I have a Mid 2012 11" MacBook Air and I'd like to drive 2 external monitors. This question has been asked before, and the solutions so far are:

  1. Use a Thunderbolt to DisplayPort adapter and a USB DisplayPort adapter. This is what I'm using now and the USB DisplayPort adapter provides poor framerates, graphics glitches, and application incompatibilities.
  2. Use a Thunderbolt dock which splits a single monitor signal apart into two monitors. This doesn't work well if you want to take advantage of macOS multi-monitor support since the OS is fooled into thinking there's only a single monitor.
  3. Use two Thunderbolt monitors. Apple is discontinuing its Thunderbolt monitor. It seems that Dell has already discontinued theirs. This is also a very expensive option (roughly $2000) if you already have two DisplayPort screens.
  4. Get a Thunderbolt to PCIe enclosure along with a PCIe graphics card. This is a very expensive option.
  5. Daisy chain two DisplayPort 1.2 monitors. This doesn't work on the 2012 MacBook Air because its Intel HD 4000 graphics core only supports DisplayPort 1.1a.

Technically, it seems like it should be possible to drive two DisplayPort monitors from a 2012 MacBook air:

  1. The processor uses Intel HD 4000 graphics which supports 3 displays (so long as two of them are DisplayPort and driven by the same PLL).
  2. The PCH (SLJ8B Mobile Intel® QS77 Express Chipset) can support multiple DisplayPorts.
  3. The Thunderbolt controller (Intel DSL3510L Cactus Ridge 4C) also supports two DisplayPort monitors.

Is there a technical reason (for instance, the PCH is configured to disable a DisplayPort) one cannot drive two DisplayPort monitors from a 2012 MacBook Air? I'm looking for a way to demultiplex the two DisplayPort signals off the single Thunderbolt connector.

  • Huh? I think you've answered your own question. There is only one Thunderbolt/mini-DisplayPort port, so you can only plug one monitor into it, so you need a USB-DisplayPort adapter. You were explaining that the adapter was giving you crappy quality, but why are you blaming that on the iGPU's inability to drive two external monitors? Have you tried only using a single external screen with the USB adapter. If you have problems with that, the problem is with the adapter, not the computer – NoahL Mar 3 '17 at 2:12
  • The quality problem is with the adapter--"the USB DisplayPort adapter provides poor framerates..." So I'm looking for a way to use two external screens without the USB adapter. The graphics card in the Mac supports three screens. You stated, "There is only one Thunderbolt/mini-DisplayPort port, so you can only plug one monitor into it." That's not entirely correct--see item 3 in my question. I'll modify my question at the end though, since it's not clear what I'm asking for. – watkipet Mar 7 '17 at 15:57
  • Not sure if it matters however, which Mid 2012 MacBook Air do you have, the 11" or 13"? It is always good to be explicit and specific with the hardware info in cases such as this regardless. – user3439894 Mar 7 '17 at 16:12
  • I added the MacBook dimensions (11"). I hope it doesn't matter, but I got the information on the Thunderbolt controller (DSL3510L) from a teardown of the 13" model, not the 11" model. – watkipet Mar 7 '17 at 16:50
  • What I mean by "there is only one TB/mDP port" is that you can't plug two monitors into the same port and see different screens on each (without a Thunderbolt hub). – NoahL Mar 7 '17 at 18:10

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