How much power can the thunderbolt ports provide ?

[keblekek]

Hi all,

I just got my Mac Studio (with M1 Max inside), that I use in tandem with a MacBook when on my main desk, and I was wondering if it was possible to link them via usb-c/thunderbolt to provide both high speed network and power for the MacBook. So I tried, and it seems to work quite well, I can even see the total power draw going up a good 20w on the Studio when I plug the MacBook. The network connexion also works, but if I cut the wifi on the MacBook universal control stops working, so I have to keep both, which is a total shame on Apple, but anyway that's not my question. My question is : How much power can the Thunderbolts ports on the back provide to the MacBook (couldn't find that info on Apple's website), and if it falls under the 60w that the original brick provides, what would be the risks of using this config for a long time, if there are any ? Thanks.

 

[keblekek]

Well in case anyone else was interested, I think I answered my own question through experimentation. It seems it cannot provide more than the Thunderbolt standard dictates, which is 15w. At full power, the total power usage of the studio goes up about 18w, and the MacBook reports 13w coming in. Dunno if the difference is only due to efficiency or if somebody is lying somewhere, but clearly it seems close to 15. Anyway, I think the main downside of that setup is that if I do heavy stuff on the MacBook often, the battery will have to compensate for the power difference and it will age more quickly. Also it might totally deplete itself if I did a very big and long render/export kind of task. Probably not an issue for the Mac Studio though, it's the Max version so the PSU is way overkill and even on the Ultra there must be some power dedicated to Thunderbolt. It would be nice if Apple kept publishing this kind of info, from looking around it seems that they did in the past but they scraped it all from their website since then. Any thoughts ?

 

[VogonPoetry]

Hi. May I ask how you measured the power consumption of your Mac Studio / Thunderbolt ports? (Also, were any other of your four Thunderbolt ports in use when you were conducting the tests?)

I have two 4k monitors (one via HDMI and the other Display-port) and an external, bus-powered Thunderbolt 3 SSD connected to my Mac Studio. When I tried moving the HDMI monitor to a second Display-port connection, to free up the HDMI port, the SSD no longer powered up. If I connect the SSD when the system is running with the two Display-port monitors I get a notification stating "Accessory Needs More Power", "Disconnecting other accessories may allow this to work".
Trying various combinations suggests that the Mac limits the power initially(?) made available to each port based on the number of ports that are in use rather than the total power requirements of connected devices; connecting the SSD before one of the monitors and everything works, whereas connecting the second Display-port cable, even without a monitor on the end of it, before the SSD results in the Needs More Power notification.
It may well be that I have an overly power hungry SSD, but I'd love to be able to confirm that.
TIA.

 

[keblekek]

The Mac itself can report it through various means, what I personally use is this nice little utility : https://github.com/exelban/stats

Regarding your specific problem, I would say either one of your devices has a problem or Apple really ****ed up somewhere, it because it make no sense to me. A display port without anything attached to it should not draw any noticeable amount of power. I use every type-c port on the back of my studio, including one that charges my macbook, plus two HDDs on the type A ports, and everyone's seems happy with enough power to do its thing.

 

[VogonPoetry]

Thanks - that's very handy. I've been using the somewhat similar MenuMeters for years, but that doesn't report on power usage or break down the system temperatures.
When idle, with HDMI and Ethernet connected, Bluetooth and WiFi active, my Mac Studio consumes just under 8W. Each inactive DisplayPort cable adds another 0.4W and the Thunderbolt SSD enclosure with a 2TB NVMe drive briefly peaks at around 10W when first connected but quickly settles down to 5W, so I can't imagine it's a power supply issue and think it must have something to do with the BIOS or drive firmware. (If instead of one of the DisplayPort cables I connect a USB-C SSD to a Thunderbolt-capable port, drawing 2W, the Thunderbolt SSD can still be connected without complaint, so it's definitely the Thunderbolt / 2 x DisplayPort combination.)

There's another thread describing essentially the same issue so hopefully someone will get to the bottom of it: https://forums.macrumors.com/thread...ered-tb-devices-limited-title-edited.2340327/

 

[jwahaus]

I've been trying to determine what the maximum Amp power delivery for my Mac Mini M1's USB4/Thunderbolt ports. I haven't been able to find this documented online anywhere. I do know that system information reports 900mA maximum available for the USB3 SSD connect to a TB port. I tried powering a 16" portable 4K monitor from a TB port and although it worked it would only go up to about 1/2 brightness. I recently got a 16" portable QHD monitor and I am powering it from the TB port and it WILL go to full brightness and draws a maximum of 1.7A . The display doesn't show up in the system information report on either the USB or Thunderbolt tabs so there is no maximum power rating given by the OS.

It is really cool to be able to connect my display and power it from only a single USB Type C cable. I'm running my external SSD and monitor at the same time without issue.

Has anyone been able to find the written specification from Apple on how much current a TB/USB4 port can provide?

 

[jwahaus]

I should add that the 4K monitor drew 0.75A @ 20V (15 Watts) and the QHD monitor drew 1.7A @ 5V (8.5 Watts)

 

[pshufd]

Do you know how much power the front USB-C ports can provide? I currently use an Anker 5-port 60 Watt charger to power things but would like to be able to charge my mobile devices and accessories from just the Studio and the port hubs on my monitors. 12 watts would be ideal from the Studio.

I am also curious about the USB-C ports on the M1 Mac mini.

I put together a table of the power ouput of my monitors, mini and Studio and I may add a few other Macs to the list but it's of main interest to me so that I can get rid of USB chargers on my desk. I was rather surprised at the differing power outputs of the monitors.