Q: How's the IRQ sharing issue for BG7m motherboards?
A:

LAN and PCI-3 share an IRQ
AGP, PCI-1 and PCI-2 dividedly used an IRQ.

Manually assigning the IRQs is possible in BIOS "PnP/PCI configuration" submenu,
PIRQ_0 is for AGP
PIRQ_1 is for PCI-1
PIRQ_2 is for PCI-2
PIRQ_3 is for PCI-3 and LAN