I need help to resolve an issue with just one of my displays freezing / screen blacking out.

My set up:

  • iMac (Retina 5K, 27-inch, Late 2015)
  • Processor: 3.3 GHz Quad-Core Intel Core i5
  • Memory: 8 GB 1867 MHz DDR3
  • Graphics: AMD Radeon R9 M395 2 GB

Displays 4 (three external):

  • iMac 27"
  • HP 2010 20" Display, 1600x900 x 2 with only DVI-D and VGA inputs
  • Samsung S27R35x 27" Display, 1920x1080, HDMI and VGA inputs only

I am connecting the two HP 20" (old) displays via a DVI connection through Thunderbolt Adapters, using up both available Thunderbolt ports, then using a DisplayLink Adapter to connect the 3rd 27" Monitor via HDMI to USB (this is the monitor freezing / blacking out).

So, my question is, am I better trying to get a better cabling, if so what? Thunderbolt Adapter? Or is a graphics card needed?

Note: monitoring the AMD Radeon R9 GPU history, nothing is spiking out of control and my RAM steadily at 7GB from a 8GB available.

Any recommendations greatly appreciated.

  • More than likely, it’s the DisplayLink adapter (low quality). Technically, you need another graphics adapter (card) and that’s what that adapter is doing. Thing is, instead of your GPU handling things, you’re now using CPU cycles. Personally, I would look at getting a Thunderbolt Dock with multiple display ports so you can hook up 2 displays there and free up your other TB port for a DVI or HDMI adapter for the third monitor.
    – Allan
    May 29, 2020 at 17:19
  • Thanks @Allan! I have a StarTech Thunderbolt dock, but this does not seem to support three external displays. I have 27" direct into HDMI, DVI to TB, and then the TB -> TB into iMac with a spare DVI adapter into the remaining TB port into the Mac. Any configuration doesnt support the third display. May 29, 2020 at 18:00
  • 1
    @MattD.Webb I have the same problem apple.stackexchange.com/questions/414368/… Have you find a way to make it possible with 3 external monitors?
    – Miao
    Feb 24, 2021 at 13:36


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