How to make sure windows 8 uses all computing power for only 1 process?

Question

If I render an image in windows 8 commandline for example with blender/cycles my machine sometimes has a low cpu usage. The render task starts with 100% cpu usage, fall down after 2-4 hours to 25%, stays there for 3-6 hours and sometimes it raises up to 100% again. It cant be a blender issue, because when I render the same in windows 7 it works as expected.

Any Ideas on this?

Answer 1

1. First you should try to set the priority and affinity of the process in the Task Manager just to give it a little bump up in comparison to other USER programs (note the user part as this doesn't affect much the SYSTEM processes, the efficiency of this is debated as the priority queue used by Windows depends on many things, so as you said this works as expected in Windows 7 so maybe its some background process particular of Windows 8 that is stalling the process)

2. I have heard many users complaining of idle/background maintenance in Windows 8 and 8.1, you should try to deactivate this and try again, ill leave a link to a tutorial on deactivating the background maintenance that sometimes may be bothersome to other programs executing as well Background Maintenance

   Here you can find the superuser question: Disable "automatic maintenance" in Windows 8