[Shiunbird]

You inspired me to do some testing.
I couldn't get GPU in Cycles enabled in macos, but it works fine in Windows.

I got a cMP with dual x5675 (2x 6 cores @ 3.06) and a Vega 64.
The 3.3 Blender splash screen demo scene renders in 27 minutes on the CPUs and 7 minutes on the Vega 64 under the newest Blender in Windows 10.

edit: enabling both CPUs and GPUs raises the time to 11 minutes.