MSI MS-7641 Manuel D'instructions page 22

PCie Slot
the PCie slot supports the PCie interface expansion card.
PCi Slot
the PCi slot supports Lan card, SCSi card, uSB card, and other add-on cards
that comply with PCi specifications.
imPoRtant
When adding or removing expansion cards, make sure that you unplug the power
supply first. Read the documentation for the expansion card to configure any
necessary hardware or software settings for, such as jumpers, switches or BioS
configuration.
PCi interrupt Request Routing
the iRq, acronym of interrupt request line and pronounced i-R-q, are hardware
lines over which devices can send interrupt signals to the microprocessor. the PCi
iRq pins are typically connected to the PCi bus pins as follows:
order
Slot
PCi 
PCie x6 slot.
PCie x slot.
 2
int e# int F#
3 4
int G# int H#
MS-7641
2