It's a 10 cores (with HT => 20 logicals) Broadwell with a little overclocking (3GHZ -> 3,8GHz, and DDR4 higher, 3200 (or 2300... 2400), don't remember precisely, i'm in break at work).
I'm not using placebo, but a 3 pass encode (i'm targetting VBR not CRF) with high enough settings.
First pass is around 0.7fps to 1.0fps.
Second pass is around 0.5fps.
Third pass is around 0.6fps to 0.7fps.
Each pass has increased quality parameters, but last pass uses data informations from previous pass, wich increase the speed (otherwised it would be 0.5fps or even a little less).
When targetting Blu-Ray or HW Player devices with 1080p x264 i'm using placebo (+ Blu-Ray specific or DVXA specific), also 3 passes, it takes less than a day in this case. I start the evening, the tomorrow evening when back from work, it's finished.
But 4k with x265... Another speed, and with "less quality" than my x264 settings, because with my x264 settings on x265 4k, i'm around 0.05fps - 0.1fps.
Even if i'm a "quality crazy", one month for a movie begin to be a little excessive...
So for 4k/x265 i had to reduce my quality level.