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tpa77l3
(@tpa77l3)
New Member
Joined: 1 month ago
 
Hi guys,
 
I'm am trying to connect a PowerColor Mini Pro to three 4k monitors (LG 27UL850) via a MacBook Pro 16". I'm using the two display ports and a HDMI port on the back of the PowerColor Mini Pro to the USB-C ports on the back of the monitors using this and this cable.
 
I'm am not getting anything on the displays in this configuration. Any ideas why?
 

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itsage
(@itsage)
Illustrious Member Admin
Joined: 4 years ago
 

@tpa77l3, I would recommend using 2x DisplayPort to DisplayPort cables to power 2x of your LG 4K monitors from the PowerColor Mini Pro. Then HDMI to HDMI cable to the third one.

 

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tpa77l3
(@tpa77l3)
New Member
Joined: 1 month ago
 

@itsage, thanks for the reply. That's what I have ended up doing. I'm, just curious to know why the first cables didn't work.

 

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itsage
(@itsage)
Illustrious Member Admin
Joined: 4 years ago
 

@tpa77l3, Those cables don't always work bidirectionally because the monitors may or may not support that feature.

 

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2019 13" MacBook Pro [8th,4C,U] + RX 5600 XT @ 32Gbps-TB3 (VisionTek mini eGFX) + macOS 11 & Win10 2004 [build link]  


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joevt
(@joevt)
Noble Member
Joined: 3 years ago
 

Those cables don't always work bidirectionally because they are not bidirectional.

Some USB-C to DisplayPort cables are bidirectional (like the one from Moshi or Alogic). Bi-directional means you can also use it with DisplayPort output of GPU to USB-C input of display. The cable you linked did not mention bidirectional capability.

USB-C to HDMI cables can only work in one direction -> USB-C output from GPU to HDMI input of display. If you want to use HDMI output of GPU, then you need a HDMI to DisplayPort converter combined with a bidirectional USB-C to DisplayPort cable.

Not all displays with a USB-C port will work with a bi-directional cable that does not include a USB signal. Some displays with that problem may work with a subset of those cables (for example, the Alogic cable works with the 22 inch LG UltraFine 4K display but the Moshi does not).

https://egpu.io/forums/gpu-monitor-peripherals/does-a-usb-c-monitor-support-displayport-input-over-a-usb-c-to-displayport-cable/paged/4/#post-79127

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tpa77l3
(@tpa77l3)
New Member
Joined: 1 month ago
 

@joevt, Thanks. I've tried the Moshi cable without success. I have a look for the Alogic next.

 

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.

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