Popular connectors for computers

Pin out tables, some photos and parts of data come from Wikipedia.

Computers have various of connectors for their diverse use case. Overtime, old standard become obselete and new connector emerges. Some of them established their ground and dominates in their domains. It’s interesting to note their capability and how they got where they are. I am going to list some of them in this post and summarize key features. If you know a little bit about past standards, you might be amazed how technology eveolves step by step. Had if you know nothing about past standards, these connectors and standards would become old in the next decade or further in the future.


Starting from a golden standard of physical peripheral, this connector is Universal Serial Bus (USB). USB is everywhere. You can find them in laptops, cameras, drones, headsets, gaming consoles, and even industry machines. For example, latest Macbook Pro (2020) has 4 USB-C while their old predecessors have Thunderbolt connectors. Nowadays, most Android phones come with a USB-C connector.

USB has become complicated and confusing industry standard. The confusing part comes with multiple physical connector types and its different versions. Motherboards usually have different types of USB 3.x receptacles or jump wires. Despite its historical burden, the latest version, USB-C aims to move forward with all advantages and drawbacks from its past versions and receptacles. In the past, USB’s standard series are widely used. It has a larger connector than other series which is called Type-A. Type-A usually presents on a PC. Type-B has a more or less square shape. It is usually used in a display. Apart from those large receptacles, the mini series can be generally found in mobile phones. You can find a table on Wikipedia about different versions and receptacles. The interesting part of the chart is USB-C and USB4 as they are the only combination that are not deprecated after 2019.

USB offers comfort to users. Devices can be hot-plugged. Devices can configure themselves with operating systems and take power from USB cables. USB also provides great abstraction for manufacturers and developers. They can focus on device functions instead of physical connectors and protocol designs.

USB4 is the current standard which has only 1 receptacle (Type-C) with many technologies packed together. Considering USB 3.x series, USB 3.0, 3.1, 3.2 specification support a transfer mode of 5, 10, 20 Gbit/s. By the way, they were rebranded with a new set of confusing names, USB 3.2 Gen 1, USB 3.2 Gen 2, USB 3.2 Gen 2x2. Speaking of USB’s simplicity, the user shall be able to connect to a receptacle and expect a device to set up itself. You are not suppose to connect a cable to a USB recepatacle and wonder why things were wrong. With past standards, you wouldn’t be able to connect a cable that does not fit the receptacles. But their speed difference can be huge. For instance, USB disks can be extremly slow with USB 2 receptacle and USB 3 cable. That won’t be the problem for USB 4 (Type-C).

Type-C has 24 pins other than USB3’s 9 pins. Physically, USB Type-C receptacle looks smaller than its predecessor. It’s thin and packed.

Different Connectors

USB Type-C pinouts

USB-C receptacle A pin layout
Pin Name Description
A1 GND Ground return
A2 SSTXp1 SuperSpeed differential pair #1, TX, positive
A3 SSTXn1 SuperSpeed differential pair #1, TX, negative
A4 VBUS Bus power
A5 CC1 Configuration channel
A6 Dp1 USB 2.0 differential pair, position 1, positive
A7 Dn1 USB 2.0 differential pair, position 1, negative
A8 SBU1 Sideband use (SBU)
A9 VBUS Bus power
A10 SSRXn2 SuperSpeed differential pair #4, RX, negative
A11 SSRXp2 SuperSpeed differential pair #4, RX, positive
A12 GND Ground return
USB-C receptacle B pin layout
Pin Name Description
B12 GND Ground return
B11 SSRXp1 SuperSpeed differential pair #2, RX, positive
B10 SSRXn1 SuperSpeed differential pair #2, RX, negative
B9 VBUS Bus power
B8 SBU2 Sideband use (SBU)
B7 Dn2 USB 2.0 differential pair, position 2, negative</sup>
B6 Dp2 USB 2.0 differential pair, position 2, positive</sup>
B5 CC2 Configuration channel
B4 VBUS Bus power
B3 SSTXn2 SuperSpeed differential pair #3, TX, negative
B2 SSTXp2 SuperSpeed differential pair #3, TX, positive
B1 GND Ground return

Type-C has 4 power and 4 ground pins, 2 differential pairs for USB 2.0 data, 4 shielded differential pairs for USB 3.x data, and other pins. With USB Power Deliviery standard, a series of power profiles are supported. So a USB cable and power source can support 0.5W to 100W. Of course, it depends on the cable, host and devices for the power and data speed. USB 4 shall provide a maximum 40Gbit data link.

USB 4 introduces 5 alternate modes to support converters and other protocols. There are 3 types of USB Type-C cables. Firstly, full featured Type-C cable supports USB3.2 performance and other alternate connection such as DisplayPort, MHL, HDMI and Thunderbolt. Secondly, Thunderbolt 3 Type-C to Type-C (40Gbit/s) is another type of cable which can only be used as USB2 cable other than Thunderbolt 3. Lastly, adapter cables will be available. They will have their signs indicating their ability. The best option seems to be use full featured USB 4 Type-C cables and connectors. Otherwise, we have to respect what type of USB cables are. They might not work as expected even they look like the same.


Apple built Lightning connector and used it in every Apple mobile devices since 2012. It’s a great connector for its use. Lightning connector is not even replaced by USB-C while Macbook Pro strives to push forward the industry standard practice.

Lightning connector pin outs

Lightning Connector pin outs
Pin 1 GND Ground
Pin 2 L0p Lane 0 positive
Pin 3 L0n Lane 0 negative
Pin 4 ID0 Identification/control 0
Pin 5 PWR Power (charger or battery)
Pin 6 L1n Lane 1 negative
Pin 7 L1p Lane 1 positive
Pin 8 ID1 Identification/control 1
Lane 0 and 1 may swap in IC of device connector (lanes don't swap if the accessory identification chip is connected to the ID0 pin)

While the connector has certain layout, Lightning cables can be adapative because of Apple certified chip included in the cable. All pins seem to be able to switch between data and power. iPhone supports fast charging so the connector can support 18W charger at least. However, the speed is a secret. Sidecar feature which extends macOS screen to an iPad shows the eviendence of a fast transfering speed.


HDMI is usually used to connect a display device which is surprisingly popular. It’s not replaced by thunderbolt/USB4 yet, allegedly because of its price advantage. Being a audio/video transmission interface, HDMI has its roots with its predecessor DVI. Starting from HDMI 2.1, its encoding becomes similiar to USB3 and supports 48Gbit/s data transfering speed.

HDMI standard connector pinouts

HDMI (High-Definition Multimedia Interface) Type A Receptacle Pin out
Pin 1 TMDS Data2+
Pin 2 TMDS Data2 Shield
Pin 3 TMDS Data2−
Pin 4 TMDS Data1+
Pin 5 TMDS Data1 Shield
Pin 6 TMDS Data1−
Pin 7 TMDS Data0+
Pin 8 TMDS Data0 Shield
Pin 9 TMDS Data0−
Pin 10 TMDS Clock+
Pin 11 TMDS Clock Shield
Pin 12 TMDS Clock−
Pin 13 CEC
Pin 14
Pin 15 SCL (I²C serial clock for DDC)
Pin 16 SDA (I²C serial data for DDC)
Pin 17 Ground (for DDC, CEC, ARC, and HEC)
Pin 18 +5 V (min. 0.055 A)
Pin 19
  • Hot Plug Detect (all versions)
  • HEAC− (HDMI 1.4+, optional, HDMI Ethernet Channel and Audio Return Channel)


SATA (Serial AT Attachment) can be commonly found with storage devices. Various of hard drives and SSDs use SATA for power and data transfer. M.2 connector may also use SATA bus but those devices does not use SATA connectors.

SATA connectors

Its data connector has 7 pins and is much smaller than PATA connector.

SATA Standard connector, data segment
Pin # Mating Function
1 1st Ground
2 2nd A+ (transmit)
3 2nd A− (transmit)
4 1st Ground
5 2nd B− (receive)
6 2nd B+ (receive)
7 1st Ground
 — Coding notch

Its power connector has a 15 pin connector with various of voltages.

SATA Standard connector, power segment
Pin # Mating Function
 — Coding notch
1 3rd 3.3 V Power
2 3rd
3 2nd Enter/exit Power Disable (PWDIS) mode
(3.3 V Power, Pre-charge prior to SATA 3.3)
4 1st Ground
5 2nd
6 2nd
7 2nd 5 V Power, Pre-charge
8 3rd 5 V Power
9 3rd
10 2nd Ground
11 3rd Staggered spinup/activity
12 1st Ground
13 2nd 12 V Power, Pre-charge
14 3rd 12 V Power
15 3rd

The latest standard supports 6Gbit/s transfering speed.

PCI Express

PCI-E has been the primary choices for devices that are inter-connected on the motherboard. PCI-E device communicates point-to-point with each other and use packets. PCI-E link varies from one to 32 lanes. Devices can be plugged into another PCI-E sockets. Link speed is negotiated to the maximum possible speed.

PCI-E connector

PCI Express connector pinout (x1, x4, x8 and x16 variants)
Pin Side B Side A Description Pin Side B Side A Description
01 +12 V PRSNT1# Must connect to farthest PRSNT2# pin 50 HSOp(8) Reserved Lane 8 transmit data, + and −
02 +12 V +12 V Main power pins 51 HSOn(8) Ground
03 +12 V +12 V 52 Ground HSIp(8) Lane 8 receive data, + and −
04 Ground Ground 53 Ground HSIn(8)
05 SMCLK TCK SMBus and JTAG port pins 54 HSOp(9) Ground Lane 9 transmit data, + and −
06 SMDAT TDI 55 HSOn(9) Ground
07 Ground TDO 56 Ground HSIp(9) Lane 9 receive data, + and −
08 +3.3 V TMS 57 Ground HSIn(9)
09 TRST# +3.3 V 58 HSOp(10) Ground Lane 10 transmit data, + and −
10 +3.3 V aux +3.3 V Standby power 59 HSOn(10) Ground
11 WAKE# PERST# Link reactivation; fundamental reset 60 Ground HSIp(10) Lane 10 receive data, + and −
Key notch 61 Ground HSIn(10)
12 CLKREQ# Ground Clock Request Signal 62 HSOp(11) Ground Lane 11 transmit data, + and −
13 Ground REFCLK+ Reference clock differential pair 63 HSOn(11) Ground
14 HSOp(0) REFCLK− Lane 0 transmit data, + and − 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 PWRBRK# 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 pin Zero volt reference
45 HSOp(7) Ground Lane 7 transmit data, + and − Power pin Supplies power to the PCIe card
46 HSOn(7) Ground Card-to-host pin Signal from the card to the motherboard
47 Ground HSIp(7) Lane 7 receive data, + and − Host-to-card pin Signal from the motherboard to the card
48 PRSNT2# HSIn(7) Open drain May be pulled low or sensed by multiple cards
49 Ground Ground Sense pin Tied together on card
PCI Express x8 cards end at pin 49 Reserved Not presently used, do not connect


Connectors have different shapes optimized for different tasks. When devices or system evovles, connectors follows. A standard might try to extend its usage with designs but it does not fit every devices or future use cases. All these connectors provide essential functions such as power delivery, data transfering, some sorts of confugration pins. The way they were designed depends on its historical design and constraints.

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