Is Hyper-Threading worth it?

Although Hyper-Threading has been available in various Intel CPUs since the Xeon MP in 2002, Intel deems it so important that it's Hyper-Threading support (and not trivialities such as socket type or memory support) that delineates between Core i5 and Core i7 processors.

We therefore wanted to investigate whether the status that Intel gives Hyper-Threading is really merited. In short, Hyper-Threading tricks the operating system into thinking there are twice as many processing cores in the system as are actually present. This is possible, since even when a processor core is at 100 per cent load, there will be some resources (such as the FPU units) that aren't used. The ability to send two execution threads through a single processor core is intended to accelerate multi-threaded applications and multi-tasking.

To put Hyper-Threading to the test, we benchmarked the Core i7-860 with it enabled and disabled in the BIOS. The tests were run with Turbo Boost (rev 2) disabled in the BIOS so that the CPU was running at the same constant frequency during the tests.










As usual with Hyper-Threading, highly multi-threaded yet relatively simple tasks that such as video encoding and ray tracing reacted well. The video encoding test of our Media Benchmarks ran eight per cent faster with Hyper-Threading on, and Cinebench completed 13 per cent quicker.

However, the image editing and multi-tasking tests and games all ran slightly slower with Hyper-Threading enabled. Unfortunately, this is something we've come to expect. Despite several tweaks over the years, if either execution thread requires access to the same resource unit of the CPU's execution core at the same time, the second execution thread must queue until the unit is free. This 'thread stalling' explains why more complicated tasks might run slower with Hyper-Threading enabled.

With that said, we found that the slowdown due to Hyper-Threading was less than five per cent, and as Hyper-Threading doesn't increase the power consumption of your PC, enabling Hyper-Threading is worthwhile. Unless we really needed the extra multi-threaded performance, we wouldn't go out of our way to have Hyper-Threading, though, so we're mystified as to why Intel felt it necessary to differentiate its Core i5 and Core i7 ranges on this feature alone.