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Old 2004-01-30, 18:13   #2
nomadicus's Avatar
Jan 2003
North Carolina

F616 Posts

Originally Posted by Unregistered
And something weird is when I open Windows Task Manager while running Prime95 it says only 50% CPU usage..
You have hyper threading (HT) turned on. This means that Windows sees two virtual CPUs when in reality it is just one physical CPU. The task manager displays it as 50% of the combined two virtual CPUs which really means 100% of the physical CPU (hey, it's confusing, but that's virtual for ya).
If you have Windows XP, you can leave HT on but for each % on the second virtual processor means that prime95 runs that much slower (the reported 20-30% boost with hyper threading enabled does not apply to prime95 due to its optimized assembly code).
Personally, I have Windows XP and I have HT turned off so the stats make more sense to me (just my preference).
Windows NT is reported to have an inefficient scheduler which means you should have HT turned off to maintain best performance if you are running NT.
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