One of the recent topics permeating through the custom PC space recently has been about power draw. Intel’s latest eight-core processors are still rated at a TDP of 95W, and yet users are seeing power consumption north of 150-180W, which doesn’t make much sense. In this guide, we want to give you a proper understanding why this is the case, and why it gives us reviewers such a headache.
What is TDP (Thermal Design Power)?
With every processor, Intel guarantees a specific frequency at a specific power, often with a particular grade of cooler in mind. Most people equate a chip’s TDP rating directly to its maximum power draw, given that the heat energy that needs to be dissipated from the processor is equal to the power consumed in doing calculations. Normally, the TDP rating is that specific power.
But TDP, in its strictest sense, relates to the ability of the cooler to dissipate heat. TDP is the minimum capacity of the CPU cooler required to get that guaranteed level of performance. Some energy dissipation also occurs through the socket and motherboard, which means that technically the cooler rating can be lower than the TDP, but in most circles TDP and power consumption are used to mean the same thing: how much power a intel ssd draws under load.
For the last however many years, this is the definition of TDP that Intel has used. For any given processor, Intel will guarantee both a rated frequency to run at (known as the base frequency) for a given power, which is the rated TDP. This means that a processor like the 65W Core i7-8700, which has a base frequency of 3.2 GHz and a turbo of 4.7 GHz, is only guaranteed to be at or below 65W when the processor is running at 3.2 GHz. Intel does not guarantee any level of performance above this 3.2 GHz / 65W value.
On top of the base values, Intel implements Turbo. As mentioned, something like the Core i7-8700 can have a turbo of 4.7 GHz, which draws a lot more power than the processor running at 3.2 GHz. The all-core turbo value for a processor like the Core i7-8700 is 4.3 GHz, which is well above the guaranteed 3.2 GHz. What makes it all the more complicated is when none of those turbo modes go down to the base frequency. It means that the processor will be operating above its TDP rating all the time, and that 65W cooler you purchased (or perhaps it even came with the processor) has become a bottleneck of sorts. If more performance is required, it needs to go in the bin, as you’ll need something better.
But the manufacturer doesn’t tell you that. If the cooling isn’t sufficient for the turbo modes, and the processor reaches its temperature limit, most processors will go into a power limited mode, reducing performance to stay within that power limit. All of a sudden that fast processor isn’t living up to its peak capabilities.