PCI Express Bus Pinout

Sun, 15 May 2022 00:00:00 +0000

Slot Image

PCI Express, also known as PCI-E and officially abbreviated as PCIe, is an important computer bus standard. The slot is shown below:

Pinout

The table below lists the contacts on both sides of a PCI Express card edge connector. Side A is the solder side of the printed circuit board (PCB), and side B is the component side. The PRSNT1# and PRSNT2# pins are shorter than the other pins so the system can detect that a hot-plug card is fully inserted. WAKE# is used to wake the computer and must be pulled up from the auxiliary power rail to indicate that the card supports wake.

PCI Express connector pinout (x1, x4, x8, and x16 variants)
Pin	Side B	Side A	Description		Pin	Side B	Side A	Description
1	+12 V	PRSNT1#	Must connect to the farthest PRSNT2# pin	50	HSOp (8)	Reserved	Lane 8 transmit data, + and -
2	+12 V	+12 V		51	HSOn (8)	Ground
3	+12 V	+12 V	52	Ground	HSIp (8)	Lane 8 receive data, + and -
4	Ground	Ground	53	Ground	HSIn (8)
5	SMCLK	TCK	SMBus and JTAG port pins	54	HSOp (9)	Ground	Lane 9 transmit data, + and -
6	SMDAT	TDI	55	HSOn (9)	Ground
7	Ground	TDO	56	Ground	HSIp (9)	Lane 9 receive data, + and -
8	+3.3 V	TMS	57	Ground	HSIn (9)
9	TRST#	+3.3 V	58	HSOp (10)	Ground	Lane 10 transmit data, + and -
10	+3.3 V aux	+3.3 V	Auxiliary power	59	HSOn (10)	Ground
11	WAKE#	PERST#	Link activation; fundamental reset	60	Ground	HSIp (10)	Lane 10 receive data, + and -
Key notch	61	Ground	HSIn (10)
12	CLKREQ#	Ground	Clock request	62	HSOp (11)	Ground	Lane 11 transmit data, + and -
13	Ground	REFCLK+	Reference clock differential pair	63	HSOn (11)	Ground
14	HSOp (0)	REFCLK−	64	Ground	HSIp (11)	Lane 11 receive data, + and -
15	HSOn (0)	Ground		65	Ground	HSIn (11)
16	Ground	HSIp (0)	Lane 0 receive data, + and -	66	HSOp (12)	Ground	Lane 12 transmit data, + and -
17	PRSNT2#	HSIn (0)	67	HSOn (12)	Ground
18	Ground	Ground		68	Ground	HSIp (12)	Lane 12 receive data, + and -
PCI Express x1 cards end at pin 18	69	Ground	HSIn (12)
19	HSOp (1)	Reserved	Lane 1 transmit data, + and -	70	HSOp (13)	Ground	Lane 13 transmit data, + and -
20	HSOn (1)	Ground	71	HSOn (13)	Ground
21	Ground	HSIp (1)	Lane 1 receive data, + and -	72	Ground	HSIp (13)	Lane 13 receive data, + and -
22	Ground	HSIn (1)	73	Ground	HSIn (13)
23	HSOp (2)	Ground	Lane 2 transmit data, + and -	74	HSOp (14)	Ground	Lane 14 transmit data, + and -
24	HSOn (2)	Ground	75	HSOn (14)	Ground
25	Ground	HSIp (2)	Lane 2 receive data, + and -	76	Ground	HSIp (14)	Lane 14 receive data, + and -
26	Ground	HSIn (2)	77	Ground	HSIn (14)
27	HSOp (3)	Ground	Lane 3 transmit data, + and -	78	HSOp (15)	Ground	Lane 15 transmit data, + and -
28	HSOn (3)	Ground	79	HSOn (15)	Ground
29	Ground	HSIp (3)	Lane 3 receive data, + and -	80	Ground	HSIp (15)	Lane 15 receive data, + and -
30	Reserved	HSIn (3)	81	PRSNT2#	HSIn (15)
31	PRSNT2#	Ground		82	Reserved	Ground
32	Ground	Reserved
PCI Express x4 cards end at pin 32
33	HSOp (4)	Reserved	Lane 4 transmit data, + and -
34	HSOn (4)	Ground
35	Ground	HSIp (4)	Lane 4 receive data, + and -
36	Ground	HSIn (4)
37	HSOp (5)	Ground	Lane 5 transmit data, + and -
38	HSOn (5)	Ground
39	Ground	HSIp (5)	Lane 5 receive data, + and -
40	Ground	HSIn (5)
41	HSOp (6)	Ground	Lane 6 transmit data, + and -
42	HSOn (6)	Ground
43	Ground	HSIp (6)	Lane 6 receive data, + and -	Legend
44	Ground	HSIn (6)	Ground pins	Zero-voltage reference
45	HSOp (7)	Ground	Lane 7 transmit data, + and -	Power pins	Power supplied to the PCIe card
46	HSOn (7)	Ground	Output pins	Signals from the PCIe card to the motherboard
47	Ground	HSIp (7)	Lane 7 receive data, + and -	Input pins	Signals from the motherboard to the PCIe card
48	PRSNT2#	HSIn (7)	Open drain	Can be pulled low or used to detect multiple cards
49	Ground	Ground		Presence-detect pins	Card presence connection
PCI Express x8 cards end at pin 49	Reserved	Currently unused; do not connect

PCI Express on KnightLi Blog

PCI Express Bus Pinout

Slot Image

Pinout