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Re: /proc/interrupts - conflicts?



Brian Mays wrote:
> 
> mark@ist.flinders.edu.au (Mark Phillips) writes:
> 
> > Can you tell, just by looking at /proc/interrupts, whether there is an
> > interrupt conflict?
> >
> > In particular, how does it work for pcmcia cards for a laptop?
> 
> Well, let's take a look.  Here's what my /proc/interrupts says:
> 
>  0:    3736694   timer
>  1:      60282   keyboard
>  2:          0   cascade
>  3:      22149 + serial
>  5:          1   sound blaster
>  9:     182163   3c589_cs
> 11:          8   i82365
> 13:          1   math error
> 14:     351147 + ide0
> 
> Here's what this means:
> 
> Interrupt  0: the timer
> Interrupt  1: the keyboard
> Interrupt  2: same as 9
> Interrupt  3: my serial mouse
> Interrupt  5: my sound card
> Interrupt  9: my PCMCIA network card
> Interrupt 11: the PCMCIA controller
> Interrupt 14: my hard drive
> 
> You can search for conflicts caused by the PCMCIA utilities by listing
> the contents of /proc/interrupts with the PCMCIA card manager disabled
> (execute as root `/etc/init.d/pcmcia stop') and observing at what
> interrupts are being used.  On my system, the sound card likes to use
> irq 5.  Therefore, I exclude this interrupt from being used by a PCMCIA
> card by placing the following line in /etc/pcmcia/config.opts:
> 
> exclude irq 5
> 
> Without this line, my sound card does not work sometimes because the
> PCMCIA system seizes irq 5.  This is evident in /proc/interrupts as a
> line such as
> 
>  5:       2149   3c589_cs
> 
> This shows that irq 5 has been assigned to my PCMCIA network card and
> hence is not available for use by the sound card.
> 
> When worrying about interrupt conflicts, keep in mind that use irq 4
> is often used for the first and third serial ports and irq 3 is often
> used for the second and fourth serial ports.  The parallel port likes
> to use irq 7, so you might want to exclude it in config.opts if you
> are hooked up to a printer or are using plip to connect to another
> computer.  If, however, you never use your parallel port and your
> PCMCIA cards at the same time, then you probably don't need to worry
> about it.
> 
> Brian
> 
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Also I have found that not all of the irq's are listed in
/proc/interrupts.

I had a problem some time ago and I found buried in /proc/pci is a
further
listing of devices used on the system:  Here is what mine looks like:

PCI devices found:
  Bus  0, device  10, function  0:
    Ethernet controller: Realtek 8029 (rev 0).
      Medium devsel.  IRQ 5.  
      I/O at 0xfce0.
  Bus  0, device   8, function  0:
    VGA compatible controller: Cirrus Logic GD 5430 (rev 72).
      Fast devsel.  IRQ 11.  
      Prefetchable 32 bit memory at 0xfd000000.
  Bus  0, device   1, function  0:
    ISA bridge: VLSI 82C593-FC1 (rev 1).
      Medium devsel.  Fast back-to-back capable.  Master Capable.  No
bursts.  
  Bus  0, device   0, function  0:
    Host bridge: VLSI 82C592-FC1 (rev 1).
      Medium devsel.  Fast back-to-back capable.  Master Capable. 
Latency=16.  

and here is what /proc/interrupts shows:

 0:    1519215   timer
 1:       1367   keyboard
 2:          0   cascade
 3:     871156 + serial
 5:          0   NE2000
 8:          1 + rtc
 9:      29117 + aha152x
10:          2   sound blaster
12:     601902   PS/2 Mouse
13:          1   math error
14:      26586 + ide0

notice that irq 11 is not listed in /proc/interrupts.  This little
problem created 
some serious problems with my sound card, and scsi controller when I
added the scsi
to my system.  I hope that this helps.
-- 
          0 0
           "       http://www.netaxs.com/~ldc/
_______ooO ~ Ooo_______________________________________________

LeRoy D. Cressy     	 /\_/\		ldc@netaxs.com
Computer Consulting 	( o.o )		(215) 389-5870
		 	 > ^ <


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