Hi there, I had a decent mac for vidoe editing which was stolen,I did not have the bucks to buy a decent replacement and think I nought a bit of a dud when it comes to editing! I ugraded RAM to maximim allowed (12G)use Premiere Pro, and with the i7-4510u Processor, dual-core but soldered so I have learnt. My edits lag,even with 1080p footage, and 4K out of the question except when editing in proxy mode or 1/4 resolution. Is there any way of ugrading the card, even externally, or does that affect BIOS too etc? Best,Dennis