DisplayPort 1.2, 1.4 and 2.1: Versions and Cables

DisplayPort versions are defined by the VESA standard, and the version number tells you the link rate, not what a cable can do. DisplayPort 1.0 arrived in 2006; DP 1.2 raised the link to 21.6 Gbps (HBR2) and added MST daisy-chaining; DP 1.4 raised it to 32.4 Gbps (HBR3) and added DSC compression, enough for 4K at 120 Hz and 8K at 60 Hz with DSC; DP 2.0 and 2.1 define three UHBR rates - UHBR10 at 40 Gbps, UHBR13.5 at 54 Gbps and UHBR20 at 80 Gbps. A cable is certified by the rate it passes, not by a version number printed on the bag.

What each DisplayPort version carries

DP 1.4 is the version most desktops, laptops and monitors actually implement. It is the one to look for when a monitor needs 4K at 120 Hz or 8K at 60 Hz, and it does that with DSC, DisplayPort’s display stream compression. DSC is visually lossless compression applied to the link, not to the file; the monitor decompresses it. Without DSC, DP 1.4 carries less than the headline rate suggests, because the raw pixel rate of high-resolution, high-refresh video is large.

DP 2.0 and 2.1 are the same electrical specification under two names, with 2.1 adding management and cable-related refinements. UHBR20 at 80 Gbps is the top rate. A monitor and a graphics output must both support the UHBR rate in use; a DP 2.1 monitor on a DP 1.4 port falls back to HBR3.

DSC and MST

DSC, defined in the DisplayPort standard, compresses the video stream so a given link can carry more pixels. It is what makes 4K at 120 Hz and 8K at 60 Hz possible on DP 1.4. Both ends must support it; if the monitor does not, the source drops to an uncompressed mode with a lower resolution or refresh rate.

MST, multi-stream transport, arrived with DP 1.2. It lets one DisplayPort output drive several monitors from a single link, either through a hub or by daisy-chaining monitors that have a DisplayPort output of their own. The total pixel budget is shared, so two 4K displays at a high refresh rate can exceed what one HBR3 link carries. MST hubs and daisy chains also depend on the monitor’s own MST support; a monitor with only an input cannot pass the stream on.

Which cable for which rate: DP8K, DP40, DP80, DP80LL

VESA certifies DisplayPort cables by the link rate they are built and tested for:

A DP8K cable is the right choice for a DP 1.4 monitor. A DP40 or DP80 cable is what a DP 2.1 monitor and card need to reach UHBR rates. Buying a DP80 cable for a DP 1.4 link is harmless but unnecessary; buying an uncertified cable for an 80 Gbps link is where intermittent blanking and link drops come from. Passive DisplayPort copper cables lose margin as length and rate rise, so a long run at UHBR20 is harder than the same length at HBR3. DP80LL exists for exactly that reason.

When a monitor needs 4K at 120 Hz, the chain is: a source that supports HBR3 or better, a DP8K (or higher) cable, and a monitor that accepts the rate. If any part of that chain is a DP 1.2-era cable, the link negotiates down and the refresh rate drops with it.

Mini DisplayPort and the connector family

Mini DisplayPort is the same signal on a smaller plug. It appears on older laptops, on some small form-factor machines and on adapters. A Mini DisplayPort to DisplayPort cable is a passive cable: the wires run straight through, and no converter chip is involved. The same is true of Mini DisplayPort to HDMI or DVI only where the source port supports DP++.

DP++ (dual-mode) ports can drive HDMI or DVI through a passive adapter, because the port itself emits the required signalling. A port without DP++ needs an active adapter with a converter chip. This is the single most common adapter mistake: a passive HDMI adapter on a non-DP++ port gives no picture at all.

DisplayPort Alt Mode carries DisplayPort over USB-C. The video signal travels on the USB-C cable’s high-speed lanes, so the cable must be rated for the data rate involved. That is where the connector-versus-cable confusion bites: see why USB-C cables are not all the same before assuming any USB-C cable will carry a high-rate DisplayPort signal to a monitor.

Choosing between DisplayPort, HDMI and USB-C output

DisplayPort and HDMI overlap heavily at 4K, and the choice usually comes down to which port the monitor and the computer both have, and which features are needed. The comparison of rates, audio return and multi-display behaviour is covered in HDMI vs DisplayPort: which to use.

USB-C and Thunderbolt outputs are the other route to a monitor, and the cable matters as much as the port. A Thunderbolt 4 or 5 cable also works as a USB-C cable for data and charging, and Thunderbolt 5 runs 80 Gbps both ways with up to 120 Gbps in one direction for displays. The differences between the two families are set out in Thunderbolt 3, 4 and 5 vs USB4.

What goes wrong

• A version number on the packaging is not a rate. DisplayPort cables are certified by rate - DP8K, DP40, DP80, DP80LL - and a cable sold only as “DisplayPort 1.4” may not have been tested for HBR3. Match the certification to the link rate.
• A passive HDMI or DVI adapter on a non-DP++ port. No picture. Check whether the port is dual-mode before buying a passive adapter; otherwise use an active one.
• MST budgets are shared. Two high-resolution displays on one daisy chain can exceed the link, and the source drops the refresh rate or refuses the second display. Add up the pixel rate before assuming a chain will work.
• DSC needs both ends. A monitor without DSC cannot use the compressed mode, so 4K at 120 Hz or 8K at 60 Hz may not be available even though the cable and card support it.
• Long passive cables at high rates. At UHBR20, cable length is the limiting factor. A short certified cable is more reliable than a long uncertified one.
• USB-C cables are not interchangeable. A USB-C cable may be a USB 2.0 cable at 480 Mbps or carry 10, 20, 40 or 80 Gbps. DisplayPort Alt Mode over a charge-only cable will not drive a monitor.
• Adapters that convert the wrong direction. DisplayPort to VGA needs an active converter, because VGA is analogue. DisplayPort to DVI or HDMI can be passive only with DP++.

Matching the cable to the job

For a 4K monitor at 60 Hz on a DP 1.2-era machine, a standard DisplayPort cable is usually enough. For 4K at 120 Hz or 8K at 60 Hz with DSC, use a DP8K cable and confirm the monitor supports DSC. For a DP 2.1 card and monitor at UHBR20, use a DP80 or DP80LL cable, and keep the run as short as the layout allows. For a laptop with Mini DisplayPort, a passive Mini DisplayPort to DisplayPort cable is the simplest answer; for HDMI output from that port, check DP++ first.

Label both ends of every cable, and keep the certification of each one known. When a link drops to a lower resolution or refresh rate than expected, the cable and the adapter are the first two things to swap, before assuming the graphics output or the monitor is at fault.