i Have the 2011 Thunderbolt iMac, im building a gaming PC with this Motherboard
http://www.scan.co.uk/products/asus...-s-sata-raid-pcie-30-(x16)-hdmi-mini-displayp
which has 2xThunderbolt and expressly has video out for the Haswell GPU, ill test it on the iMac and let people know if it works once its built (the primary monitor is going to be a Nvidia 3D approved one for gaming, but i don't see harm in trying out thunderbolt for the forum once the rig is built)
i may even try the lucid MVP software or whatever it is that allows the discreet graphics to be passed through the on chip GPU if its available for this board and GPU combo
I have a similar motherboard as you, asus p8z87-Expert (
http://www.asus.com/Motherboards/Z87EXPERT/ ). it has one thunderbolt.
I tried different ways to use imac(2011 with thunderbolt) as the extender monitor in windows 8 with p8z87-expert, but all failed. however it's ok to connect a regular dell monitor though thunderbolt->dvi method.
The PC does find new hardware(you can hear the warning sound) when connet/diconnect imac though thunderbolt, but the PC just dosnt recognize imac as a monitor.
And i did some research about the lucid MVP software, seems unless asus integrated the software solution into the bios, there is noway to output the video though the thunderbolt to iMAC.
(lucid MVP does supported some earily asus motherboard, check the list here:
http://www.lucidlogix.com/mvp-product-list.shtml. However, the current motherboard Z87 not on the list yet.)
There must be a driver missing that make PC not recognize iMAC as a monitor, And the missing driver can be found in the lucid MVP solution.
So, only if someone can figure out how the lucid MVP software output the video data, the way to drive the iMAC as a monitor, otherwise, what we can do is sit and wait Apple to release the driver for windows, which is seems hopelessssss....