[plug] eth0 and ppp

[Len Bird]

"Jon L. Miller" wrote:

> 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
> EM:mailto:jlmiller at wantree.com.au

Yes that is what I meant, simply put you need to make your Modem Connection
IRQ3 and then find out which IRQs are available for the Ethernet Card.
Usually you can get up to IRQs 10-11 or 15 which the Ethernet Cards should
support. Alternatively however, IF you have a relatively new Main Board with
USB support, the Mouse input is no longer on COM-1 and IRQ-4 which means that
you have this as an alternative for your Modem Connection. I know from
experience that if both Ethernet and Serial Ports use the same IRQ neither
will function at all. DOS does support shared Interrupts provided that the
resources are not called together, OS/2 will not accept shared IRQs at all, I
do not know the situation with Linux, perhaps John Summerfield can answer
that,

Cheers ,

Len Bird