Quote Originally Posted by powellandy View Post
Possible bug reports

- How is OCCT 3b12 supposed to behave on clean vista x64 sp1 install. Says dx9 not installed and no GPU tests - is this normal - should I install dx9?

- How is linpack OCCT 3b12 supposed to behave on Hyperthreading Intel P4 630 (Prescott). System info says 1 core and running linpack test shows 100% CPU usage in OCCT but only 50% in Process Explorer. Using CPU OCCT test with hyperthreading box ticked gives 100% usage in both. Should linpack stress both 'cores'?

Andy
Those are not issues, but they need explanations

* You have to update DirectX9 even on vista (it is DirectX10, but it does have everything for DirectX9 too). That's why OCCT is complaining

* That's hyperthreading I'll try to keep the explanation short & understandable. Hyperthreading causes your OS to see twice the real amount of real cores on your system (for instance, if you've got 2 cores, Windows will see 4). However, you can view those 4 cores as "2 are real, 2 are "benefits only" from HT". So if you load the 2 real cores, and the 2 others are IDLE, you'll see, In the task manager, 50% workload. In reality, you'll have both of your physical cores loaded, and no benefit from HT taken. Those 50% means "95% of the real horse power of your CPU", to keep it short.

OCCT CPU test has 2 different behaviours :
* Without HT as DC, it will launch one test per physical core (i.e. "real" core). Thus you'll see 50% load, even if 95 or so% of your CPU is busy.
* With HT as DC checked (by default, as it proved more efficient on HT CPUs), OCCT will launch one test per core, physical or logical (i.e. real and "fake" cores). You'll see 100% workload in the task manager.

The linpack test has only one mode : 1 test per real core. Thus the 50% in the task manager.

The hard part is understanding that only half of your cores in the task manager are "real", and that the others represent the benefits from HT.