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I have a MacBook pro which has 2 thunderport 3 ports. It connects to a HDMI monitor via HDMI cable, an ASUS ZenScreen MB16ACM which connects via usb-c.

I want to use the ZenScreen in portrait mode so I can only use the usb-c port, not the usb-a adapter. The other screen is using a usb-c hub to connect to HDMI. So if I use both screens I cannot charge the MacBook.

Is there a MacBook docking station which is able to:

  1. charge my MacBook via thunderbolt
  2. output video to usb-c screen ZenScreen
  3. output video via HDMI

So I only need to connect my MacBook with the station by 1 cable, and the station would output video to both screens?

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Yes, but they're expensive; you may want consider alternatives

Interfaces and protocols

To understand why this is kinda a pain, we need to understand what's actually going on when we connect a monitor up to the various ports available to us. I've talked about this a bit before, but that focused on a slightly different case, so it's worth re-writing here.

USB-C

USB-C is a specification for a physical connector type (like USB-A, USB-B, mini USB, and micro USB), not a protocol in itself. While the physical connector does allow/limit what can be carried, it does not in itself specify what is carried. USB-C can carry (or not carry) USB data (ranging in speeds from 2.0's 380 Mb/s to 4.0's 40 Gb/s (upcoming)), power, or any one of the display-oriented "Alternate Modes" (DisplayPort, MHL, HDMI, and confusingly, Thunderbolt Alternate Modes respectively.) These alternate modes are how most inexpensive USB-C dongles work, as they allow almost entirely passive operation. Even dongles such as Anker's 7-in-1 that have separate power passthrough and data ports still use this mode, using a sort of internal USB hub to support the multiple USB devices while directing display functionality to the HDMI port. As a consequence, the data port on these devices cannot be used to output separately to another display, as the alternate modes only carry signaling for a single display (more on that later.) While you may be able to get the displays to mirror, they definitely won't act as separate displays.

Thunderbolt

Thunderbolt is... complicated. However, for the purposes of what we're doing, we can focus on a few main things. First, unlike USB, Thunderbolt supports daisy chaining for up to six devices; however, it does not support hubs. Second, although Thunderbolt 3 uses the USB-C port, it does not use the alternate modes to carry video, and instead embeds its own DisplayPort stream alongside the "main" PCI-e data stream. As a result, we can use a Thunderbolt hub with multiple displays. Unfortunately, the hardware required to support these devices is way, way more expensive; the specialized nature doesn't help costs either.

Aside: USB 4 is effectively Thunderbolt, but handled by a different standard organization. Since your particular computer has Thunderbolt, I'll be using the term here, but you can consider them to generally be interchangeable.

In terms of options, I'd recommend either the OWC 14-Port Thunderbolt 3 Dock, the Cable Matters Thunderbolt 3 Dock, or one of Kensington's various docks (potentially the SD5300T, as it's the cheapest and has requires no HDMI adapter.) They're all about $200, and they all fit the basic requirements (charging, HDMI/DP and USB-C video output), so it's just a question of what extra features you want (max power delivery, audio out, number of Thunderbolt ports, number of USB ports, SD connectivity, Ethernet, etc.

It's at this point thought that you might notice that the video outs on these hubs vary a bit—yet they all say they support HDMI, even if they have no physical HDMI port. It's time to talk about...

DisplayPort

DisplayPort is a video interface connection and the underlying video carrier for Thunderbolt and most USB-C-only displays. DisplayPort also contains two important features:

  • DisplayPort++, where a the output device changes what it's outputting to effectively an HDMI signal, allowing a passive adapter to easily and cheaply convert the signal to HDMI (or DVI.) Sound familiar? This is very similar to how USB-C alternate modes work. Be careful though: they are not the same thing, and are not even interoperable. Even though USB-C has a DisplayPort alternate mode, because of the limitations of the physical USB-C connector, the DisplayPort alternate mode does not support DisplayPort++. Confusing, right? Let's run through some things to (hopefully) help make sense of this:
    • USB-C non-Thunderbolt → DisplayPort: works (uses DisplayPort alternate mode)
    • USB-C non-Thunderbolt → HDMI: works (uses HDMI alternate mode)
    • USB-C non-Thunderbolt → DisplayPort → HDMI: does not work, unless you use an active DisplayPort to HDMI adapter
    • Thunderbolt (any revision) → DisplayPort: works (Thunderbolt contains DisplayPort signal)
    • Thunderbolt (any revision) → DisplayPort → HDMI: works (uses DisplayPort++)
    • Thunderbolt 3 → USB-C → DisplayPort/HDMI: works (uses alternate modes)
  • MST, where a single DisplayPort signal can be multiplex to support multiple monitors via use of a hub. However, this feature is not supported in macOS, meaning certain hubs like the HP Thunderbolt 3 G2 can only use one of their dedicated DisplayPort outs. Note that this is a software limitation, not a hardware one; if you use another OS on your laptop, MST should work.

So what does this matter? Well, the first means that any can use a DisplayPort port (including Mini DisplayPort) or Thunderbolt port as an HDMI output; if the dock you want doesn't have HDMI, don't fret. The second means you'll need to be careful choosing, as you'll only have a maximum of two display outputs (one HDMI/DisplayPort/USB-C and one daisy-chained Thunderbolt.) Basically, you'll need at a minimum need 1x USB-C out (for your portable display) + 1x HDMI/DisplayPort out (for you normal display.) Some example configurations that would work:

  • 1x Thunderbolt 1/2 out + 1x USB-C out
  • 1x Thunderbolt 3 + 1x USB-C, HDMI, or DisplayPort
  • 1x USB-C + 1x HDMI or DisplayPort

DisplayLink

I know you already mentioned that you don't want to use this, and I agree—albeit for different reasons. Still, it's worth going over.

DisplayLink, unlike the other things mentioned, uses a software solution to push a display signal over a normal USB interface. While this does solve the need to get another dedicated display signal and would allow you to use a cheap adapter like the Anker one linked earlier, DisplayLink comes with some annoying restrictions:

  1. You need a driver, which requires the OS to be up and running correctly as well.
  2. The performance, while not awful, isn't good. Lag (in my experience) is very noticeable even in day-to-day use, in the multiple 100ms range.

While I'm sure the orientation problem is fixable, these issues are not. As such, I'm going to agree that staying away from DisplayLink—even though the cost is very minimal due to the included solution—is a good idea.

eGPU?

Sidenote: I'm assuming you have an Intel based MacBook Pro, as Apple Silicon devices currently don't support eGPUs.

Given how expensive these Thunderbolt hubs are, there's one other option. Basically, an eGPU is just an external graphics card connected over Thunderbolt. This has some advantages and disadvantages:

Pros:

  • More power to increase your performance in graphics-heavy workloads, such as gaming or 3D modeling.
  • The ability to connect more displays (as many as your graphics card can support) without the need for MST (which, again, isn't supported on macOS.)

Cons:

  • More expensive (~$150-250 for an enclosure + the cost of your chosen graphics card)
  • More power consumption/potentially extra noise, since you're powering a graphics card

However, in your particular case, there's an additional complication: the USB-C port on your monitor. Unfortunately, most graphics cards don't have a USB-C port. There are a few cards which implement VirtualLink, a proposed USB-C alternate mode that isn't quite the same as the other standardized Alternate Modes, but from a practical standpoint, is often largely compatible. So far though, the only graphics cards with USB-C ports are select Nvidia RTX 2000 and AMD Radeon RX 6000 cards. Unfortunately, Nvidia cards haven't been compatible with macOS since High Sierra (before the 2000 series debuted), and all RX 6000 series cards are out of stock everywhere due to supply issues. Additionally, the RX 6800, the cheapest compatible card currently available, retails for $579, with scalpers currently asking $850+. Yikes.

Still, if you can benefit from the performance and if you're willing to either wait for cheaper cards or pay the price, I'm going to recommend getting an eGPU. Between the increased performance and additional outputs, it offers a much better upgrade path—assuming Apple adds eGPU support for Apple Silicon. Given the limitations though, I understand if that's not your ideal path.

Buy another monitor?

Stupid as it may sound, you can get a pretty reasonable monitor for $200. Unless you have a real love for your ZenScreen, you may be better off getting another monitor—either a desktop one, or a different portable one.

In terms of other portable displays, I see two main options: 1. Get another dedicated display that has the option for separate power and data channels (likely USB-C for power and HDMI for data). 2. Get an iPad and use Sidecar (or, if you want to use an older model, Duet Display.) Again, I'm going to dismiss using a DisplayLink monitor for the reasons outlined earlier.

Two cables

Okay, yeah, this one is really dumb. Still though, it'll get you the full performance while costing next to nothing, since all you need is a cheap passive USB-C dongle with HDMI and power passthrough—of which there are tons. Yes, it's not as elegant having one cable go to the ZenScreen and one to everything else, but when faced with the proposition of spending $200, maybe it's an okay trade-off.

Conclusion

First, props for reading this whole thing; I know it's a long one, but unfortunately, this stuff is kinda a mess. Unfortunately, the standard are complicated, and everyone made different trade-offs with different goals in mind. What exactly is the right solution for you is going to vary; however, I hope this can at least set you on the right path. If you have any further questions, please feel free to leave a comment and I'll be happy to help more.

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