Comment by AceJohnny2 | Hacker News Reader

Comment by AceJohnny2 | Hacker News Reader

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FWIW, I am currently using a CalDigit TS3+ with a (Intel) MBP, with dual displays (one over DP, one over USB-C (DP)). They work as separate displays, not mirrored.

I also tested an HP G2 Dock [1], because its dual-DP ports gave me more options, only to find that macOS can only use those two ports as Mirrored to each other.

Apparently [2], this is because the HP G2 implements its two DP ports as DP1.4 MST (Multi-Stream) on a single link, and in that mode macOS will only support a Mirrored configuration. It cannot (as of Big Sur 11.1) use them as separate displays.

I'm told you can also use the HP G2 with separate displays by plugging one monitor into one of its USB-C outputs, kind of like how I'm using the CalDigit TS3. I tried the one labeled USB-C (DP), and that stayed mirrored, but apparently I should've tried the Thunderbolt downstream port instead. I returned the dock before I knew or could try this.

All this to say, I'm disappointed by the mess of an ecosystem that Apple has built around Thunderbolt 3. But I can't say I'm surprised.

[1] https://store.hp.com/us/en/pdp/hp-thunderbolt-dock-120w-g2

[2] https://medium.com/@sebvance/everything-you-need-to-know-abo...

Intel's TB3 controllers can't do both TB3 daisy-chain and provide two DisplayPort endpoints. That's why most TB3 docks that have two DisplayPort ports don't have a second TB3 port, and why the HP had to use MST to have both. It's also why 5k+ displays may or may not support being daisy chaining, depending on whether it's using two DisplayPort links.

MST isn't necessarily great because over an HBR2 link it doesn't have the bandwidth for dual 4k60, and there's still a lot of stuff that doesn't support HBR3 links. And MST + hotplug is still a mess. So you're just trading for a different set of confusion.

Well the fact that Apple doesn't want to support MST on macOS doesn't help either. Funny enough, installing Windows on the same Mac makes MST work just fine.

Their push has always been towards Thunderbolt. I was disappointed in this decision, but not really shocked.

Apple advertised MST support for Sierra or High Sierra and never delivered. Like you mentioned, daisy chaining does work on the same hardware in Linux and Windows.

I'm happy with the CalDigit TS3+. I just got one and it's able to drive two external 4K 60Hz displays (one usb-c, one displayport) from both my Intel MBP or from my Dell XPS 17, hot swappable. In the latter case, that's over three 4K displays including the laptop. (I didn't realize the XPS actually had >4K resolution until opening the display settings tool).

I just started with this configuration two days ago, so we'll see. It's not completely glitch-free yet: I noticed the mouse (also plugged into the TS3+) glitched a bit yesterday, and once one of the monitors couldn't be detected from the XPS once and required reboot. XPS also shows a low-power charger warning in tray when plugged into it, which I wish I could disable but oh well. Still, it's worked way better than I'd expected so far with no hassle. Completely replaces my desktop setup and hot-swaps are generally seamless.

I haven't noticed any major CPU or power spikes. Fan isn't doing anything weird. But I'll look out for it.

just in case, OWC Thunderbolt 3 to Dual DP [1] adapter work fine with two 4k@60Hz separate displays (with MBP15 2019). And seems similar Thunderbolt3 -> Dual DP adapters also should works well. But I agree that is a big mess with that stuff, I brought lot of usb-c->hdmi adapters before found solution with works fine with 2 displays (some of those adapters only supports 30Hz, some can slow-down MBP performance dramatically with 2 displays).

[1] https://www.amazon.com/OWC-Thunderbolt-3-Dual-DisplayPort-Ad...

The M1-based macs support USB4, which is conceptually an upgrade over TB3 (supporting multiplexed streams of PCIe, DP, and USB). However Apple conspicuously does not prominently advertise that support, which I'm guessing is due to a lack of ecosystem.

USB4 is prominently displayed on the Marketing and tech-spec pages for the M1 Macs:

https://www.apple.com/macbook-pro-13/specs/

https://www.apple.com/macbook-pro-13/

I would have expected to be able to daisy chain 2 dell monitors (wqhd, nothing 4k fancy), but I was unable to. Also, finding a dock with reliable 2 monitor output has not been easy, and at the end I pluged both monitors to the laptop and call it a day. That the laptop has to power up the discrete graphics for running external displays and goes crazy with the fans while you are just browsing is something that exasperates me, but not being a really fan of apple, I'm not blind and see that what they have accomplished with the M1 is an exceptional product, and sooner or later I will ditch my 16 inch for one of those. The only thing is that almost nobody will want to buy an intel macbook and those aren't going to maintain their value like before.

I’d like to add to this my disappointment in using a G2 dock. Have had two different HP G2 docks (using DP and USB C) for dual external displays and they both broken over two years of sitting on my desk. I don’t know what’s happening to them but eventually both external displays start flashing and getting artifacts and USB and Ethernet devices start randomly disconnecting.

Just my experience. Hope other haven’t had those issues.

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