File Compression7Zip is a free archiving tool and strong alternative to popular WinRAR. Integrated benchmark scripts are used in both 7Zip and WinRAR to test the performance of CPUs with multithreading enabled. One real life test with WinRAR is simulated while measuring the time needed to compress a ~1 GB folder with a few hundred smaller files. We can see that multithreading support does not work as well as it does in pure benchmark scripts.
WinRAR 3.9 Benchmark
WinRAR 3.9 compressingWhile both Core i3 and Core i5 661 processors do okay in synthetic archive benchmarks, in real life compression there is a issue with Intel's Speed Step and hence much weaker results than from the competition.
Older CPUs are benchmarked with Speed Step off for result consistency, but with newer Intel processors if you were to disable Speed Step on most models you automatically lose Turbo Boost features and with that a few percent in almost every application, so they are tested with Turbo Boost always set to On status.
What happens with WinRAR compression is that Intel's Turbo Boost fails to speed up the cores to the maximum value, and they get stuck somewhere between low idle and full load speed. Disabling Turbo Boost would improve WinRAR real-life compression performance but would also increase idle power consumption and decrease general performance in other applications.