Hats off to Dr_Haribo!!  I had a 5770 in my Mac 2,1 going steady at 150Mh/s (I know about 2 yrs too late) I just recently added another 5770 w an external PSU (not really needed but have a 5970 on the way) I'm using 10.7.4 and w x2 5770 only getting 160-170 Mh/s.  I've been changing things up a bit to see if its my hardware configuration-- 5770 w stock PSU in slot 1 and 2nd 5770 in slot 4 ext. PSU for some breathing room.  I'm going to try beta version again, last week it wasn't too stable, but I was hoping in theory to get like 250-300 Mh/s so I'm kinda bummed.  I guess w osX there isn't much in the way of GPU manipulation w catalyst (tried AMD's site for downloads) my next step is to boot camp Linux or Win7 but really don't want to, and to switch to pci slots 1 and 3.  Now the MacPro 2,1 is pci-e 1.0 :-/ but everything I had read w Mac n 5770 had it at 150 Mh/s.  any suggestions w this would be appreciated.  I really do enjoy using BitMinter and will probably stick w it if/when my BFL ASIC arrives (maybe by June/July). Cheers and thanks!!