Hyper-Threading: best thing since sliced thread?

When Intel starts adding the initials 'HT' to its Pentium 4 stickers, you know that Hyper-Threading is going to be a mainstream buzzword in no time, writes Ben Hardwidge.

Hyper-Threading has been doing the rounds for a few months already, but was previously an exclusive possession of Xeon servers and workstations. We first saw it in the 2GHz Xeon-based Armari RX860HT, but you can now buy it in a mainstream PC from Evesham or Dell.

In basic terms, Hyper-Threading takes the CPU's unused resources and applies them to other threads where possible. It works with Windows XP, which detects the HT chip as two processors (also it works with Linux -ed). This theoretically makes it faster in multithreaded apps, but could also speed up multitasking between apps that use different parts of the processor.

Does it make a difference? In terms of single, application-based 2D performance, no. In fact, with Hyper-Threading enabled, we saw a slight drop in performance when testing the Evesham, with its benchmark score dropping from 1.74 to 1.66. However, while some tests such as CorelDRAW were noticeably slower with Hyper-Threading, some were still slightly quicker. Our Cleaner video-encoding and Excel Business tests (the latter runs at the same time as a movie in Media Player), for example, were slightly quicker.

More importantly, the multitasking tests should show an improvement in the quality of movie playback, even with intensive benchmarks running in the background. However, we noticed no difference in either of our Excel benchmarks with Hyper-Threading on or off.

The real test for Hyper-Threading, however, was how well it would cope with a multithreaded application. To put this to the test, we ran a benchmark in LightWave 7, which renders a frame from Lost in Space.

With two threads selected, the frame was rendered in 13 minutes, two seconds with Hyper-Threading disabled, and 11 minutes, seven seconds with it enabled. What's more, with Hyper-Threading disabled and rendering on a single thread, it took 11 minutes, 49 seconds.

So Hyper-Threading does improve some areas of multitasking and can also speed up dual-processing tasks. Due to the way Windows prioritises the CPU's workload, it isn't going to speed up everything, as our 2D benchmarks have shown. However, it can be turned on and off in the BIOS on most motherboards, so you can enable it according to your priorities.

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