If you want to stress test your multi processor CPU, then FFT or Fast Fourier Transforms is quite an useful tool. This freeware tool inspired from CPU-Z and other CPU test tool, shows detailed information about physical and logical processors in the system. It also includes a CPU Benchmark feature for speed testing. It can automatically utilize and tests all CPU cores and show an errors found during the test. The interface is neatly arranged into tabs, first one shows processor information.
The second tab has the testing options and the results along with the errors.
The stress tests puts load on the CPU and hence it is better than you do not run any other applications in the background. It checks for any errors and notifies you in case any encountered. You can finally benchmark the results and optionally publish it online with the processor details.