How can all cores on a hyperthreaded CPU go to 100%

[curiousmike]

Hi, you know when you goto Task Manager, it shows you by default all cores (ie physical & hyperthreaded) on the system? Given the way hyperthreading works is by having a second set of registers for the CPU (ie instruction and data for thread 1 is on registers 1, and instruction and data for thread 2 is on registers 2), and when say thread 1 requires the CPU to access slow I/O such as memory or disk, the same physical CPU can temporary switch to run thread 2 using the instruction and data on registers 2.

So if my CPU has 4 physical cores, and I see on Task Manager, 8 cores (physical + hyperthreaded), I should never see any of these 8 cores going 100% but rather the sum of both physical + hyperthreaded core going 100%.

Anyone knows why we can see on Task Manager 100% CPU usage for any of the cores (physical + hyperthreaded)?

 

[rvcjew]

Off wikipedia: With HTT, one physical core appears as two processors to the operating system, which can use each core to schedule two processes at once. In addition, two or more processes can use the same resources: if resources for one process are not available, then another process can continue if its resources are available. Hyper-threading - Wikipedia, the free encyclopedia

So if they are all at 100% that means your program is using all of the cores and it is working properly depending on the type of program (3d rendering for example will saturate your cores.) if your PC is doing nothing and has all cores at 100% then you have another issue.