 are latched through the second of two interrupt
>controllers (0-7 are on the first one). The design of the original PC
>only had one interrupt controller and it would interrupt the CPU (808?)
>whenever any one of the 8 interrupts were triggered. With the advent of
>the second controller, it was decided to keep the original design, so
>now if interrupts 8-15 occur, they are latched by the second controller,
>and irq 2 is latched by the first controller, and then the CPU is
>interrupted. The interrupt service routine (ISR) knows all about this
>behaviour, and can deduce which IRQ (0-15) really is responsible for the
>interrupt.
>
>In short, IRQ 9 is fine.

Jon L. Miller, MCNE ASE
MMT Networks Pty Ltd
Ph:+61.8.9402.0639
Fx:+61.8.9402.2492
HP:http://www.wantree.com.au/~jlmiller
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