ED#114 : Intel Turbo Boost Technology - Trapping The Unwary

For some users, the Intel Core i7 and Core i5 platforms offer a new level of performance, particularly for multi-threaded applications designed to make full use of its four processing cores. For reviewers like us, the upgrade is more than just about keeping up with the Joneses. The constant upgrading of our testbed is a necessity if we want to remain relevant to the community.

Needless to say, many reviewers and hardware enthusiasts have either migrated to the Intel Core i7 and Core i5 platforms, or are in the process of doing so. Unfortunately, this upgrade is not without its pitfalls for the unwary. When it comes to the Intel Core i7 and Core i5 processors, the biggest pitfall you have to watch out for is the Intel Turbo Boost Technology.

Most of us would have heard of this innocuous-sounding feature. Unfortunately, it is this passing familiarity that causes most of us to virtually forget all about it. Even as seasoned reviewers and hardware enthusiasts, we were once caught with our pants down and we have no doubt that many other reviewers and hardware enthusiasts too would have made similar mistakes. It is even possible that many are still unaware of the problems that Intel Turbo Mode can cause.

Problems? What Are You Talking About?

Intel introduced Turbo Boost as a quick way to improve the Core i7's single-threaded performance (and now, the Core i5's too) as many software are still single-threaded. Originally, Turbo Boost was designed to kick in when only 1-2 cores were active. However, Intel eventually enabled Turbo Boost even when all four cores were active. The Intel Turbo Boost was no longer about improving the Core i7 and Core i5 processors' single-threaded performance. It became an auto-overclocking feature.

As useful as Intel Turbo Boost is to the user, it is actually a bane to reviewers and hardware enthusiasts who need to accurately benchmark their systems. It can also cause trouble for overclockers but this is a topic best discussed elsewhere.

The problem with Turbo Boost is that it skews the benchmark results of Core i7 and Core i5 processors. With Turbo Boost enabled, Intel Core i7 and Core i5 processors will enjoy a significant boost in performance over all other processors. Our test results have shown that Turbo Boost generally improves performance by 3-4% but it can improve performance in some instances by as much as 7%.

This is an unfair advantage as the performance boost isn't due to improvements in the processor's design, but rather from overclocking it. Other competing processors (including Intel's Core 2 processors) would enjoy similar boosts in performance if they were similarly overclocked.

If you are a hardware enthusiast, you probably already know all this. However, are you also aware that Turbo Boost also skews test results between Core i7 and Core i5 processors? Some reviewers may assume that it would be okay to leave Turbo Boost enabled if they are only comparing Core i7 and Core i5 processors, or using testbeds based exclusively on those processors. After all, Turbo Boost is always enabled by default. Unfortunately, that would result in inaccurate results. Here's why...

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