The graph below shows the results for Cinebench R15, single threaded and multi-threaded. As we expected the largest performance jumps occur on the tocks, specifically Sandy Bridge and Haswell. The biggest performance gain was primarily the introduction of Sandy Bridge, and the smallest jump is found on the introduction of the Ivy Bridge chips. The differences between Ivy and Sandy Bridge were quite small so this can be explained, however the jump on introduction of the Broadwell is like-for-like less than 4%.
In the Tech Arp x264 benchmark the largest gains again are on the two tocks, Sandy Bridge and Haswell. It is peculiar that in this benchmark Ivy Bridge also performs a lot better than its predecessor. The performance gains on Broadwell are limited compared to the Haswell processors.
We admit that with only two benchmarks it is impossible to draw final conclusions, but in these two benchmarks we do not see the promised 5% performance increase that Broadwell should have compared to the Haswell processors. For large performance gains we have to wait until the next tock, the new architecture.
Fortunately we do not have to wait long until the new tock arrives, the first Intel Skylake processors are not far away from introduction, and when they arrive we will obvioulsy conduct this test on the new architecture.