Intel Westmere 32nm Launch & Clarkdale Core i5-661 CPU Review

Feature Test: Intel Turbo Boost

For those of you who skipped the microarchitecture section, let's recap what Turbo Boost is.

Turbo Mode is an feature that automatically unlocks additional speed bins (multipliers) and allows the processor to self-overclock based on thermal conditions and workload. For example, if the Power Control Unit (PCU) senses that one core is active and the other is in an idle state, it will use the unused power and thermal headroom to overclock that single active core to ensure superior single-threaded performance. Conversely, if you are running a multi-threaded application, the PCU will measure the thermal headroom and if the processor is running cool enough it will overclock both cores. On the Core i5-600 series chips, Turbo Mode can provide a 266Mhz speed boost in single or dual-threaded workloads and 133Mhz in triple or quad-threaded applications.

Although the results will be fairly self-evident, let's check out the performance gains that Turbo Mode provides on our Core i5-661 model. As per the above, thermal conditions permitting, it will run at 3.59GHz for single or dual-threaded workloads and 3.46Ghz triple or quad-threaded applications.

	Intel Core i5-661 Turbo Boost Off	Intel Core i5-661 Turbo Boost On	Performance Difference
Cinebench R10 64-bit: Single Thread	4384	4666	+6%
Cinebench R10 64-bit: Multi-Thread	10505	11061	+5%
HDxPRT	183	190	+4%
Lame Front-End	160 secs.	146 secs.	+9.5%
Photoshop CS4 64-bit	224.5 secs.	212.2 secs.	+6%
SuperPi 32M	738.582 secs.	702.639 secs.	+5%
WinRAR 3.8.0 Compression	260 secs.	255 secs.	+2%
x264 HD Benchmark	13.82 FPS	14.25 FPS	+3%
3DMark Vantage: CPU Score	9631	10136	+5%
Valve Particle Simulation Benchmark	103 Score	107 Score	+4%

As you can see, there are some marginal performance improvements in multi-threaded applications, and some more noticeable speeds boosts in single-threaded applications like Lame Front-End and SuperPI. Some people consider the Turbo Mode feature a mere gimmick, and perhaps it is for enthusiast users who overclock, but who can criticize a free and automatic 133-266Mhz speed boost?

Now when you combine Turbo Boost with Hyper-Threading, you have two technologies that can work together to create some very noticeable performance improvements. Will this allow a dual-core processor to compete with native quad-core models? Let's find out with some real benchmarks.