I'm thinking about purchasing a USB-C hub with dual HDMI/DP out. If M1 Mac Mini supports it, I feel the MBA should too. Can't imagine Apple adding a dedicated HDMI chip in the Mac Mini.
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What are the chances of M1 MBA supporting dual-displays with a hub?
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That's exactly what Apple's done on the Mini. Actually, they've done this for years.
AFAIK, the Mini supports one display on the HDMI port on the back of the machine, and one display via USB-C/Thunderbolt. The laptops are supporting one display hardwired internally (to the LCD panel), and one display via USB-C/Thunderbolt.
Ah, that makes a lot of sense. I never accounted for the internal display.
I always thought the Thunderbolt spec capable of daisy-chaining displays, maybe that's not quite accurate though.
The M1 is a bit anemic when it comes to the number of DisplayPort streams the GPU provides. The A12X/A12Z also supports 2 DisplayPort streams, so it doesn’t seem like they’ve changed a whole lot there except for adding the TB controller to feed the second DisplayPort stream into, instead of a USB-C controller.
While Thunderbolt allows 2 DisplayPort streams per bus, it’s not mandated. And Apple is really the only one that uses two streams on a single port (LG 5K requires this to work, XDR can use this for machines that don’t support display stream compression). If my memory isn’t wrong, I believe pretty much all other cases of driving two monitors from a single Thunderbolt port relies on DisplayPort MST to work. Something Apple hasn’t supported on the Mac well, if at all.
You likely know more about such matters than do I, but I'll add this tidbit for whatever it's worth.
I dock my MBP15 in clamshell mode using a single TB3 cable to my Caldigit TS3+ -- to which I have two monitors attached. One via displayport and the other via the TB3 downstream port, I think with a USBC to Displayport cable. I'm away from home this week so can't check.
I am hopeful the M1 MBA / MBP will support dual monitors in clamshell mode this way. If not, my MBA order will be cancelled.
Yeah, things get a little messy in terms of support here. I could also be mis-remembering how dual DisplayPort streams over Thunderbolt works. It seems like if the device can provide 2 streams to a single bus, TB3 will allow both to be sent across a single port. I really need to spend time reading up more on the spec at some point.
It’s not impossible, but I’d consider it unlikely. The ability to re-route the second stream when the lid is closed seems like something Apple would call out. Also, since the Mini doesn’t allow two displays over TB3 either, it doesn’t seem to me like the ability to re-route the stream is implemented on the M1.
Indeed, the unknown is whether the display stream is able to be rerouted in clamshell mode.
I'm not sure the Mini's inability is directly applicable though since it has the dedicated HDMI port - not sure there's a means to disable that output.
All speculation of course. Time will tell. My order won't ship for a couple weeks, and even if it does we're in the holiday extended return period so there's nothing to be lost in trying it out.
It'd be really nice if it works though.
No, The M1 Macs use DisplayPort 1.4 HBR2 with DSC to communicate with the 6K XDR.
If they didn't have DSC, then they would need to use dual HBR3 over Thunderbolt to get 6K, which means it would be able to connect two displays to the Thunderbolt ports (either a single port or one per port) but Apple does not mention a dual display ability for Thunderbolt so we can assume that DSC is being used instead of dual HBR3 for 6K.
It is mandated for Thunderbolt 4. Since there's only one DisplayPort connection to the Thunderbolt controller in the M1, Apple cannot call it Thunderbolt 4. This is the first time Apple has made a Thunderbolt host with only one DisplayPort connection.
Yes, many PC's have a Thunderbolt controller with only one DisplayPort connection. There are some with two DisplayPort connections. The GC-TITAN RIDGE, GC-ALPINE RIDGE and some other similar Thunderbolt 3 add-in card have two inputs. I think there's a motherboard with built-in Thunderbolt controller having two inputs.
Thunderbolt is capable. All the Thunderbolt controllers that Intel builds for use in a computer host context have two inputs for Di splayPort streams. But if the system vendor only connects one of those two inputs then you'll only get one stream out on the ports. Thunderbolt has to be hooked to the GPU to get output.
M1 uses Apple's homegrown TB controller ( or perhaps licenses from ASMedia , but I doubt they'd admit that if true). If Apple stripped down their TB controller to save space ( quite likely) they only have one input internally.
That actually aligns very well with the M1 likely having high overlap with "A14X" ( a SoC for the iPad Pro). They build a GPU that only drive the embedded screen and do one external one.
Apple also built the new GPU in the context of Display 1.3/1.4 which can support very high resolutions ( 8K ) with just one stream. Previously needed two v1.2 streams to drive 5K (and up). So looking forward at future displays they could handle large displays with just one external stream. So that is all they did.
Well, they did any one "extra" small resolution stream for the Touch Bar. But that isn't routed externally on any of the systems.
There is a possibility if they built multistream support into the feed directly from the GPU.
Put the TB port into pure Alt-DP mode and do a direct feed from the GPU which does the DP standard of dual streams.
I suspect Apple didn't implement that part of the DP standard. As it would probably grow the GPU's output handling section incrementally. If they did implement it, then it seems doubtful that they would hide it in the Tech Specs. [ not impossible as Apple probably isn't doing much certification with DP chaining monitors but perhaps some design snuck it in there as a flourish and a more complete implementation of the DP standard. ] Apple's "Tech Specs" are sometimes just limited to point to other Apple Store stuff to buy.
Plus it would need driver support. DP multiple stream is typically used by Apple jus to drive larger resolution of the same screen, not different ones.
If the older Ultrafine 5K displays are only "supported" in 4K resolution mode then even the MST to drive high res is kneecapped here. ( they are on the current iPad Pro. Wouldn't be surprising if that didn't change on the next one. )
FYI - I reached out to CalDigit since I own a TS3+ dock and here's their response.
In my question I referenced clamshell mode, so I am interpreting the response in that context:
Now I need to decide if that's truly make-or-break for me. I've been using my desktop setup with just the one 27" QHD display for a few months now having repurposed my 2nd display (1080p) to my wife's home office setup and haven't had much incentive to buy a new display so maybe not.
In my question I referenced clamshell mode, so I am interpreting the response in that context:
Now I need to decide if that's truly make-or-break for me. I've been using my desktop setup with just the one 27" QHD display for a few months now having repurposed my 2nd display (1080p) to my wife's home office setup and haven't had much incentive to buy a new display so maybe not.
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Only hope for multiple displays now is eGPU but people have already said the M1 won't support eGPU. Which AMD kexts have both ARM and x86 code in Big Sur? Use the file command on each binary to find out.
find /System/Library/Extensions -path '*/Contents/MacOS/*' -type f -exec file {} \; | grep AMDOr Apple may provide that support in the future mid/upper-tier four-port systems not yet transitioned from Intel to ARM, with this limitation of the two-port systems being a differentiator.
Folks need to remember - M1 isn't "it" - there's more to come, this is just the lower-tier two port systems. Notice the Mini and MBP lines still have mid/upper-tier four port Intel options you can buy. They're by no means done.
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find /System/Library/Extensions -path '*/Contents/MacOS/*' -type f -exec file {} \; | grep AMD | grep arm64eResult is empty - no AMD drivers have arm64e.
Most everything else has arm64e (USB, FireWire, Serial, AHCI, SCSI, etc. )
As I posted in another thread - M1 appears to only support one single display via the Thunderbolt 3 ports. Not one display per port - one display total between the two TB3 ports. TB3 dock or not, adapter or not, daisy chaining or not. Only one single display output over both TB3 ports.
It appears from the tech specs of the MBA and MBP that only one single external display is supported - period. If you want two displays, you have to use the built-in display as one of them.
And if you want an M1 Mac running two external displays, it has to be a Mini, and it has to connect to one of them via HDMI port.
It appears from the tech specs of the MBA and MBP that only one single external display is supported - period. If you want two displays, you have to use the built-in display as one of them.
And if you want an M1 Mac running two external displays, it has to be a Mini, and it has to connect to one of them via HDMI port.
By looking at ioreg from a M1 Mac, it seems DSC is supported for the XDR. To be sure, we need someone to test a SSD (~400 MB/s).