This is part of The Pile, a partial archive of some open source mailing lists and newsgroups.
Date: Sun, 17 Dec 2000 12:23:17 -0800
To: SVLUG <svlug@svlug.org>
Subject: Re: [svlug] IRQ: how to find out which is to be used?
From: Rick Moen <rick@linuxmafia.com>
begin Erik Steffl quotation:
> In my case both irq 9 and irq 11 are free (not used) but only
> setserial /dev/ttyS2 irq 9 works. how do I find that out? (without
> using win or trying all unused IRQs)
My preferred solution is the one nobody wants to use: know your machine.
http://linuxmafia.com/pub/hardware/chart.txt
--
Cheers, "Reality is not optional."
Rick Moen -- Thomas Sowell
rick@linuxmafia.com
===
Date: Sun, 17 Dec 2000 12:36:26 -0800
To: SVLUG <svlug@svlug.org>
Subject: Re: [svlug] IRQ: how to find out which is to be used?
From: Rick Moen <rick@linuxmafia.com>
begin Erik Steffl quotation:
> I have also a strange related story to contribute: I have this [ISA
> PnP] modem along with other cards (ISA: sb awe 64, PCI: voodoo 3,
> network card lne100tx) and it has been using IRQ 11 for ages. Since
> the network card does not work properly, I taken all the cards out
> (except of video&network) and tested the network card (just to see if
> there are any strange confilcts, becuase previously I noticed that
> network card conflicted with soundcard when inserted in particular PCI
> slot (even though soundcard is ISA card)). No config files were
> changed, AFAIK.
>
> Later on I put all the cards back into computer (exactly the same
> slots) and suddenly I noticed that modem works incredibly slow, it
> couldn't connect (timeouts). I suspected IRQ so I rebooted win95 and
> sure enough, IRQ for the modem was now 9 (it was 11 before). I
> rebooted back to linux, changed IRQ to 9 and now the modem works.
>
> neither 9 nor 11 is used by anything else. however, network card used
> to be 9 and now is 10.
ISA PnP devices get assigned their hardware resources (including IRQs)
dynamically at Power-On Self Test time by the ISA PnP controller chip.
PCI devices get the same treatment from the PCI controller chip. Both
chips have at their disposal hardware resources allowed to their "pools"
of same in your BIOS Setup -- which you'll want to review. Other
hardware resources may be reserved (in BIOS Setup) for non-PnP ISA
devices.
Personally, I try to ensure that as many ISA PnP devices as possible get
jumpered for non-PnP operation: It's bloody irritating to see the
machine decide to rearrange my IRQ assignments at a whim. That's why,
if you insist on internal ISA modems, it's a good idea to at least
choose ones that can be jumpered for non-PnP (such as, typically, U.S.
Robotics). Then, I configure the motherboard BIOS to tell the ISA PnP
and PCI controller chips "hands off" that IRQ, and others likewise
assigned to non-PnP ISA.
Some truly good motherboard BIOSes will actually allow you to assign
IRQs by expansion slot. (Fortunately, I've not had to buy motherboards
lately; the schlockmeisters may have taken over completely.) And, of
course, this IRQ-sharing stuff is Right Out.
--
Cheers, "Reality is not optional."
Rick Moen -- Thomas Sowell
rick@linuxmafia.com
===
Date: Sun, 17 Dec 2000 16:44:22 -0500
From: Brian Coyle <brianc@magicnet.net>
To: SVLUG <svlug@svlug.org>
Subject: Re: [svlug] IRQ: how to find out which is to be used?
Erik Steffl wrote:
>
> Brian Coyle wrote:
> >
> > Erik Steffl wrote:
> > >
> > > It is ISA PnP card, can use different IRQs.
> > >
> > > My main question is: how do I find out which IRQ it uses
> > > using linux tools?
> >
> > $ man 8 pnpdump
> > $ man 5 isapnp.conf
> > $ man 8 isapnp
>
> pnpdump gives the possible configurations, not the one to use.
>
> it has the -c switch that attempts to find safe config but it uses
> info about what is already used (/etc/interrupts and /etc/isapnp.gone),
> which is not what I am asking about. In my case both irq 9 and irq 11
> are free (not used) but only setserial /dev/ttyS2 irq 9 works. how do I
> find that out? (without using win or trying all unused IRQs)
>
HMMM... how 'bout-
$ dmesg | grep -i irq
one of my systems shows this:
$ dmesg | grep -i irq
Serial driver version 4.27 with MANY_PORTS MULTIPORT SHARE_IRQ enabled
ttyS00 at 0x03f8 (irq = 4) is a 16550A
ttyS01 at 0x02f8 (irq = 3) is a 16550A
SIS5513: not 100% native mode: will probe irqs later
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
enable_irq() unbalanced from c481c55a
eth0: Digital DS21140 Tulip at 0xf080, 00 c0 6d 15 00 1f, IRQ 7.
Even though
$ cat /proc/interrupts
CPU0
0: 1965084 XT-PIC timer
1: 7788 XT-PIC keyboard
2: 0 XT-PIC cascade
7: 297539 XT-PIC eth0
8: 1 XT-PIC rtc
10: 22600 XT-PIC aic7xxx
11: 1229723 XT-PIC MSS audio codec
12: 337548 XT-PIC PS/2 Mouse
13: 0 XT-PIC fpu
14: 16 XT-PIC ide0
shows the serial irq's unused...
HTH!
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