Ok, this is probably a silly question but here goes: I just bought a new 6-core 2010 macpro with 5870 to replace the old 2006 quad core. I have 3 ACD displays, one 30" and two 23" on either side. Was using an ATI4870 to drive 30" and ATIXT2600 to drive the two 23". Planned to just put the 2600 in the new machine, and not worry about hassle of trying to get all three ports working on the 5870. Unfortunately the 2010 mac pro does not seem to recognize the older card properly. I also tried putting in the stock 2006 Nvidia 7300GT as well, but same issue. Only slot I tried was slot 3, which is where it was in my 2006 mac pro. Anyone else successively run older graphics card in new mac pro? I am wondering if it might be an EFI issue, although I thought these things were backwards compatible. Thanks!