Computer buses and slots connectors pinouts
PCI Express (PCIe, PCI-e) is a high-speed serial computer expansion bus standard.

PCI Express as a high-bandwidth, low pin count, serial, interconnect technology. It was designed to replace the older PCI and AGPbus standards. PCIe has numerous improvements over the older standards, including higher maximum system bus throughput, lower I/O pin count and smaller physical footprint, better performance scaling for bus devices, a more detailed error detection and reporting mechanism (Advanced Error Reporting, AER), and native hot-swap functionality. PCI Express architecture provides a high performance I/O infrastructure for Desktop Platforms with transfer rates starting at 2.5 Giga transfers per second over a x1 PCI Express lane for Gigabit Ethernet, TV Tuners, Firewire 1394a/b controllers, and general purpose I/O. PCI Express architecture provides a high performance graphics infrastructure for Desktop Platforms doubling the capability of existing AGP8x designs with transfer rates of 4.0 Gigabytes per second over a x16 PCI Express lane for graphics controllers. A lane is composed of two differential signaling pairs, with one pair for receiving data and the other for transmitting.

ExpressCard utilizing PCI Express interface, developed by the PCMCIA group for mobile computers. PCI Express Advanced Power Management features help to extend platform battery life and to enable users to work anywhere, without an AC power source. The PCI Express electrical interface is also used in some computer storage interfaces SATA Express and M.2.

The broad adoption of PCI Express in the mobile, enterprise and communication segments enables convergence through the re-use of a common interconnect technology.

PCI-E is a serial bus which uses two low-voltage differential LVDS pairs, at 2.5Gb/s in each direction [one transmit, and one receive pair]. PCI Express supports 1x [2.5Gbps], 2x, 4x, 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs].

The differential pins [Lanes] listed in the pin out table above are LVDS which stands for: Low Voltage Differential Signaling.

PCI-Express 1x Connector Pin-Out

Pin

Side B Connector

Side A Connector

# Name Description Name Description
1 +12v +12 volt power PRSNT#1 Hot plug presence detect
2 +12v +12 volt power +12v +12 volt power
3 +12v +12 volt power +12v +12 volt power
4 GND Ground GND Ground
5 SMCLK SMBus clock JTAG2 TCK
6 SMDAT SMBus data JTAG3 TDI
7 GND Ground JTAG4 TDO
8 +3.3v +3.3 volt power JTAG5 TMS
9 JTAG1 +TRST# +3.3v +3.3 volt power
10 3.3Vaux 3.3v volt power +3.3v +3.3 volt power
11 WAKE# Link Reactivation PWRGD Power Good

Mechanical Key

12 RSVD Reserved GND Ground
13 GND Ground REFCLK+ Reference Clock
Differential pair
14 HSOp(0) Transmitter Lane 0,
Differential pair
REFCLK-
15 HSOn(0) GND Ground
16 GND Ground HSIp(0) Receiver Lane 0,
Differential pair
17 PRSNT#2 Hotplug detect HSIn(0)
18 GND Ground GND Ground

PCI-Express 4x Connector Pin-Out

Pin

Side B Connector

Side A Connector

# Name Description Name Description
1 +12v +12 volt power PRSNT#1 Hot plug presence detect
2 +12v +12 volt power +12v +12 volt power
3 +12v +12 volt power +12v +12 volt power
4 GND Ground GND Ground
5 SMCLK SMBus clock JTAG2 TCK
6 SMDAT SMBus data JTAG3 TDI
7 GND Ground JTAG4 TDO
8 +3.3v +3.3 volt power JTAG5 TMS
9 JTAG1 +TRST# +3.3v +3.3 volt power
10 3.3Vaux 3.3v volt power +3.3v +3.3 volt power
11 WAKE# Link Reactivation PWRGD Power Good

Mechanical Key

12 RSVD Reserved GND Ground
13 GND Ground REFCLK+ Reference Clock
Differential pair
14 HSOp(0) Transmitter Lane 0,
Differential pair
REFCLK-
15 HSOn(0) GND Ground
16 GND Ground HSIp(0) Receiver Lane 0,
Differential pair
17 PRSNT#2 Hotplug detect HSIn(0)
18 GND Ground GND Ground
19 HSOp(1) Transmitter Lane 1,
Differential pair
RSVD Reserved
20 HSOn(1) GND Ground
21 GND Ground HSIp(1) Receiver Lane 1,
Differential pair
22 GND Ground HSIn(1)
23 HSOp(2) Transmitter Lane 2,
Differential pair
GND Ground
24 HSOn(2) GND Ground
25 GND Ground HSIp(2) Receiver Lane 2,
Differential pair
26 GND Ground HSIn(2)
27 HSOp(3) Transmitter Lane 3,
Differential pair
GND Ground
28 HSOn(3) GND Ground
29 GND Ground HSIp(3) Receiver Lane 3,
Differential pair
30 RSVD Reserved HSIn(3)
31 PRSNT#2 Hot plug detect GND Ground
32 GND Ground RSVD Reserved

PCI-Express 8x Connector Pin-Out

Pin

Side B Connector

Side A Connector

# Name Description Name Description
1 +12v +12 volt power PRSNT#1 Hot plug presence detect
2 +12v +12 volt power +12v +12 volt power
3 +12v +12 volt power +12v +12 volt power
4 GND Ground GND Ground
5 SMCLK SMBus clock JTAG2 TCK
6 SMDAT SMBus data JTAG3 TDI
7 GND Ground JTAG4 TDO
8 +3.3v +3.3 volt power JTAG5 TMS
9 JTAG1 +TRST# +3.3v +3.3 volt power
10 3.3Vaux 3.3v volt power +3.3v +3.3 volt power
11 WAKE# Link Reactivation PWRGD Power Good

Mechanical Keycard

12 RSVD Reserved GND Ground
13 GND Ground REFCLK+ Reference Clock
Differential pair
14 HSOp(0) Transmitter Lane 0,
Differential pair
REFCLK-
15 HSOn(0) GND Ground
16 GND Ground HSIp(0) Receiver Lane 0,
Differential pair
17 PRSNT#2 Hotplug detect HSIn(0)
18 GND Ground GND Ground
19 HSOp(1) Transmitter Lane 1,
Differential pair
RSVD Reserved
20 HSOn(1) GND Ground
21 GND Ground HSIp(1) Receiver Lane 1,
Differential pair
22 GND Ground HSIn(1)
23 HSOp(2) Transmitter Lane 2,
Differential pair
GND Ground
24 HSOn(2) GND Ground
25 GND Ground HSIp(2) Receiver Lane 2,
Differential pair
26 GND Ground HSIn(2)
27 HSOp(3) Transmitter Lane 3,
Differential pair
GND Ground
28 HSOn(3) GND Ground
29 GND Ground HSIp(3) Receiver Lane 3,
Differential pair
30 RSVD Reserved HSIn(3)
31 PRSNT#2 Hot plug detect GND Ground
32 GND Ground RSVD Reserved
33 HSOp(4) Transmitter Lane 4,
Differential pair
RSVD Reserved
34 HSOn(4) GND Ground
35 GND Ground HSIp(4) Receiver Lane 4,
Differential pair
36 GND Ground HSIn(4)
37 HSOp(5) Transmitter Lane 5,
Differential pair
GND Ground
38 HSOn(5) GND Ground
39 GND Ground HSIp(5) Receiver Lane 5,
Differential pair
40 GND Ground HSIn(5)
41 HSOp(6) Transmitter Lane 6,
Differential pair
GND Ground
42 HSOn(6) GND Ground
43 GND Ground HSIp(6) Receiver Lane 6,
Differential pair
44 GND Ground HSIn(6)
45 HSOp(7) Transmitter Lane 7,
Differential pair
GND Ground
46 HSOn(7) GND Ground
47 GND Ground HSIp(7) Receiver Lane 7,
Differential pair
48 PRSNT#2 Hot plug detect HSIn(7)
49 GND Ground GND Ground

PCI-Express 16x Connector Pin-Out

Pin

Side B Connector

Side A Connector

# Name Description Name Description
1 +12v +12 volt power PRSNT#1 Hot plug presence detect
2 +12v +12 volt power +12v +12 volt power
3 +12v +12 volt power +12v +12 volt power
4 GND Ground GND Ground
5 SMCLK SMBus clock JTAG2 TCK
6 SMDAT SMBus data JTAG3 TDI
7 GND Ground JTAG4 TDO
8 +3.3v +3.3 volt power JTAG5 TMS
9 JTAG1 +TRST# +3.3v +3.3 volt power
10 3.3Vaux 3.3v volt power +3.3v +3.3 volt power
11 WAKE# Link Reactivation PWRGD Power Good

Mechanical Key

12 RSVD Reserved GND Ground
13 GND Ground REFCLK+ Reference Clock
Differential pair
14 HSOp(0) Transmitter Lane 0,
Differential pair
REFCLK-
15 HSOn(0) GND Ground
16 GND Ground HSIp(0) Receiver Lane 0,
Differential pair
17 PRSNT#2 Hotplug detect HSIn(0)
18 GND Ground GND Ground
19 HSOp(1) Transmitter Lane 1,
Differential pair
RSVD Reserved
20 HSOn(1) GND Ground
21 GND Ground HSIp(1) Receiver Lane 1,
Differential pair
22 GND Ground HSIn(1)
23 HSOp(2) Transmitter Lane 2,
Differential pair
GND Ground
24 HSOn(2) GND Ground
25 GND Ground HSIp(2) Receiver Lane 2,
Differential pair
26 GND Ground HSIn(2)
27 HSOp(3) Transmitter Lane 3,
Differential pair
GND Ground
28 HSOn(3) GND Ground
29 GND Ground HSIp(3) Receiver Lane 3,
Differential pair
30 RSVD Reserved HSIn(3)
31 PRSNT#2 Hot plug detect GND Ground
32 GND Ground RSVD Reserved
33 HSOp(4) Transmitter Lane 4,
Differential pair
RSVD Reserved
34 HSOn(4) GND Ground
35 GND Ground HSIp(4) Receiver Lane 4,
Differential pair
36 GND Ground HSIn(4)
37 HSOp(5) Transmitter Lane 5,
Differential pair
GND Ground
38 HSOn(5) GND Ground
39 GND Ground HSIp(5) Receiver Lane 5,
Differential pair
40 GND Ground HSIn(5)
41 HSOp(6) Transmitter Lane 6,
Differential pair
GND Ground
42 HSOn(6) GND Ground
43 GND Ground HSIp(6) Receiver Lane 6,
Differential pair
44 GND Ground HSIn(6)
45 HSOp(7) Transmitter Lane 7,
Differential pair
GND Ground
46 HSOn(7) GND Ground
47 GND Ground HSIp(7) Receiver Lane 7,
Differential pair
48 PRSNT#2 Hot plug detect HSIn(7)
49 GND Ground GND Ground
50 HSOp(8) Transmitter Lane 8,
Differential pair
RSVD Reserved
51 HSOn(8) GND Ground
52 GND Ground HSIp(8) Receiver Lane 8,
Differential pair
53 GND Ground HSIn(8)
54 HSOp(9) Transmitter Lane 9,
Differential pair
GND Ground
55 HSOn(9) GND Ground
56 GND Ground HSIp(9) Receiver Lane 9,
Differential pair
57 GND Ground HSIn(9)
58 HSOp(10) Transmitter Lane 10,
Differential pair
GND Ground
59 HSOn(10) GND Ground
60 GND Ground HSIp(10) Receiver Lane 10,
Differential pair
61 GND Ground HSIn(10)
62 HSOp(11) Transmitter Lane 11,
Differential pair
GND Ground
63 HSOn(11) GND Ground
64 GND Ground HSIp(11) Receiver Lane 11,
Differential pair
65 GND Ground HSIn(11)
66 HSOp(12) Transmitter Lane 12,
Differential pair
GND Ground
67 HSOn(12) GND Ground
68 GND Ground HSIp(12) Receiver Lane 12,
Differential pair
69 GND Ground HSIn(12)
70 HSOp(13) Transmitter Lane 13,
Differential pair
GND Ground
71 HSOn(13) GND Ground
72 GND Ground HSIp(13) Receiver Lane 13,
Differential pair
73 GND Ground HSIn(13)
74 HSOp(14) Transmitter Lane 14,
Differential pair
GND Ground
75 HSOn(14) GND Ground
76 GND Ground HSIp(14) Receiver Lane 14,
Differential pair
77 GND Ground HSIn(14)
78 HSOp(15) Transmitter Lane 15,
Differential pair
GND Ground
79 HSOn(15) GND Ground
80 GND Ground HSIp(15) Receiver Lane 15,
Differential pair
81 PRSNT#2 Hot plug present detect HSIn(15)
82 RSVD#2 Hot Plug Detect GND Ground

 

PRSNT#1 is connected to GND on motherboard.
Add on card needs to have PRSNT#1 connected to one of PRSNT#2 depending what type of connector is in use.
 

PCI-express standards

PCI Express 1.0a

In 2003, PCI-SIG introduced PCIe 1.0a, with a per-lane data rate of 250 MB/s and a transfer rate of 2.5 gigatransfers per second (GT/s). Transfer rate is expressed in transfers per second instead of bits per second because the number of transfers includes the overhead bits, which do not provide additional throughput; PCIe 1.x uses an 8b/10b encoding scheme, resulting in a 20% (= 2/10) overhead on the raw channel bandwidth.

PCI Express 2.0

PCI-SIG announced the availability of the PCI Express Base 2.0 specification on 15 January 2007. The PCIe 2.0 standard doubles the transfer rate compared with PCIe 1.0 to 5 GT/s and the per-lane throughput rises from 250 MB/s to 500 MB/s. Consequently, a 32-lane PCIe connector (×32) can support an aggregate throughput of up to 16 GB/s. PCIe 2.0 motherboard slots are fully backward compatible with PCIe v1.x cards. PCIe 2.0 cards are also generally backward compatible with PCIe 1.x motherboards, using the available bandwidth of PCI Express 1.1. Overall, graphic cards or motherboards designed for v2.0 will work with the other being v1.1 or v1.0a.  Like 1.x, PCIe 2.0 uses an 8b/10b encoding scheme, therefore delivering, per-lane, an effective 4 Gbit/s max transfer rate from its 5 GT/s raw data rate.

PCI Express 2.1

PCI Express 2.1 (dated March 4, 2009) supports a large proportion of the management, support, and troubleshooting systems planned for full implementation in PCI Express 3.0. However, the speed is the same as PCI Express 2.0. The increase in power from the slot breaks backward compatibility between PCI Express 2.1 cards and some older motherboards with 1.0/1.0a, but most motherboards with PCI Express 1.1 connectors are provided with a BIOS update by their manufacturers through utilities to support backward compatibility of cards with PCIe 2.1.

PCI Express 3.0

PCI Express 3.0 specification was made available in November 2010. New features for the PCI Express 3.0 specification include a number of optimizations for enhanced signaling and data integrity, including transmitter and receiver equalization, PLL improvements, clock data recovery, and channel enhancements for currently supported topologies. PCI Express 3.0 upgrades the encoding scheme to 128b/130b from the previous 8b/10b encoding, reducing the bandwidth overhead from 20% of PCI Express 2.0 to approximately 1.54% (= 2/130). This is achieved by XORing a known binary polynomial as a scrambler to the data stream in a feedback topology. PCI Express 3.0's 8 GT/s bit rate effectively delivers 985 MB/s per lane, nearly doubling the lane bandwidth relative to PCI Express 2.0.

PCI Express 4.0

PCI Express 4.0 was officially announced on 2017, providing a 16 GT/s bit rate that doubles the bandwidth provided by PCI Express 3.0, while maintaining backward and forward compatibility in both software support and used mechanical interface. PCI Express 4.0 specs will also bring OCuLink-2, an alternative to Thunderbolt connector. OCuLink version 2 will have up to 16 GT/s (8 GB/s total for ×4 lanes), while the maximum bandwidth of a Thunderbolt 3 connector is 5 GB/s. Additionally, active and idle power optimizations are to be investigated.

36 pin PCI-Express x1 connector layout
36 pin PCI-Express x1 connector
164 pin PCI-Express 16x connector layout
164 pin PCI-Express 16x connector
According to 16 reports in our database (14 positive and 1 negative) this pinout should be correct.

Is this pinout
PCI Express 1x, 4x, 8x, 16x bus visual pinout:
PCI Express 1x, 4x, 8x, 16x bus diagram
click to enlarge
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