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For all that own or know this in the new version.

Is the Thunderbolt output compatible with the Mini DisplayPort to VGA Adapter?

  • If not, how do we connect our external monitor?
  • If yes, with the 27" version there are two ports, can we connect 2 external monitors?

BTW: I'm asking about standard monitors, not the Apple Cinema Display.

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up vote 4 down vote accepted

Thunderbolt is a superset of Displayport Apple page on Thunderbolt says

And because Thunderbolt is based on DisplayPort technology, the video standard for high-resolution displays, any Mini DisplayPort display plugs right into the Thunderbolt port. To connect a DisplayPort, DVI, HDMI, or VGA display, just use an existing adapter.

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with 2 ports ... should I be able to add 2 extra screens? – balexandre May 19 '11 at 11:36
The Apple docs seem to imply that – Mark May 19 '11 at 11:44

Simply plug in one DisplayPort/Thunderbolt display or video adapter per port. That gets you two screens in addition to the iMac screen.

There is a little confusion over multiple displays on one thunderbolt chain and real experience is limited since no thunderbolt monitors are shipping widely as of mid-August 2011.

If you care about the details or difference between thunderbolt or displayport, How the devices chain is a little different.

In this configuration (video out, one display per port) all Mac accessories that physically fit will work. I haven't heard of any third party devices that break when used with Thunderbolt instead of DisplayPort.

The only limitations where an older DisplayPort-only device will fail to work with Thunderbolt is the video-in mirroring feature. It looks like someone that has a new Thunderbolt MacBook Pro can send the video from the portable to display instead of the iMac (the iMac becomes a monitor with the Mac running behind the scenes - not displaying on the iMac). It looks like an older DisplayPort portable such as an Air or older DisplayPort out Macs won't be able to send video to the new Thunderbolt iMacs like they could to the older DisplayPort iMacs.

I personally hope a firmware update on either or both ends might make this work later, but today, this is simply wishful thinking.

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It's one Thunderbolt chain per port, so there could be multiple monitors, but only one DisplayPort device per chain. – CajunLuke Aug 23 '11 at 18:59

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