Can u point me to a reference on what supplies work and how to do? Thanks
Also assume same arrangement would work for 4870 for OSX and 295 for Bootcamp?
nanofrog's suggestion is very useful. I have a completely external cheap ATX supply from my local PC store. It says HiPoint on the box and I asked for the cheapest thing that has 2 6-pin connectors. I run it with the pins shorted as per nanofrog's link.
With an eye on the future and possibly trying a 295, I have just got a ToughPower 1000W supply with several 6- and 8-pin connectors. This is totally over the top for a single card, but will run a 295 and if I build a hackintosh later it will power several cards.
The main thing, if you want a 295, is to get a supply with one of the newer 8-pin supplies. AFAIK, all the other GTX 200 series need at most 2 6-pin.
The 4870 is an official Apple Mac Pro design so should use up at most two (i.e. all) of the built in connectors - your external PSU will take care of the 295.