MSI B75MA-E31 series User Manual page 22

pCie Slot
the pCis 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.
pCi interrupt request routing
irQ, or interrupt request lines, are hardware lines over which devices can send
interrupt requests to the processor. the pCi irQ pins are typically connected to
the pCi bus pins as followed:
order
Slot
pCi 
iMportANt
When adding or removing expansion cards, always turn off the power supply and
unplug the power supply power cable from the power outlet. read the expansion
card's documentation to check for any necessary additional hardware or software
changes.

 
iNt E# iNt F#
pCiE x6 slot.
pCiE x slot.
3-bit pCi Slot
3
iNt g# iNt h#
4