PCI-Express 1x Connector Pin Out

The PCI-Express bus supports 1x [2.5Gbps], 2x, 4x, 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs].
The PCI-Express [PCIe] 1x signal names and pinout are listed in the table below.
The 1x wide PCI Express bus is used as the replacement for the PCI expansion slot on PC motherboards, replacing the older and slower PCI slot.
Pinout tables for the other PCI Express widths are listed below the table.

PCI-Express 1x PinOut
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 RSVD Reserved +12v +12 volt power
4 GND Ground GND Ground
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
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 is the new serial bus addition to the PCI series of specifications. This 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 uses 8B/10B encoding [each 8 bit byte is translated into a 10 bit character in order to equalize the numbers of 1's and 0's sent, and the encoded signal contains an embedded clock]. PCI Express supports 1x [2.5Gbps], 2x, 4x, 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs]. The PCI-Express [PCIe] 1x signal names and pinout are listed above.

The differential pins [Lanes] listed in the pin out table above are LVDS [Low Voltage Differential Signaling]. The Electrical layer of LVDS listed above is described on the LVDS bus page.
The function of the JTAG pins are described on the JTAG bus page. The function of the SMbus pins listed above are described on the SMbus page.

PCIe Pinout Definitions:
PCI-Express 4x Connector Pinout and 4x signal names.
PCI-Express 8x Connector Pinout and 8x signal names.
PCI-Express 16x Connector Pinout and 16x signal names.
The main PCI-Express, PCIe bus page.

PC motherboard

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Modified 2/27/12
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