No, MC using not alot CPU. All Menu Items of all Programs slow down. It need then longer time to show anything from all manu bars and all programs.
And a indicator of the insufficiency are the time which MC need fopr loading a Tab-Layout. After restart it load the tab layouts very fast, almost so fast like in my Virtual-Box Windows XP. (In the Virtual-Box Windows XP the tabs are extremely fast loaded, and there is no problem with slowing down this)
When MC need much time for loading tabs without any reason (no CPU-Usage) then are also the menu bars of all programs slower. And this is also the same problem when only one instance running, but not so extremely hard, when only one instance running is the slow down of other programs just a little bit, not easy to detect. Yesterday i tested running only one instance and detected problems. Today i have decided to run only one instance without starting any other Commander like FC. I will write my results of today testing tomorrow. The problem is only after some work.
Maybe the Graphics Driver cause the problem. This i think because in the Virtual Machine (Windows XP) it run better.
I use a AMD Fusion A6-6310 with Win8.1 64 Bit and Microsoft Office 2016 64 bit. Other installed Programs are for example BC, TC, FC2009, FCXE64.