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How do i use my 'old' 2012 iMac as a secondary screen with my 2019 new iMac?

Can I use my existing late 2012 21" iMac (macOS Catalina installed) as a secondary screen for my brand-new 2019 iMac 21" with macOS Catalina?

Meaning iMac as extended screen for another iMac?

(I have seen no posts until now on this subject)



iMac Line (2012 and Later)

Posted on May 4, 2020 2:28 AM

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Question marked as Top-ranking reply

Posted on May 4, 2020 5:27 AM

maybe too many converters


if it was me then I would convert usb-c(thunderbolt3) to minidisplayport connector (thunderbolt2)

https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter?fnode=d292eb649561977b2cba3b95c71360358ff792cad4838486cf37d1dda34fa77b5075aa0683ae868ddd6272405b0f35479dc52690281a56008eef3280dd24edba08957cebdfefce351f43a4a1ac070ed8e429e990fcdaeccc98251db9c314a516da3ceb5d04e2090769049699e6f4a1b1&fs=f%3Dadapter%26fh%3D4595%252B45b0


both thunderbolt3 and thunderbolt2 use displayport signals to convert displayport to hdmi and then back to displayport seems like an unnessesary source of issues.


more about displayport and thunderbolt

https://www.journaldulapin.com/2012/12/12/thunderbolt-and-mini-displayport-differences-and-compatibility/

9 replies
Question marked as Top-ranking reply

May 4, 2020 5:27 AM in response to MUMA-ANTWERP

maybe too many converters


if it was me then I would convert usb-c(thunderbolt3) to minidisplayport connector (thunderbolt2)

https://www.apple.com/shop/product/MMEL2AM/A/thunderbolt-3-usb-c-to-thunderbolt-2-adapter?fnode=d292eb649561977b2cba3b95c71360358ff792cad4838486cf37d1dda34fa77b5075aa0683ae868ddd6272405b0f35479dc52690281a56008eef3280dd24edba08957cebdfefce351f43a4a1ac070ed8e429e990fcdaeccc98251db9c314a516da3ceb5d04e2090769049699e6f4a1b1&fs=f%3Dadapter%26fh%3D4595%252B45b0


both thunderbolt3 and thunderbolt2 use displayport signals to convert displayport to hdmi and then back to displayport seems like an unnessesary source of issues.


more about displayport and thunderbolt

https://www.journaldulapin.com/2012/12/12/thunderbolt-and-mini-displayport-differences-and-compatibility/

May 4, 2020 9:01 AM in response to MUMA-ANTWERP

Use your iMac as a display with target display mode - Apple Support

You need a Thunderbolt 3 adapter

Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter - Apple

and a Thunderbolt cable.

https://www.apple.com/shop/product/MD861LL/A/apple-thunderbolt-cable-20-m

It will not work with Mini DisplayPort, even though the connectors will fit. Do not use any non-Thunderbolt cables or adapters, such as HDMI.


If the 2012 iMac is running Mojave or Catalina, you will have to erase it and install High Sierra.

May 4, 2020 5:22 AM in response to Rudegar

This is not working for this particular iMac-iMac constellation, hence my question.

I have on the one side Thunderbolt 3 bus (USB-C connector) Firmware version 1.34.0 40 Gb/s on my 2019 iMac and Thunderbolt 2 bus (Mini Display Port Connector (type 2?))Firmware 0.12.3 10 Gb/s on my 2012 iMac.


A local @reseller sold me the following kit ;-)

1x USB-C to HDMI (Sitecom) +1x HDMI-HDMI (Belkin high speed) + 1x HDMI-Mini Display Port (hama)


After connection nothing happened.

What went wrong?



How do i use my 'old' 2012 iMac as a secondary screen with my 2019 new iMac?

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