Defining "throttling"

Before we get into what is throttling, we need to establish something: all Intel CPUs, desktop or laptop are designed to hit their full turbo boost clock once there is sufficient load on the processor (though in practice this is dependent on thermal limits). The actual turbo boost multiplier will usually vary depending on the nature of the load on the processor. For example, the i7-6700HQ has a base clock of 2.6GHz and a rated boost clock of 3.5GHz. But this 3.5GHz is only to be used when a single core is being stressed and is thus entirely useless under most forms of workloads. For two or three CPU cores being loaded, the turbo boost drops to 3.3GHz. For four cores being loaded, the turbo boost drops to 3.1GHz. Since a lot of games use four cores (and any DirectX 11 title on a Nvidia GPU forces CPU load to four cores with varying degrees of efficiency), this means your average turbo boost will be 3.1GHz in many sustained-load scenarios — though lighter tasks often make sure of the higher frequency of a single-core load. Unfortunately, a major problem is that the specifications and marketing for a laptop always advertise their Turbo Boost frequencies, even though they are not engineered to maintain (or sometimes hit) them in actuality.



I've established that a CPU should hold its turbo boost under load or it is considered throttling, but what is throttling, anyway? As you might have guessed, it is the intentional reduction of the speed of a processor due to some limiting factor in the system (generally power limit, current, or, most commonly, thermal). Note that when a CPU is at idle it will reduce its clockspeed, but the system — and myself — do not consider it throttling: while the clocks indeed drop at idle, the CPU does not return a throttling flag in this state (you can check using Intel's own XTU or one of many other CPU monitoring utilities). Generally, the throttling seen by sustained loads is thermal, but some laptops, such as Dell's XPS 15 9560 and its business workstation equivalent, the Precision 5520, are known to experience power limit throttling — likely as a result of insufficient cooling of their voltage regulator modules (VRMs).