Is It Possible to Use Plugged Well Again?

USB-C offers exciting new capabilities, including external monitors connected through the USB port. USB-C converters to DisplayPort or HDMI are common and inexpensive. USB-C hubs with external monitor support are as well mutual, but understanding their capabilities and limitations can exist extremely confusing. Some are Mac-compatible and some aren't. Some need driver software. Supported resolutions and refresh rates vary widely. Some are advertised as "not for gaming apply". In that location are mentions of alt manner and dual mode and more. Prices range from $20 to over $300 for what look similar very similar features. What'due south going on here?

This is the guide to high-resolution video over USB-C that I wish I'd had. If you lot're hoping to connect a high-res external display to your USB-C equipped computer, read on.

October 2020 Update: see the notes at the end of this commodity about how DisplayPort ane.4 changes the landscape.

Forget About HDMI

Lesson 1 is to focus on DisplayPort video connections, and forget about HDMI. Y'all'll never find a USB-C hub that offers better video capabilities through its HDMI port than through its DisplayPort, but you will find hubs that offer better DisplayPort resolution and refresh rates. I strongly suspect most hubs with an HDMI port are actually implemented internally as a DisplayPort, with an integrated DisplayPort to HDMI converter. This is because DisplayPort video can be carried more than efficiently on the USB-C connection than HDMI for the same resolution and refresh charge per unit.

DualMode DisplayPort++ connectors are able to role as HDMI connectors with a simple passive adapter (it does 3.3V to 5V level conversion). Regular DisplayPort connectors can't do this, and require an active HDMI adapter with more built-in smarts. Otherwise I'k not enlightened of any difference between these two DisplayPort types.

Bandwidth Tradeoffs – It's All About The Lanes

The 24 pin USB-C connector is the key to understanding. The diagrams beneath are from techdesignforums.com.

USB-C connectors have iv differential pairs called "lanes" for carrying high speed data. In that location'due south also a fifth differential pair D+ and D-, that carries former-style USB 2.0 data.

Let's look at what happens when DisplayPort is added into the mix:

USB three.1 Gen 2 merely uses two of the 4 lanes, as shown in the top two rows of this table. The other two lanes are substantially wasted (they volition be used by USB 3.2). These ii lanes can be repurposed to carry a native DisplayPort indicate, using what's called DisplayPort Alternate Mode, as shown in the middle table rows. In this case the USB-C connector functions like a DisplayPort connector with a dissimilar shape and some extra wires for USB data. There's no loss of USB iii.one performance. To the figurer and the external monitor, this looks exactly like a regular DisplayPort connection.

Ii lanes for DisplayPort provide enough bandwidth for one external monitor at up to 4K 30Hz. That's OK for watching movies, but a 30 Hz Windows or MacOS desktop experience is painful. To continue a threescore Hz refresh charge per unit, y'all need to pace down to 2K or lower resolution.

If you want 4K 60Hz, 5K, or multiple external monitors, then you'll need to use DisplayPort Alternating Mode with all four lanes for DisplayPort data, as shown in the bottom rows of the table. To the figurer and the external monitor, this all the same looks exactly like a regular DisplayPort connection. Only at present there are no lanes remaining for USB 3.1 data. There'due south merely the quondam D+/D- pair providing slower USB 2.0 information. That ways any USB-C hub using this technique for 4K60 video can't accept any USB 3.1 ports on information technology.

External DisplayPort monitors can also be supported using zero dedicated lanes for DisplayPort Alternate Fashion, with 1 of two approaches. If the calculator's USB-C port has Thunderbolt 3 capability, and then DisplayPort data can be encapsulated inside the Thunderbolt data stream. The video data becomes but 1 more type of packetized data multiplexed with everything else. Thunderbolt 3 has enough bandwidth to support multiple 4K60 video connections this way, with enough bandwidth remaining for USB 3.1 information too.

This is keen, but Thunderbolt iii hubs are expensive, and the reckoner must have Thunderbolt iii capability, and many computers don't. This also looks unlike to the estimator – unlike DisplayPort Alternate Mode, in that location are no native DisplayPort signals and no straight connexion to the computer's GPU. It's not clear to me whether in that location'south a performance penalty for treating video this way, or if information technology's all handled magically by the chipset with no loss of functioning. My hunch is at that place'southward no operation penalty. If you know more, please tell me.

DisplayLink

The other method of supporting external monitors with aught dedicated lanes is DisplayLink. This applied science compresses the video data on the host side, sends it over a USB 3.i connectedness as generic data, and reconverts it to video on the other end using a special chip like the DL-6950. Conceptually it's like a remote desktop connexion for sharing your work calculator's screen when you're logged in from home, except everything happens locally on your desktop.

DisplayLink is nice for squeezing high-resolution video over a lower-bandwidth connexion like USB, or for supporting multiple high-res external monitors without Thunderbolt. But if you have any alternative, I remember DisplayLink is best avoided. Here are some disadvantages:

• Host-side driver software is required. Commuter availability and compatibility for Mac/Linux is spotty to non-existent. This is why some USB-C hubs are advertised equally not Mac-compatible.
  
• The driver software can slow your computer. It implements a virtual graphics card performing on-the-fly compression of video information, which adds some CPU overhead.
  
• When the reckoner is very busy or at that place'southward a lot of other USB traffic, video artifacts volition appear. Yous'll see pixelation, stuttering, frame dropouts, and other problems. This is why some USB-C hubs are advertised every bit "not for gaming use".

USB-C hubs utilizing DisplayLink piece of work fundamentally differently than the others, but yous probably wouldn't realize that from reading the product descriptions and technical specs on Amazon or Newegg. If you don't know what you're looking for, information technology's piece of cake to buy a DisplayLink-based hub without realizing it, and endure its shortcomings unnecessarily.

TL;DR – What are the Options?

Putting all this knowledge together, we can group USB-C hubs into iv categories based on how they treat video. Here are some examples in each category.

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four Lanes for Video

These support external monitors up to 4K60, or possibly 5K, but can but provide USB ii.0 information. That's not the fastest, but information technology's enough for keyboards and mice and bones printers. They should piece of work on any computer that supports DisplayPort Alternating Mode, and typically cost around $30.

Cable Matters 201046 – 1x DisplayPort, ability, ethernet, 1x USB2
Cable Matters 201055 – 2x DisplayPort, power, ethernet, 2x USB2
Monoprice 24274 – 1x DisplayPort, power
Cable Matters 201026 – 1x DisplayPort, power
Baseus B07P713FPD – 1x DisplayPort, power

2 Lanes for Video

These support external monitors up to 4K30 besides as USB 3.1 information. Many are advertised as simply "4K" without mentioning the refresh rate. They should piece of work on any estimator that supports DisplayPort Alternate Mode, and typically cost around $thirty-$150.

HooToo HT-UC001 – 1x HDMI, 3x USB3, power, carte du jour reader
OmniMaster B07KRMRJZD – 1x HDMI, 1x mini DisplayPort, power, ethernet, 2x USB3, carte du jour reader, mic
Anker AK-A83310A1 – 1x HDMI, 3x USB3, ethernet
Vava VA-UC006 – 1x HDMI, 3x USB3 Ports, power, ethernet, card reader
StarTech DK30C2DAGPD – 2x DisplayPort (switchable 2 or 4 lanes), power, ethernet, 2x USB2/3

0 Lanes for Video – DisplayLink

These back up multiple external monitors upwardly to 4K60, or perhaps 5K, besides as USB iii.ane information. But they generally are simply uniform with Windows computers, not Macs or Linux machines, and they take other performance drawbacks. They cost around $150-$200.

Plugable UD-3900 – includes 1x HDMI, 1x DVI
Plugable UD-ULTC4K – includes 2x DisplayPort, 1x HDMI
Plugable UD-6950H – includes 2x DisplayPort, 2x HDMI
SIIG JUDK0811S1 – includes 2x DisplayPort, 2x HDMI

0 Lanes for Video – Thunderbolt 3

These support 2 external monitors upwardly to 4K60, or possibly 5K, also equally USB three.1 data. They should work on whatsoever figurer that has Thunderbolt 3 support. They are the most expensive selection, with a typical price effectually $250 to $300.

OWC OWCTB3DK12PSG – includes 1x mini DisplayPort, 1x Thunderbolt display
Plugable TBT3-UDV – includes 1x DisplayPort, 1x Thunderbolt display
Cable Matters 107014 – includes 1x HDMI, 1x Thunderbolt display
Kensington SD5200T – includes 1x DisplayPort, 1x Thunderbolt brandish
Elgato 10DAA4101 – includes 1x DisplayPort, 1x Thunderbolt display
Belkin F4U095tt – includes 1x DisplayPort, 1x Thunderbolt brandish
CalDigit TS3 – includes 1x DisplayPort, 1x Thunderbolt display

Deceptive Descriptions

Finally, we have an interesting category of off-brand USB-C hubs costing around $30 that claim 4K60 video support and USB3.i data support. Search Amazon and you'll detect quite a few of these. Based on knowledge of USB-C and DisplayPort, nosotros at present know this is impossible without using DisplayLink or Thunderbolt three. These products are all lying about their capabilities! They are very likely DisplayPort Alternate Mode designs using four lanes. They may take blue USB ports labeled "USB 3.ane", but equally many of the reviews attest, they only provide USB 2.0 data speeds.

Clarification: See the annotate below from Jan. Some of these hubs may support 4K60 video or USB3.1 data, merely non both at the same time.

Koopman B07J4XSSXV – 1x HDMI, power, 1x USB
WBPINE HUB3-1 – 1x HDMI, power, 1x USB
Koopman B07M5DMYKY – 1x HDMI, power, 3x USB
NEWPOWER B07PQ5GZK1 – 1x HDMI, ability, 3x USB

What's been your experience with external monitors continued by USB-C? Leave a note in the comments.

DisplayPort ane.4 Update (October 2020)

The USB-C video options were already very disruptive, and now they're even more so. The analysis above is correct for DisplayPort 1.2 devices, which were the most common blazon at the fourth dimension I wrote this article. My current computer and monitor utilize Display Port one.2, and yours probably do too.

DisplayPort one.4 was introduced in 2016, just products with DP1.4 didn't become widespread in the marketplace until roughly 2019. Now that DP1.4 back up is condign more common, the landscape for 4K60 USB-C video has changed.

DisplayPort ane.four tin can deliver 4K 60Hz video using only two lanes, with a new high-scrap-charge per unit mode called HBR3 with a compression mode called DSC. This makes it possible to get 4K60 video and USB 3.i ports in the same hub, just only if the reckoner, hub, and monitor all back up DisplayPort 1.four and HBR3.

Shopping for compatible equipment tin be a challenge, because the DisplayPort version isn't always advertised. For example, this Anker PowerExpand A8383 hub is ane that should support simultaneous 4K60 video and USB3.i data, but the words "DisplayPort" or "1.4" don't appear anywhere in the text of Amazon's item clarification. One of the product photos contains some (non-searchable) text that says "please confirm your device supports DP 1.4", just it's very piece of cake to miss. The manufacturer's spider web site does mention DP1.iv in the text, but it'southward style down the page in a troubleshooting footnote. So you may need to dig through the technical specs or download the transmission in order for confirm DisplayPort ane.4 support when buying a new hub, computer, or monitor.

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Source: https://www.bigmessowires.com/2019/05/19/explaining-4k-60hz-video-through-usb-c-hub/

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