MBP - TB3. Normal Behaviour?

[Lee_Mac]

I currently have a LG 34WK95U with a 16” MBP connected via a Caldigit TS3 Plus via TB3 with a couple of Drobo‘s with the monitor being the last in the chain, the MBP’s lid is shut. Also directly connected is a Mac Mini via HDMI and a Corsair One via the display port.
My currently problem I’m trying to get it the bottom of is. If at any point I switch monitor input to either HDMi or Display port, the MBP shuts down. Stupidly annoying if I’m wishing to do work on either of the other two computers.

Is this normal TB3 behaviour?

 

[raknor]

I currently have a LG 34WK95U with a 16” MBP connected via a Caldigit TS3 Plus via TB3 with a couple of Drobo‘s with the monitor being the last in the chain, the MBP’s lid is shut. Also directly connected is a Mac Mini via HDMI and a Corsair One via the display port.
My currently problem I’m trying to get it the bottom of is. If at any point I switch monitor input to either HDMi or Display port, the MBP shuts down. Stupidly annoying if I’m wishing to do work on either of the other two computers.

Is this normal TB3 behaviour?

It is not TB3 behavior but how clamshell mode works on MacBooks. By switching the monitor's input, it disconnected the display connection over TB3 to the dock and switched to HDMI. The MacBook noticed the display was unplugged and went to sleep because the lid is closed.

Switching monitor's input actually counts as the display removed event because the display internally switches a Mux and physically disconnects the LCD and connects it to the other input selected. This causes a signal called the Hot Plug Detect to be dropped on the thunderbolt/displayport interface which tells the GPU on the mac that the display went away even though the cable is plugged in.

 

[Lee_Mac]

Ah ok got ya, regardless of the ‘prevent sleeping if monitor is off’ is checked. Which works fine typically, can be a bit of a chew waking it up sometimes but I believe that’s a LG issue.

So the only practical why around it is to have the lid open?

 

[raknor]

Ah ok got ya, regardless of the ‘prevent sleeping if monitor is off’ is checked. Which works fine typically, can be a bit of a chew waking it up sometimes but I believe that’s a LG issue.

So the only practical why around it is to have the lid open?

The checkbox only applies to the internal display when the lid is open. Only way around is to have the lid open.

 

[Lee_Mac]

I think I'll have a swap about with which computer is using which cable. Thanks for the replies

 

[Lee_Mac]

Found a simple fix. Just turn the 'turn the display off' option to never. Stops it sleeping regardless