Spurious IRQ7

[Grigori Khmyrov]

I have problem with extra interrupts at i686 industrial computer.
It never happened before with old VIA C3 400 MHz (100x4.0) board.
But I have an extra interrupts with new one VIA C3 667 MHz (133x5.0).
We have a hardware which produces signal every 5 ms. We use the signal 
as IRQ7.
Very rear I see an extra call of interrupt handler. Spurious IRQ7 
happens. I'm sure
that our hardware is not producing that signal. Is it any suggestion 
what can be
wrong. Can it be 8259A Interrupt Controller or RTEMS?
I'm using RTEMS 4.6.2 with i486 BSP.
Any suggestion how to fix or catch a problem appreciated.

Thank you,
Grigori