The next problem is that in spite of this, the ethernet chip doesn't generate interrupts anymore.
Is there any additional configuration /setup that I need to do?
I had the exact problem with the 440BX.
Is the IRQ actually routed correctly?
On many bridges Linux expects the BIOS to have properly set up the IRQ routing from the PIRQ to the IRQ. Just having the table correct may not be enough. On the 440BX I had to do it manually. Boot COTS and compare the lspci -xxx of your northbridge with that of linuxBIOS and then go look for differences in the PIRQ to IRQ n routes.
-- Richard A. Smith