Turbo Boost on Gigabyte Mainboards
Theory is great, because it is all so logical and clear and we can take all the time we need trying to put together an optimal solution. After that it is time for a practical experiment and we end up choosing not what looks best from the theoretical standpoint, but what works best in real life. It turned out that disabling Turbo Boost on Gigabyte GA-EX58-UD5 and GA-EX58-Extreme mainboards is not the best thing to do. There are several reasons for that, and primarily it is the fact that on these mainboards Turbo Boost works not the way it is supposed to, according to the theory we have just discussed above. For example, I have never seen a CPU clock frequency multiplier being increased two steps up at a time, from 20x to 22x, even if there was a single-thread application running. No, one time during the memory tests Everest did report a 22x clock multiplier. However, since I couldn’t reproduce it again, I consider it to be a program glitch.
Moreover, I am almost 100% certain that mainboards increase the clock multiplier to 21x for all working processor cores, and not only in case one or two cores are utilized. I determined the core frequency by performance readings. Namely, I measured the speed with enabled Turbo Boost and multiplier increased to 21x, and then disabled it and increased the base clock speed far enough to obtain the same resulting CPU frequency with a 20x multiplier. I got almost the same performance, which couldn’t have happened if there had been only core working with a 21x multiplier with enabled Turbo Boost. Of course, the memory frequency in this case was different, so to be 100% certain one needs to use an Extreme Edition CPU with an unlocked multiplier.
In our Intel Core i7-920 Overclocking Guide we mentioned that ASUS P6T Deluxe mainboard allows “disabling the processor’s ability to control its power-related parameters without deactivating Turbo Boost. This trick makes it possible to statically increase the processor clock multiplier by 1 over the nominal independent of the workload and its current level of power consumption”. We got the impression that Gigabyte mainboards disable this control automatically once you enable Turbo Boost. CPUID Hardware Monitor utility that we often use to monitor temperatures and voltages proves this point. There is an additional “Powers” parameter there for Intel Core i7 processors and its maximum is always at 130W with disabled Turbo Boost.
The utility doesn’t measure the actual power consumption. The maximum value will remain unchanged even if we increase the CPU Vcore, which is impossible. However, once we enabled Turbo Boost, this value jumps to 150W:
Well, if the clock frequency multiplier increases by 1 for all cores simultaneously, it makes overclocking on Gigabyte mainboards a lot easier. First, with a higher multiplier, you don’t need to push the base frequency that far up in order to obtain the same processor frequency. It automatically means that the rest of the frequencies connected to the base one will not go too high either. Moreover, even if the one of the processor cores frequency will go two steps up at once during single-thread load, we shouldn’t be concerned about losing stability. Unfortunately, this implementation of the Turbo Boost technology ruins all its advantages. Our processor can no longer turn into a high-frequency single- or dual-core CPU: it will always remain a common multi-core processor. What a pity…
The next reason why you shouldn’t disable Turbo Boost mode on Gigabyte mainboards is because they will not set the correct processor voltage in this case. The nominal voltage of our Core i7-920 processor is by no means just idle talk. I assumed that it was 1.225V, but Gigabyte mainboards often showed 1.21875V. The difference is not dramatic in this case, but very often they read 1.18, 1.16 or even 1.13V. I thought that the boards detected the current processor core voltage during system boot-up, so I disabled processor power-saving technologies. However, the voltage readings still remained lowered.
However, it didn’t cause us any trouble. Once Windows booted the core voltage increased to 1.2V under maximum CPU load. It can be considered normal taking into account possible voltage drop during maximum CPU utilization and some monitoring errors. However, it only was like that with enabled Turbo Boost. Once we disabled it, the CPU Vcore read only 1.1V. Our preliminary tests showed that this low voltage was nevertheless sufficient for the CPU to work fine at nominal speeds. However, it was definitely not enough for any overclocking. And even if we manually increased the CPU core voltage preventing the mainboards from lowering it, we could always get better overclocking results with enabled Turbo Boost.