I can run four independent processes (i.e. not using multiprocessing, with no links at all between them) yet the results show that only one core is running. Where is this lock taking place? Why would a tkinter process need to know about another tkinter process?
	
A little bit of history I have learned is that prior to Windows 7, the GDI sub-system imposed a global lock system-wide so that only one process (one thread) could write to the display at one time. This meant in effect it was a one-core GUI desktop. From Windows 7, this was supposed to have been 'fixed', but all I have read is that the "GDI lock became more fine-grained, reducing concurrency bottlenecks". I wonder did anyone ever measure performance in real-world scenarios to demonstrate whether there was in fact any improvement?