Hardware · Topic 2 of 13
Video and Peripheral Cables
Identify HDMI, DisplayPort, DVI, VGA, USB, Thunderbolt, SATA, serial and Lightning cables and connectors, and know what each one carries and uses.
- 4 min
- VGA is analog and carries video only; HDMI and DisplayPort carry digital video and audio.
- DVI-D is digital only, DVI-A analog only and DVI-I both.
- USB 2.0 is 480 Mbps, USB 3.0 is 5 Gbps and USB 3.1 Gen 2 is 10 Gbps.
What it is
Computers connect to displays, drives and accessories through many cable types. Each type has a connector shape, a signal type and a use.
You need to recognise a connector by sight and know what it carries. Network cables are covered on the next page.
How it works
Video connectors
| Connector | Signal | Carries audio | Notes |
|---|---|---|---|
| Video Graphics Array (VGA) | Analog | No | 15 pin blue D shaped connector, held by thumbscrews; oldest of the group |
| Digital Visual Interface (DVI) | Digital, analog or both | No | DVI-D is digital only, DVI-A analog only, DVI-I carries both |
| High Definition Multimedia Interface (HDMI) | Digital | Yes | Common on TVs, monitors and laptops; also has smaller mini and micro versions |
| DisplayPort | Digital | Yes | Common on monitors and graphics cards; can drive several screens in a chain |
| USB-C | Digital | Yes, in alternate mode | One reversible port for data, power and video on many laptops |
VGA is analog, so it can show interference and is weaker than digital at high resolution. A DVI-D connector has no analog pins, so a DVI-A cable cannot be used on a DVI-D only port.
Adapters exist to join different connectors, such as DisplayPort to HDMI. Converting digital to analog (for example HDMI to VGA) needs an active adapter.
Universal Serial Bus
Universal Serial Bus (USB) connects keyboards, mice, printers, storage and many other devices. The main connector shapes are:
- Type A: the flat rectangular plug on the host side
- Type B: a squarer plug used on printers and some hubs
- Mini and micro: small plugs for older phones, cameras and gadgets
- Type C: small, oval and reversible, usable on both ends of a cable
| Version | Approximate speed |
|---|---|
| USB 2.0 | 480 Mbps |
| USB 3.0 | 5 Gbps |
| USB 3.1 Gen 2 | 10 Gbps |
| USB4 | Up to 40 Gbps |
USB 3 ports are often blue inside, but colour is not a rule. USB is backward compatible, so a faster device on a slower port or cable runs at the slower speed.
Thunderbolt
Thunderbolt 3 and Thunderbolt 4 use the USB-C connector and reach 40 Gbps; later versions are faster. They can carry data, video and power. A Thunderbolt port works with ordinary USB-C devices, but a plain USB-C port may not support Thunderbolt devices.
Drive cables
| Cable | Use |
|---|---|
| Serial Advanced Technology Attachment (SATA) | Connects internal drives to the motherboard; the common internal drive interface |
| eSATA | An external version of SATA, now rare |
| Integrated Drive Electronics (IDE), also called Parallel Advanced Technology Attachment (PATA) | Old wide ribbon cable for older drives |
| Small Computer System Interface (SCSI) | Older standard for drives and other devices, now rare |
SATA uses a thin, flat cable with a small L shaped data connector. A separate power cable also goes to the drive. SATA version 3 runs at 6 Gbps.
Serial and other older connectors
- Serial port (DB-9): an older nine pin D shaped connector for modems, network gear consoles and some industrial devices. It follows the Recommended Standard 232 (RS-232).
- Personal System/2 (PS/2): a round six pin connector for keyboards (purple) and mice (green) on older computers.
- Lightning: an Apple connector on older iPhones and iPads.
A cable that carries audio and video in one connector is HDMI or DisplayPort. VGA and DVI-D carry only video.
Choosing a cable
Pick the newest connector that both devices share. A 4K monitor at a high refresh rate generally needs DisplayPort or a current HDMI version. A cable that is too old may leave the picture at a lower resolution or refresh rate.
What to remember for the exam
- VGA is analog and carries video only; HDMI and DisplayPort carry digital video and audio.
- DVI-D is digital only, DVI-A analog only and DVI-I both.
- USB 2.0 is 480 Mbps, USB 3.0 is 5 Gbps and USB 3.1 Gen 2 is 10 Gbps.
- USB-C is reversible; Thunderbolt 3 and 4 use USB-C and reach 40 Gbps.
- SATA is the usual internal drive cable; IDE is the old ribbon type.
- PS/2 keyboards are purple and mice are green.
- Serial ports use a nine pin DB-9 connector.
- Backward compatibility means the slowest part sets the speed.
Common mistakes
Assuming every USB-C port does everything. Some carry only data, with no video or fast charging.
Using the wrong DVI cable. A DVI-A cable cannot connect to a DVI-D only port.
Expecting audio through VGA. VGA carries video only, so audio needs a separate cable.
Mixing up SATA and IDE. SATA is thin and serial; IDE is a wide ribbon.
Forgetting adapters change signal type. Digital to analog conversion needs an active adapter, not just a plug shape change.
Check yourself
Which two video connectors carry both digital video and audio?
HDMI and DisplayPort.
What speed does USB 3.0 run at?
About 5 Gbps.
Which connector type is analog and carries video only?
Video Graphics Array (VGA).
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