Intel’s upcoming Core i7 processors will feature a turbo mode, as announced on Day 1 of IDF. Although not quite like the retro turbo mode button found on computers of the late 1980’s, the turbo mode on Core i7 will still result in increased single threaded performance. The technology is based on the idea of dynamically increasing the frequency of the CPU when not all the cores are in use, archiving higher single threaded performance when that is all that is required.
The technology is aided by the improved power management features found on Nehalem also announced at IDF. The Integrated Power Gate technology will shut off idle cores, reducing their voltage to zero, rather than just lowering the power provided to them. Not having as many cores on using power and producing heat, will allow other cores to use more power, increasing the performance of those cores, while still not exceeding the maximum TDP of the processor.
In the following scenario for example, if you are using a Core i7 with 4 cores, and the game you are using uses only a single core, the other three cores will turn off, reducing the heat produced by your processor, allowing the only running core to be automatically overclocked for higher performance. This new technology may be a compelling reason for many to no longer choose the faster clocked dual core processor over the slower quad core, as the quad core could offer now equal single threaded performance at the same price.
Exactly what type of improvement is expected form this turbo mode is yet to be seen, but early leaked demonstrations show at least a single stepping of improvement, 22 to 23 for example. What this Turbo Mode means for overclockers is also yet to be seen also. Some are saying overclocking on Nehalem will be very difficult if Intel so chooses to make it so however. Leaked information also indicates that production CPUs will self overclock by up to two speed bins — for example jumping from 3 GHz to 3.2 GHz or even 3.4 GHz.
With this kind of headroom, it will be interesting to see how far enthusiasts will be able to push Core i7 processors. Even Intel indicated to us in June that Core i7 silicon is extremely healthy. Our own tests revealed that Core i7 processors will have considerable amount of headroom in terms of clock speeds.
For those who remember, the original "turbo button" found on many PCs back in the day, was there not actually to speed up the CPU, but actually to slow it down. When activated, the CPU actually ran at full speed. With the turbo button switched off, the CPU would be underclocked to allow certain legacy applications to run at "normal" speeds instead of "too fast."