How to run a mid-2011 iMac with a mid-2013 gaming PC laptop in dual monitor mode?

Discussion in 'iMac' started by Matty Quinn, Feb 18, 2014.

  1. Matty Quinn macrumors newbie

    Feb 12, 2013
    New Jersey, USA
    A week or two ago, I posted to what I believe to be the same thread talking about how I had bought a MinIDisplayPort to VGA adapter and a fairly standard VGA cable (from RadioShack, not Apple) to try and run dual monitors on my iMac (All-in-one, circa mid-2011) and gaming PC laptop (circa mid-2012-13). Alas, it was to no avail. I got response on my last post, saying VGA is not the way to go. However, in that time, I found out that my iMac has a ThunderBolt port and not a MiniDisplayPort. I come here today to ask: Should I keep the VGA cable and get a VGA to ThunderBolt adapter, returning the MiniDisplayPort adapter? Should I buy a completely new adapter, e.g. VGA to Thunderbolt? Should I do something else it the entirety (namely?)? Thanks in advance.

    Best regards,
  2. xraydoc macrumors demi-god


    Oct 9, 2005
    You cannot do what you are hoping to do.

    One - It's an almost 100% certainty that your laptop's VGA port is output only. You cannot feed it an incoming signal and have it displayed on your laptop's display (presuming you're attempting to use your laptop as a display for your iMac; you post is not completely clear).

    Two - If you're trying to use the iMac as a display for the laptop, you'll also have to forget it. Your iMac has a Thunderbolt port, which means it'll accept video input from another TB-equipped Mac only.

    Three - Even if your iMac had a DisplayPort (mini-DP in the iMac's case) port and not a Thunderbolt port, it would only accept input from a DisplayPort source, not VGA, HDMI or DVI. Making the conversion from VGA or HDMI/DVI to mDP is possible, but it'll cost $100 (give or take a few bucks) for an active converter box.

    And just to clear up some technical factors, there is no such thing as a "Thunderbolt-to-VGA adapter" like you make mention of. The video signal of a Thunderbolt chain is DisplayPort. The DisplayPort monitor (or mDP-to-VGA adapter) has to be at the end of the TB chain - since there's no further daisy chain port on such devices. A Thunderbolt monitor can be in the middle of a chain, since it has an outbound TB daisy chain port, but obviously (or perhaps not so obviously) only works on a Thunderbolt-based Mac.

    In the computer world, do not assume adapters function symmetrically frontwards and backwards. Often (perhaps usually) they don't.

    Also, there is no such thing as a VGA-to-Thunderbolt adapter. You cannot take an analog video signal like VGA and convert it to a Thunderbolt/DisplayPort digital video stream with a simple, passive $25 adapter. Adapters with active conversion circuitry run around $100 if memory serves. This one ( will convert HDMI to mDP, but not VGA to mDP. Which, regardless, as I stated, won't work on your Thunderbolt-equipped iMac anyway.

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