IDF wrap-up: Nehalem Turbo Boost

Will it help or hinder overclocking Intel’s new chip? Tim Dean reports from the recent Intel Developers' Forum.

Remember back in the 1980s when David Hasselhoff was cool, and his car, KITT (Knight Industries Two Thousand) was even cooler? Remember whenever he was being chased by the bad guys, and he needed that extra bit of oomph, he’d reach down and hit the Turbo Boost button, and bam, he’d be hurtling through the air while something typically exploded nearby?

Well, now you can have a similarly hyperbolic experience with your new PC, at least when Intel’s new Nehalem processor architecture hits the streets in the Core i7, planned for November this year. One of the key features, according to Stephen Powlowski, who gave an extensive tech presentation at the recent Intel Developer's Forum in Taipei, on the Nehalem, is a re-emphasis on single core performance. That might sound a bit odd when talking about a processor that should ship with two, four or eight cores. But according to Powlowski, 'customers' have been 'demanding' better single threaded performance – which probably means Intel has been paying attention to the fact that the vast majority of single threaded software used on desktop PCs still gets nary a boost from multi-core processors.

So, Intel has come up with this nifty Turbo Boost trick. Here’s how it works. Say you have a quad core processor, and you’re running software that is utilising each core. Awesome, all four cores do their thing and the processor runs at its base frequency and voltage level. But say you are running only two threads simultaneously. In this case the processor will shut down two entire cores, lock stock and L2 cache. But it doesn’t just stop there, it takes part of the power saved from the two inactive cores and redirects them to the active cores, boosting their voltage and frequency. Even better: run a single threaded app, like most games, and it will pump all available mojo into just the one core.

All this is enabled by two main features: the first is called Power Gate, and represents Intel’s latest efforts to prevent leakage across transistor gates, particularly when they’re powered down; and the second is a brand new chunk of transistors integrated into the core in a block called the Power Control Unit (which I find uncannily reminiscent of the Master Control Program in Tron, just to keep with the 1980s theme...).

These voltage and frequency boosts are relatively minor, however, with it only pushing things up one or two 'steps' at a time. So we’re talking hundreds of megahertz here, not a 50 percent boost or anything.

Also, all these Turbo Boost shenanigans are handled purely in firmware, so we have no control over the process, besides being able to switch it off entirely. The unanswered question is how Turbo Boost will affect overclocking. Intel has recently been expressing some sympathy for overclockers – at least in its own straight-laced, bow tie and nicely parted hair kinda way – even to the extent of releasing its own tool, but when Powlowski was asked about whether we might one day have any access to the Turbo Boost settings, he was particularly noncommittal. Guess we’ll just have to wait, overclock, and see.