Multiple TBolt-3 Docks Connected w/Power?

jasonmvp

macrumors newbie
Original poster
Jun 15, 2015
19
4
Northern VA
Hey folks -

I've been running into a random (ie non-reproducible at will) problem with my new 2018 MBP. I have two CalDigit Thunderbolt-3 docks on my desk, because I'm powering 3 4K displays with the laptop. One dock is connected to each side of the laptop; they're not sharing the same side. So they're both getting the full 40Gbits/sec bandwidth.

The problem I'm running into is that the Mac will randomly freeze, crash, and reboot when I connect both docks up. It's a bit odd and I wish I could put my finger on WHY it's happening.

The thing I'm starting to wonder is: is the laptop getting confused by having 2 85W power supplies connected to it and barfing on that, perhaps? Is anyone else using multiple TBolt-3 docks on their MBP; ones that provide power? Any issues?

Thanks.
 

chrfr

macrumors G3
Jul 11, 2009
8,304
2,594
Hey folks -

I've been running into a random (ie non-reproducible at will) problem with my new 2018 MBP. I have two CalDigit Thunderbolt-3 docks on my desk, because I'm powering 3 4K displays with the laptop. One dock is connected to each side of the laptop; they're not sharing the same side. So they're both getting the full 40Gbits/sec bandwidth.

The problem I'm running into is that the Mac will randomly freeze, crash, and reboot when I connect both docks up. It's a bit odd and I wish I could put my finger on WHY it's happening.

The thing I'm starting to wonder is: is the laptop getting confused by having 2 85W power supplies connected to it and barfing on that, perhaps? Is anyone else using multiple TBolt-3 docks on their MBP; ones that provide power? Any issues?

Thanks.
Can you connect the 3rd display directly to the Mac without a dock in there?
 

jasonmvp

macrumors newbie
Original poster
Jun 15, 2015
19
4
Northern VA
Oh, hmm. I think I'd talk to Caldigit directly on this one. Their products are generally pretty solid.
I have. They said "We dunno." Their support is a bit on the less-than-useful side, from my limited experience.

At this point I'm just trying to see if anyone else is loony(?) enough to have 2 x 85W power supplies connected to a MBP.
 

killawat

macrumors 65816
Sep 11, 2014
1,446
2,191
The issue is not about having two power supplies. The system will only allow one and ignore the other.

However with dual 4K you are on the upper bounds of of saturating your TB3 pipe meaning your other devices are starved. depending on what you have connected to your dock, your displays and peripherals could become disconnected, leading to a crash.

In this case I’d recommend an eGPu such as the sonnet and Radeon ex 580 combination. Yes it sucks that you are unable to use the docks for their primary purpose of connecting displays, but you need more horsepower for triple 4K.
 

jasonmvp

macrumors newbie
Original poster
Jun 15, 2015
19
4
Northern VA
The issue is not about having two power supplies. The system will only allow one and ignore the other.
OK, good to know.

However with dual 4K you are on the upper bounds of of saturating your TB3 pipe meaning your other devices are starved.
Not even remotely true. Math is fun; let's do it.

TBolt-3 == 40Gbps

2 x 4K/60 @ 32-bit color == 32Gbps

This leaves me wiggle room of about 8Gbps, give or take. And the dock in question only has a keyboard, mouse, and a 5Gbps Logitech CamLink attached to it.

In other words: nothing's being starved.