iMac as a second monitor?

[DeltaMac]

You can't use an output coming from a VGA connection when using Target Display Mode (TDM) on your 27-inch iMac.
The main challenge is that VGA is an analog video signal, and DisplayPort is digital video.
Even if you had standard DVI port on your PC (DVI is a digital video signal), DVI is also not compatible with DisplayPort.

You'll discover that TDM requires either a thunderbolt, or Mini DisplayPort port.
http://support.apple.com/kb/HT3924
That's how it works when connecting Mac to Mac.
I don't know if it will possibly work on your PC - but the only way to find out is to install a graphics card that would give you a DisplayPort output. Some graphics cards could have a Mini DisplayPort, which is the ideal choice - but a DisplayPort to Mini DisplayPort adapter should be OK.
And, then I haven't heard of anyone trying that PC-to-Mac with Target Display Mode. It may not work, even with the correct video output on your PC.

 

[mcfly2]

And, then I haven't heard of anyone trying that PC-to-Mac with Target Display Mode. It may not work, even with the correct video output on your PC.

Read this thread, I use my iMac as an external monitor from my PC.

Hi there I've been trying to find out if i can use my imac (27" late 2011) as a external display for my PC-Gigabyte A75m-d2h motherboard- (that does not have thunderbolt port but has a VGA out).
================
My computer has a Mini DisplayPort and i purchased a Mini DisplayPort To VGA Adapter and i connected the vga cable to my the back of my PC. My imac interpreted the input from my pc as a external monitor. i can't find out how to switch that so my imac is a monitor.

THank you.

Read this thread. You can only use your thunderbolt imac as an external display from a thunderbolt output.

 

[DeltaMac]

@mcfly2
Thanks for pointing to your good posts in this thread. Good to get confirmation (and for me to remember to read the rest of the thread )
And, I also didn't recall that the poster had a thunderbolt iMac, but thought the 2010 was mDP. And, of course, that the poster needs TBolt out of the PC for that to work.

Curious - what graphics card do you have on your PC with Thunderbolt?
(nevermind, I still have to learn to read back a few posts - you don't need Thunderbolt, right?)

 

[mcfly2]

@mcfly2

And, I also didn't recall that the poster had a thunderbolt iMac, but thought the 2010 was mDP. And, of course, that the poster needs TBolt out of the PC for that to work.

He stated he had a late 2011 iMac, which would make it thunderbolt.

Curious - what graphics card do you have on your PC with Thunderbolt?
(nevermind, I still have to learn to read back a few posts - you don't need Thunderbolt, right?)

Right, I have a 2010 iMac. I go from displayport to minidisplayport.