Info Update on DisplayPort cable certifications

NOTE: This is a copy of an old thread. I originally posted this on July 4, 2019, shortly after version 2.0 of the DisplayPort Standard was released. Due to a forum software bug it is being hidden from public view on its own. I have discussed it with forum staff, but the thread keeps hiding itself for no reason. As a result, I am re-posting it again.

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This post is about DP cables in the new landscape of DisplayPort 2.0. This post is intended for the permanent member base here, just to keep everyone on the same page as far as DP cable ratings are concerned.

What We Already Had — DisplayPort 1.4 and Earlier

Up to this point, DisplayPort has four different transmission speeds:​
  • Introduced in version 1.0:
    • RBR — 6.48 Gbit/s — Introduced in version 1.0, good for up to 1080p 90 Hz
    • HBR — 10.8 Gbit/s — Introduced in version 1.0, good for up to 1080p 144 Hz or 4K 30 Hz
  • Introduced in version 1.2:
    • HBR2 —21.6 Gbit/s — Introduced in version 1.2, good for up to 1080p 240 Hz or 4K 60 Hz
  • Introduced in version 1.3:
    • HBR3 — 32.4 Gbit/s — Introduced in version 1.3, good for up to 4K 120 Hz
Versions 1.1, 1.1a, 1.2a, 1.4, and 1.4a did not introduce any new transmission speeds.​
Cables only affect the maximum transmission speed. Cables do not affect anything else (i.e. support for features, such as HDR or FreeSync/G-Sync). Since some versions of the DisplayPort standard introduce more than one transmission speed, and other versions don't introduce any, it doesn't make any sense to classify DisplayPort cables by "version number". That is why VESA doesn't classify DisplayPort cables by "version number".​
DisplayPort cables are classified by their maximum transmission speed. There are no "DP 1.2 cables" and "DP 1.4 cables". There are DisplayPort cables rated for HBR2 speed, and there are DisplayPort cables rated for HBR3 speed. Since some cable manufacturer are dishonest and you can't take their word about what speeds their cables can support, VESA has a certification program for DisplayPort cables, so that they can be independently tested and certified to operate at a certain speed. These are the current DisplayPort certifications:​
  • Standard certified DisplayPort cable — These cables are certified to handle at least HBR2 speed (4K 60 Hz, 1440p 165 Hz)
  • DP8K certified DisplayPort cable — These cables are certified to handle at least HBR3 speed (4K 120 Hz, 1440p 240 Hz)
People may often tell you "any DisplayPort cable can handle any speed; there are no different ratings for DP cables". This is incorrect. They will often cite this article written by the then-chairman of VESA, which says:​
A standard DisplayPort cable is designed to work with any DisplayPort Source device, such as a PC or laptop, and any DisplayPort monitor. This means that a standard DisplayPort cable will work with the very first DisplayPort systems and displays introduced around five years ago, and they will continue to work with the newest and future systems and displays that support multi-stream and display resolutions up to 4K (Ultra HD) at 60Hz. You can also use a standard DisplayPort cable between a PC and a multi-stream hub, or between daisy-chainable multi-stream monitors. You don’t need worry about getting a special cable to support certain DisplayPort capabilities.

[...]

Despite what you may read, there is no such thing as a DisplayPort 1.1 cable and DisplayPort 1.2 cable. A standard DisplayPort cable, including the so-call DisplayPort 1.1 cables, will work for any DisplayPort configuration including the new capabilities enabled by DisplayPort 1.2, including 4K and multi-stream capabilities.
This leads people to repeat "any DP cable can handle any DP speed". This was true at the time the article was written; since DisplayPort 1.2 was the latest version, HBR2 was the highest transmission speed, and all certified DisplayPort cables can handle HBR2 speed. However, HBR2 is no longer the highest transmission speed in DisplayPort, and standard certified DisplayPort cables are not guaranteed to handle HBR3 or above. You will note that the article has since been removed from the VESA website (hence the archive link provided above). To handle HBR3 speed, the DP8K certification was introduced in 2018, which clearly would be unnecessary if the existing Standard Certification guaranteed proper operation at this speed.​
That is a summary of the situation leading up to the release of DisplayPort 2.0. Four transmission speeds (RBR, HBR, HBR2, and HBR3), and two cable certifications levels: DP8K certified (for HBR3 speed), and Standard certified (for HBR2 speed and below).​


Changes in DisplayPort 2.0


Relevant information:

DP cable design and wiring has not been changed. Just as before, all DP cables are compatible with all DP devices, but what can differ between cables is the maximum speed it can handle, and therefore the maximum resolution/refresh rate that will be available.​
On top of the previous HBR3 speed (32.4 Gbit/s) introduced in DP 1.3 and used also by DP 1.4, DisplayPort version 2.0 introduces three new transmission modes (these are the signaling speeds that the interface can operate at; not talking about cables yet):​
  • UHBR 10 — 40 Gbit/s — (Good for up to 4K 144 Hz uncompressed)
  • UHBR 13.5 — 54 Gbit/s — (Good for up to 5K 120 Hz uncompressed)
  • UHBR 20 — 80 Gbit/s — (Good for up to 8K 60 Hz uncompressed)
There are no new cable certifications for these modes. The DP8K certification (released in Jan. 2018 to certify cables for HBR3 speed) was supposedly designed with foresight to be sufficient for UHBR 10 speed as well. Cables that have passed the DP8K certification (cables certified for HBR3 speed) should also be able to handle UHBR 10 speed.​
For UHBR 13.5 and 20 speeds, VESA has not publicly introduced any certifications for box-to-box (standalone) cables. These speeds are very difficult with normal passive cables, and will likely require amplified cables (or optical cables with transceivers on each end), which are expensive, for anything but the shortest distances. VESA is encouraging displays to use a tethered cable (captive/non-detachable) for UHBR 13.5 and 20 speeds, with any necessary active circuits built in, to guarantee that the cable has sufficient capability, and also likely avoid the stigma of "requiring expensive cables" that has plagued Thunderbolt 3 (of course it doesn't actually eliminate the cost, it simply hides it by building it into the price of the monitor instead). But in any case, there are no publicly announced certifications for UHBR 13.5 or 20 speeds, so it would appear that VESA will not be giving any certifications for box-to-box cables beyond DP8K (HBR3 / UHBR 10). Any claims of "UHBR 13.5 / UHBR 20, 80 Gbit/s certification" etc. are therefore false claims, as VESA does not currently certify standalone cables for these speeds.​
I have no doubt there will be cables available very soon advertised as "DisplayPort 2.0 certified". Such claims are meaningless, since UHBR 10 uses the same certification as HBR3 (DP 1.3/DP 1.4 max speed), and there are no certifications being given for UHBR 13.5 or UHBR 20 speed for standalone cables at this time. But unfortunately, lying about cable certifications is very common practice. As a cautionary tale: within days of the HDMI 2.1 specification being published, there were "Ultra High Speed HDMI cables" being sold by major brands like Belkin, despite the fact that the CTS for HDMI 2.1 (the document which describes the Ultra High Speed certification test) wasn't even finished until nearly a year later; they were claiming to be certified when the certification test for that cable category literally hadn't even been written yet, only announced. We can expect the same behavior from cable manufacturers in the wake of DisplayPort 2.0.​
Also note, it remains to be seen whether the captive cable recommendation for UHBR 13.5 and 20 will be followed. If displays are released which utilize these speeds and have an actual DP receptacle, it will be a crapshoot as far as getting cables which can handle these speeds, since certifications are not being given to standalone DP cables for these speeds.​
Relevant quotes from source:
Anandtech said:
At just half the data rate of full-fat DisplayPort 2.0 (and Thunderbolt 3), UHBR 10 is resilient enough that it can operate over standard passive copper cabling, and cables should have little issue reaching 2-3 meters. VESA has actually been preparing for this for some time now, and UHBR 10 aligns with their previously-launched DisplayPort 8K cable certification program; 8K-certified cables will be able to meet the signal integrity requirements for UHBR 10.

Anandtech said:
Past that, however, VESA isn’t currently exploring (or at least not focused on) passive cables for the higher bitrate modes. Instead, the group envisions UHBR 13.5 and UHBR 20 being tethered setups: manufacturers would ship devices with an appropriate port/cable already attached. These can potentially be passive cables for very short runs (think laptop docks), or integrated active cables for longer runs. I should note that the group hasn’t closed the door entirely to more traditional passive cable setups for these higher bitrates, but at least for the moment the group doesn’t see very many non-tethered use cases coming to market in the near future.


Other Clarifications:

Relationship with Thunderbolt 3:
There is a lot of talk about "DisplayPort 2.0 using the Thunderbolt 3 physical layer", and subsequent confusion over whether the traditional DisplayPort connector is being discontinued, if TB3 products will now support DP 2.0, etc. These things are not the case. The use of the TB3 physical layer is a fact that is only of interest from an engineering/design perspective, and has no actual bearing on products or the operation of DP from an external perspective. It is just a detail about how the DP protocol has been changed, and highlights changes to how the high-speed signaling operates under the hood. "Using the TB3 physical layer" does not mean anything from an outside perspective.​
The confusion appears to stem from a misunderstanding, as many people seem to be under the impression that the "physical layer" refers to the connectors. This is not the case. The physical layer is the signal and wiring layout (i.e. design decisions such as twisted pair vs coax, the signaling voltages, what each wire is used for, etc). The cable connectors themselves are typically referred to as the mechanical layer, not the physical layer, at least in these applications.​
The DisplayPort 2.0 protocol (while it operates differently under the hood) still uses 20 pins and will therefore still be compatible with the existing DP / Mini DP design. The USB Type-C connector may also be used. DisplayPort 2.0 is not restricted exclusively to the USB Type-C connector.​
Current Thunderbolt 3 devices will not support DisplayPort 2.0 speeds. DisplayPort 2.0 operates differently than Thunderbolt 3. The use of the TB3 physical layer only means that it is designed similarly in physical layout and how the wires are used, but DP 2.0 uses a different configuration (signaling all 4 lanes in the same direction instead of 2 in each direction), which current Thunderbolt 3 controllers are (AFAIK) not designed to do.​
Anandtech said:
The [full-size DisplayPort connector] itself is staying: it and the USB-C connector (via DP alt mode) are both official ports for the new DisplayPort 2.0 standard.
Transmission Modes, not Version Numbers:
As always, DisplayPort speed capabilities should be spoken of in terms of speeds/transmission modes (i.e. "supports HBR2 speed") rather than versions. This goes for devices (GPUs and displays) as well as cables, adapters, and really anything. While it is common for people to say things like "supports DP 1.2" or "supports DP 1.4" to indicate support for HBR2 and HBR3 speed, this is not recommended, since transmission speeds and "version numbers" do not really align. It may be convenient that certain versions only introduce one new speed (like DP 1.2 introduced HBR2, and DP 1.3 introduced HBR3), so it is easy to use the two interchangeably, but these things are not necessarily coupled.​
Even the very first version, DP 1.0, introduced two speeds: RBR and HBR, and this remained the same in DP 1.1. So when someone says "that monitor only supports DP 1.1", what does that mean? Fortunately, the RBR mode was never really used anyway (except on displays that were spec'd below that level anyway), so that distinction never mattered, but with DP 2.0 introducing three new speeds, we really can no longer keep using version numbers to indicate transmission speeds.​
As a quick reference, when people say:​
  • "DP 1.1 speed", they are typically referring to HBR speed
  • "DP 1.2" --> HBR2
  • "DP 1.3" or "DP 1.4" --> HBR3
Consider adjusting your notation habits accordingly 👍​
 
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