Earlier quoted context omitted.
Which cpu model do you have in the MacPro5,1?
Intel(R) Xeon(R) CPU E5620 @ 2.40GHz quad core, dual cpu. so 8 cores total. multi-core performance is great! we use it as a Unity build box and it functions great since we're normally doing multiple builds at a time, and image compression & shader compilation are multi-threaded. but it's definitely slower if you are just doing 1 build at a time. sucks that in 2 years when Apple starts requiring the latest Xcode for i…
There's a very noticeable performance improvement from (eg) the E5645's, let alone the E5620's.
Saying that as I used to use a self build box (Supermicro motherboard) with dual E5645's as my desktop, but it always "felt" a bit slow. :/
Had the opportunity to upgrade to X5675's, and now it "feels" fine interactively due to the higher base and boost clock.
The highest model, X5690's, from all reports are literally no faster in use than the X5675's (maybe thermal throttling?). So not worth the extra spend. ;)