I keep reading that it is not possible to use the new 5K iMac as an external display for any of 's current hardware line-up, due to inadequate graphics power (what about Mac Pro?) and possibly a need to update DisplayPort version. Firstly would these be required hardware upgrades or would they be possible in software upgrades? Secondly, the iMac has it's own onboard graphics processing hardware. Would it be possible to update Yosemite to allow for some (or all?) of the graphics resource requirements to be offloaded to the iMac...? Thirdly, ...or indeed a new Thunderbolt Display. Same case, same panel, presumably there would be room to keep some onboard GPU hardware within this product to work in the same way?