Gaslighting discussion (split from: Justin’s Miscellaneous Posts)

I’m debating setting up my M1 MacBook Air for multiple external displays with something like this

Reason: My iMac is performing badly. I have a MacBook Air which performs way way better. I’d like to use the MacBook Air as my primary computer until I replace my iMac, which might not happen for as long as a year depending on what I decide to replace it with. I’m used to having multiple monitors and want that setup. However, the MacBook Air only supports 1 external display natively. You can use DisplayLink adapters to support extra displays. I have 3 external monitors I’d like to use with MacBook Air. So I’d need a DisplayLink adapter that supports 2 adapters + use my MacBook Air’s native 1 monitor out support in order to support 3 monitors.

Multimonitor DisplayLink Adapters are a bit spendy though. And also, this is a somewhat short term purchase - basically it’s enabling me to have a usable multimonitor setup for 6-12 months until I get whatever my next computer is. So I thought I should subject the decision to more scrutiny.

I picked the adapter that I linked because I figured if I was gonna get a 2 DisplayLink adapter to help turn my MacBook Air into a desktop, I might as well go for a full dock that I can plug all my crap into while I’m at it.

I’ve tried using a single external monitor for my MacBook (in clamshell mode) and I don’t like it much. 2 external monitors might work okay, but I have three, so I figured maybe I should try to use all of them.


Oh, I didn’t mention - there’s some performance hit from this DisplayLink stuff, but people say it’s not too bad for a couple of monitors on M1

possibly I shoulda waited for a laptop that supported more external monitors…but OTOH, ultimately I do want a big heavy powerful desktop a light airy laptop so idk

The description / reviews seem unclear to me whether this is a USB-C dock or a Thunderbolt 3 dock, which I’d want to know for sure before buying. I wouldn’t get a USB-C dock[1] at this price point. Some of the reviews make it sound like this is native Thunderbolt 3 but they only include a USB-C cable which you can swap out to actually enable Thunderbolt 3. That’s possible but seems unlikely. I didn’t see anywhere that the manufacturer explicitly says it’s native Thunderbolt, just compatible with Thunderbolt (which is different). So my best guess is this runs at 10 Gbps max on the wire to the Macbook Air, vs. the 40 Gbps your Macbook Air is actually capable of.

The dock I have is:

I’ve had it over 2 years & love it. It’s a true Thunderbolt 3, not a USB-C doc “compatible” with Thunderbolt 3 like I suspect the one you linked is. I routinely run 2 external monitors, Gig-Ethernet, external drives, power, and all USB connections through a single cable to my MacBook Pro just fine. Definitely running 40 Gbps over that wire.

However, I wouldn’t buy it today at least not without a ton of research just because after 2 years there’s almost certainly newer and even better stuff available. I’d probably look for a true USB-4 / Thunderbolt 4 dock though I haven’t researched them.

Another possibility for more displays is Sidecar to an iPad as an extra display. Not good for video and it’s small but it’s an extra display that’s free if you’re not using the iPad for something else at the same time. I do that kind of thing a lot when traveling.

[1] Terminology with USB and Thunderbolt is problematic. There are USB standards like 3.1, 3.2, and 4, then Thunderbolt 3 and 4. They all use the same connector, “USB-C” but they’re different speeds. Higher speed devices and ports will drop down to lower speeds if either end device or the cable between doesn’t support the higher speed. Thunderbolt 3 and 4 as well as USB 4 are 40 Gbps which is what you want for running multiple displays at high refresh rates + all the other ports in the dock. But everything (computer, dock, and cable) must be 40 Gbps capable to achieve that. USB-C 3.1 is 10 Gbps and 3.2 is 20 Gbps. When products just say “USB-C” and nothing else, it’s highly likely they’re running at 10 Gbps. They can say it’s compatible with Thunderbolt 3 because it is - it’ll just drop that 40 Gbps Thunderbolt 3 port down to 10 Gbps. I suppose they could even say you can run 2 4K displays at 60 Hz because you can (maybe - haven’t ever actually tried that) just with a bunch of frame drops.

It seems to be a USB 3.0 dock. I would expect USB 3.0 or 3.1 at that price point given the other relevant features.

Keep in mind a key aspect for me is the support for DisplayLink for outputting to multiple monitors despite lack of sufficient native ports on my current machine. It’s not just a bare USB 3.0 hub. I agree that at that price point, absent DisplayLink, I’d be looking into TBolt hubs over USB hubs (tho the really nice TBolt hubs - CalDigit mb? - actually go for more IIRC)

Haha u literally linked a CalDigit :smiley:

Yaya, I believe u. I’d get something like that if I primarily wanted a high speed hub.

Ya I considered that. I’ve done that kind of thing before. It’s not the same as giant screens tho v_v

Here is a link on how DisplayLink works btw

i felt like i was pretty clear about the importance of DisplayLink in my analysis of potential product purchase. mentioned it by name a few times.

but AndyD didn’t rly engage with that part? idk.

maybe he read it as DisplayPort or something, thought I was talking about something else.

You were not clear originally or in your followup. You have not explained what DisplayLink is or why it matters. And you did not emphasize it or compare it to any alternatives. In your second post you linked to info about it as a “btw” not at something emphasized, and the info you linked is terrible as a relevant summary, so I still have no idea what DisplayLink is, why it matters, or how it fits into this discussion.

Background/problem situation: I have an M1 MacBook Air. The M1 chipset supports two displays. So on an M1 Mac Mini, you can have two external displays. However, on a MacBook Air, which has the same chipset as the M1 Mac Mini, one of the buses or whatever for displays is taken up by the built-in monitor. There appears to be no way to reassign that, even in clamshell mode. So the maximum number of external monitors the MacBook Air can support is 1 external monitor. So if you want to support more than 1 external monitor, you need some sort of workaround like DisplayLink.

Potential solution: DisplayLink names both hardware in certain USB docks and the software drivers that support that hardware, and what they let you do is run more external monitors than you otherwise could. There are other solutions that let you do this for Intel Macs - like display outs in TBolt docks - but my understanding is that their isn’t drivers support for Apple Silicon machines. I have an Apple Silicon machine, so Intel-Mac-only solutions won’t work for me. I think there might be expensive commercial solutions that would work on Apple Silicon machines. AFAIK, DisplayLink is the only affordable, consumer-oriented solution for supporting additional external displays beyond what the system allows that works on Apple Silicon.

Additional details: The number of external displays you can support through DisplayLink is determined by the number supported by your DisplayLink device. These are separate from the number of devices supported natively and don’t count against that total. So, for example, suppose that you have an M1 MacBook Air that supports 1 external display, and you do what I’m considering, which is buying a USB Hub with DisplayLink support that supports two monitors through DisplayLink. The total number of external monitors that you can support is 1 external natively + 2 externals through DisplayLink = 3 external monitors total (which is the number I’d like to use). And on a Mac Mini, because you don’t have the built in display using up a slot, you could support 4 external monitors (2 natively + 2 through DisplayLink).

The MacBook Air only has two USB-C slots, so if you want to have such a 3 monitor setup, I think it makes sense to have a DisplayLink hub, since you’re not going to have any additional free slots to dedicate to power delivery and whatnot. So having one DisplayLink-capable hub that can support power delivery, ethernet, USB connections and so on, makes the most sense to me.

Because of how it works (it’s not an external GPU but closer to an adapter), DisplayLink puts additional load on the system. I have read that this is not really noticeable for ordinary use with a relatively ordinary setup (e.g. 1-2 monitors), though some people do stuff like 6 monitors which seems like it might cause a problem.

Your response is long, doesn’t directly engage with what I said, and doesn’t highlight key points for me. I did not ask for an info dump. I was responding to what you said. You’re responding as if I asked you for certain info in depth when my post was totally different than that.

Also, do you mean that the dock @AndyDufresne has literally won’t work and cannot output to two external displays at once, with an m1 laptop, even though it (the dock) has multiple display output ports? And that DisplayLink is software inside the dock which solves this problem to enable outputting to more monitors? And there are no(?) alternatives that will work? If you mean this idk why you didn’t just say it.

EDIT: Please stop editing your post in response to my post. Even if the changelog showed up – which it didn’t – that’d still be problematic…

I took…

You have not explained what DisplayLink is or why it matters.

… as an invitation to explain what DisplayLink is and why it matters to me. I attempted to provide additional details that seemed relevant to that issue. I find your reply slightly frustrating (I’m not mad or anything though, and I don’t bring that up as a criticism of your reply but as an attempt to be honest about how I’m feeling about the discussion, which seems like a good thing).


Basically yes, with the clarification that DisplayLink is not software inside the dock, but a combination of a supported chipset inside the dock + software you run on your computer.

Less sure about no alternatives, though I haven’t found any yet.

Well it’s what I was trying to get across but I guess I failed.

Off topic: This post is misleading due to a flaw in Discourse.

Justin hit reply to post A and then quoted post B but not post A. This is not clear to readers. There’s nothing showing it’s a reply to post A unless you actually expand what it’s a reply to. If you don’t expand, you’d think it was a reply to the same post (B) that it quoted from. I only noticed what was going on because it doesn’t make sense as a reply to only post B.

I think the best thing to do about this is quote both posts in the future, rather than relying on one as an unquoted parent. And in general to quote text more and rely on only the reply feature less.

EDIT: On a related note, Discourse’s expand parent button works badly because it expands a long chain of discussion and puts you at the top. You then have to scroll down, sometimes quite a bit, to find the direct parent. An obvious solution would be to have two expand buttons. The initial one reveals only the direct parent plus a second button to expand everything else. An alternative solution, that might be adequate, is to expand everything in one click but then set the scroll position at the start of the direct parent not the start of everything expanded.

I decided to add some labels on my own.

You did it minutes after I’d already replied to your post in a way that affected my post.

Do not edit stuff that’s been replied to in ways that matter to the replies, particularly not as a stealth edit with no e.g. EDIT labelling.

Should we drastically reduce the no changelog editing grace?

I’m fine with making an effort to label edits more. That seems reasonable.

You’re gaslighting me.

I disagree that I am gaslighting you. Re: the discussion above, I thought you were still writing your reply when I made my edits. I don’t think you’re lying, though, because that would be ridiculous, so it’s possible I am wrong, didn’t see your reply somehow or something, idk. I think it’d be helpful, in general, if there EDIT: were a clearer objective record of when edits were made (it’d be helpful to me in this instance, cuz I could refer to “the videotape” so to speak, and convince myself about what happened). So I tried to make a helpful suggestion along those lines. I am guessing you took this as maybe implying you were lying or something.

I didn’t know what DisplayLink was. Now I think I do: It’s a software GPU that uses a codec to deliver the display information to an external decoder that then sends it to native display interfaces like DisplayPort or HDMI. Because it uses a codec it can support a higher combination of displays + resolutions + refresh rates than could normally be supported over a link of a given bandwidth. Since it’s a software GPU + codec on the computer side, it places load on the CPU that hardware GPUs don’t.

If I have that correct…sounds neat. And explains relatively high cost in a 10Gbps hub for the hardware decompressor. You might get codec artifacts on the displays but I’d guess they’re minor unless you’re displaying demanding high-motion content.

I also didn’t realize the M1 Air was limited to 2 displays of which the internal counts as one, independent of physical port availability. Ya that’d be bad for a main PC.

Ya I would not recommend this setup for a main computer. I was planning on continuing to use my iMac as main computer and just using MacBook Air as secondary device (and indeed, that is what I was doing) but iMac has become pretty much unusable. M1 MacBook Air runs circles around it anyways. So this is very much a stopgap solution, not an ideal setup.

I agree!