Re: 2.6.8-12-amd64-k8 raid1 freezes with spurious interrupts

[A J Stiles <deb64@earthshod.co.uk>]

On Tuesday 08 August 2006 12:04, Harm Behrens wrote:
> Hello,
>
> I have a problem with an Asus A8N-SLI motherboard, kernel 2.6.8-12-amd64-k8
> and raid1 on two 300 GB Samsung harddrives
>
> Regulary while the raid syncs I get "spurious interrupts 8859 IRQ7 etc."
> and the system freezes!

I've seen "spurious interrupt IRQ7" errors on boards with an unused Centronics 
printer port.  Does your mobo have such a port?  If so, do you still get 
these errors with a printer plugged in?

If the error does not manifest with a printer on the port then it is caused by 
the pull-up resistance on pin 10 of the port  {which creates an interrupt 
when it goes to 0V}  being too high.  In fact, the resistor might be absent 
altogether and the board will still apparently pass testing.  But the pin 
will pick up noise, and eventually cause a false interrupt signal.

You could try artificially tying pin 10 to +5V via a resistor of 4k7 or 
thereabouts.  Pin 14  {which tells the printer whether to do a line feed 
whenever it gets a CR, or only when it receives an explicit LF}  is normally 
held high, so this might well do:  just connect a 4.7kohm resistor  (yellow, 
violet, red)  from pin 14 to pin 10  {If you measure with an AVO you should 
see +5V between pin 14 and the PC chassis}.

More comprehensive circuit, which will get +5V from anywhere it can find it:  
this can be built within a 25-pin DIN plug.  Use any old diodes you can find.  
1N4148s are as good as anything.  Join all the cathodes together and connect 
via a 4k7 resistor to pin 10.  Connect the anodes to pins 1, 2, 3, 4, 5, 6, 
7, 8, 9, 14, 16 and 17.

1  ---|>|---*---[4k7]--- 10
            |
2  ---|>|---*
            |
3  ---|>|---*
            |
4  ---|>|---*
            |
5  ---|>|---*
            |
6  ---|>|---*
            |
7  ---|>|---*
            |
8  ---|>|---*
            |
9  ---|>|---*
            |
14 ---|>|---*
            |
16 ---|>|---*
            |
17 ---|>|---'


Alternatively, if you can find a +5V supply somewhere inside the PC, you could 
solder a resistor between there and the motherboard connector itself.  
This -should- not stop a printer working; but if the cable is very long, the 
printer may have trouble pulling its zeros low enough and so skip characters.  
In this case, just increase the resistance till it does work.

If plugging in a printer doesn't cure the problem, or if there is no 
Centronics port, then this is not the answer.  What is using IRQ7 in your 
setup?

-- 
AJS
delta echo bravo six four at earthshod dot co dot uk