Hello all. I'm new to the forums. I've been a Mac user since I purchased my first G4 Laptop in 2005. I currently share a 2009 Mac Book and have a (increasingly long in the tooth) G5 dual core 2.0Ghz Power Mac all to myself. Details of my question are below, but if you'd prefer to skip that my question comes down to this: Are there differences between the 2009 Mac Pro 4,1 A1289 and the 2010/2012 Mac Pro 5,1 1289 once the firmware has been flashed? If so what are they? Please forgive me if this has been dealt with before, but my searches of past forum posts did not turn up the information I was looking for. I intend on purchasing a used Mac Pro either a 2009 4,1 MB535LL/A; a 2010 5,1 MC561LL/A; or a 2012 5,1 MD771LL/A (those are are 8 or 12 core models). From what I gather the differences between the 2010 MC561LL/A & 2012 MD771LL/A are minimal and the upgrade options for both are identical. If there are any differences in upgrade options please let me know However, I cannot find any indication that there are differences between the 2009 4,1 MB535LL/A and the 2010-2012 models once the firmware has been flashed. Unfortunately I cannot find any explicit statements that there are not differences in the upgradability of the two models once the firmware is upgraded. Are there differences between the 2009 Mac Pro 4,1 A1289 and the 2010/2012 Mac Pro 5,1 1289 once the firmware has been flashed? If so what are they?