The PCI-Express bus supports 1x, 2x, 4x
[10Gbps], 8x, 12x, 16x, and 32x bus widths [transmit / receive pairs].
The PCI-Express [PCIe] 4x signal names and pinout are listed in the table
below.
The 4x wide PCI Express bus is not used on main-stream PC motherboards.
Links to additional PCI
Express pinout widths are listed after the table.
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 |
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 |
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(0) | 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 |
The PCI Express specification 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
which stands for: Low Voltage Differential Signaling. The Electrical
layer of LVDS is described on the LVDS bus
page.
The function of the JTAG pins listed
above 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 1x Connector Pinout and
1x 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.
---------------
Editor note; never connect to a signal any time you see a notation about a pin being unused, not used or reserved [RSVD]. The PCIe pin out table contains a number of lines that indicate reserved. Trying to send another ground line or some other signal into a pin not being used is just asking for trouble. Although rare, pins do change functionality in later versions of some standards. When the pin is currently unused, or not to be used, as in the case of a reserved pin may indicate a potential use in a later update.
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