Finally got around to upgrading the CPU in my Mac Pro which I bought new in 2009. It was a low end system with one CPU @ 2.66 GHz. I just installed a W3690 CPU (after the firmware update to 5,1) and I have a couple of questions. First, the System Overview is reporting that I have 32GB of 1333 MHz ram, when I really have 32GB of 1066MHz ram, is this normal? Second, can I go to 48 GB of ram with this CPU (3x16GB sticks)? Third, I am running the El Capitan OS, if I want to move to Sierra OS, is this a simple download from the Apple store and the upgrade "just works" on this 2009 firmware-upgraded box? Thanks! UPDATE: Actually, my system is smarter than me... I just took a look at the installed memory and even though I ordered 1066 MHz ram, I was sent 1333 MHZ. So, that's nice and you can ignore my first question!