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User profile for user: afx22
afx22 Author
User level: Level 1
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Mac Mini 2014 - Dual Monitor Issues

Hi, I have a late 2014 Mac Mini and two almost new Iiyama monitors.  The monitors work perfectly with my work laptop (a pc running windows).


But I'm really struggling get the Mac Mini to drive both monitors.


I have 2 x mini display port to HDMI cables.  (These are made by Rankie - whoever they are).  I also have a HDMI to HDMI cable.


I'd assume that I can just use mini display port to HDMI cables to drive both monitors via the Thunderbolt ports, from a cold boot up.  But that doesn't work.


I can get one monitor working at a time but the other monitor will show no signal detected.  Sometimes the apple logo appears and then the one screen goes blank and I get 'no signal detected'.  This is true with either cable and either monitor, so I assume the cables are fine.


I've tried booting up with one monitor, then plugging in the other and trying to 'Detect Display' in the settings and this doesn't work.  Nothing is detected.


I have had some success by booting with a single monitor using the HDMI to HDMI cable, then plugging in the other monitor using the mini display port to HDMI cable, then trying 'Detect Display'.  This sometimes works but certainly not always.  And then when the Mac Mini or Monitor goes to sleep, only the single HDMI to HDMI monitor wakes back up.  Occasionally the second monitor does wake up but displays a 'scrambled' image.


Can anyone please help?  Shouldn't it just work via both Thunderbolt Ports?


Thanks in advance.

Mac mini, macOS 10.15

Posted on Apr 22, 2020 1:13 AM

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User profile for user: den.thed
den.thed
User level: Level 9
77,602 points

Posted on Apr 22, 2020 10:13 AM

I don't have a 2014 Mac Mini to test. The support article only refers to using Mini DisplayPort to HDMI, DVI, VGA Adapters and not Mini DisplayPort to HDMI cables. see > https://support.apple.com/kb/SP710?locale=en_US

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User profile for user: danielleary
danielleary
User level: Level 1
118 points

Apr 23, 2020 3:27 AM in response to afx22

It could be a cable issue.

Officially the 2014 Mac mini supports the two following configurations for dual monitors

  • Use of 1 HDMI port and 1 Thunderbolt/MiniDP port (can be suing a thunderbolt to HDMI conversion, usually in the form of a dock, or a simple DisplayPort to HDMI conversion, in the form of a single cable or adapter with normal HDMI cable)
  • Use of 2 Thunderbolt/MiniDP port (again, same as above in thunderbolt or mini Display Port usage, can be mixed)
  • Unofficially they also support dual monitors out of one thunderbolt port with the use of a Thunderbolt 2 dock that has 2 independent display controllers attached to the Thunderbolt bus. I used to use my Mac mini 2012 in this configuration. (don't expect a high refresh rate with this method)

So it sounds like you should be fine there, and you are correct, use of both thunderbolt ports should absolutely work. Which is why I suspect it could be a cable issue or possibly a monitor issue with correctly identifying itself to the computer when it wakes back up, sometimes using TVs as monitors cause this issue. A TV monitor sometimes won't wake up in time to let the Mac know it's an available display to use when the Mac is woken up and so the Mac thinks the monitor was unplugged while it was asleep so it will continue normal operation as if that display was not there.


Would you mind sharing what monitors you are using?

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User profile for user: afx22
afx22 Author
User level: Level 1
10 points

Apr 24, 2020 2:15 AM in response to danielleary

Thanks for your help. Monitors are both IIyama PL2730H.


Btw. It’s been working fine for the last two days. I’ve no idea what is different. That’s using one via Thunderbolt to HDMI and the other as HDMI. I’ve labelled which cable goes to which monitor, so I can recreate the physical setup, in case I run into issues in future.

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Mac Mini 2014 - Dual Monitor Issues

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