A connecting apparatus comprises a riser card (10) and a slot (20). The riser card comprises a PCI-X slot (13), a PCI-E slot (11), a first connector (15), a second connector (17) and a third connector (19). The first connector set a serial of PCI-X signal pads (151) on one side thereof. The second connector is adapted to provide power and ground signals. The third connector set a serial of PCI-E signal pads (191) on the same side thereof as the first connector. The slot is defined on a circuit board for the riser card inserted therein. The slot comprises a first portion (21) and a second portion (23) coupling to the second connector. The first portion comprises a first side with a series of PCI-X signal pins (211) coupling to the serial of PCI-X signal pads of the first connector, when the riser card is inserted into the slot in a first direction with the first connector inserted into the first portion. The first portion comprises a second side with a series of PCI-E signal pins (191) coupling to the serial of PCI-E signal pads of the third connector, when the riser card is inserted into the slot in a second direction which is reverse to the first direction with the third connector inserted into the second portion.