Besides the performance tests in multi-threaded applications, we also wanted to find out how the background processes will affect the performance of our systems in a resource-hungry primary application. To check this out we used a popular single-threaded SuperPi benchmark to measure the time it takes out testing participants to calculate 2M digits of the Pi while there are a few copies of multi-threaded WinRAR utility running in the background.
The obtained results turned out very interesting. It appeared that with the increase of background workload Intel eight-core system could yield to AMD Quad FX with only two dual-core processors onboard. The reasons for that lie in the efficiency of work with memory subsystem, because in SMP systems it also serves to exchange data between the processor L2 caches. AMD Quad FX platform that uses fast quad-channel unbuffered DDR2 SDRAM boasts higher data transfer rate than the i5000X or Nvidia nForce 680i SLI based systems. Therefore, as the number of executed tasks increases, the platform built with Intel processors starts falling behind the AMD Quad FX at some point. Of course, intensive work with the memory subsystem as well as the need to transfer data between different CPU cores acts as catalyst to this situation.