Desiring some information/speculation on why Apple did what they did with Mac Pro in 2012. In early 2011 they retooled the MacBook Pro line to include thunderbolt and again in 2012 to include USB 3. They completely refreshed the form factor for the retina models later that same year... So...with Thunderbolt already around for more than a year, why didn't they press a new logic board into service in 2012? PCIe3.0, SATA III, and thunderbolt were all readily available in 2012 (and somewhat in 2010). I can understand not including Thunderbolt, since expansion is available internally. But how hard would it have really been to machine a new LB? Is it because 6,1 was likely already well into development and changing the configuration of 5,1 would have perhaps been detrimental to parts inventory/future sales?