Intel Core i7-10700 vs Core i7-10700K Review: Is 65W Comet Lake an Option?

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Over the years, Intel’s consumer processor lineup has featured its usual array of overclocking ‘K’ models, and more recently the ‘F’ series that come without integrated graphics. The bulk of the lineup however are still the versions without a suffix, the ‘nones’, like the Core i7-10700 in this review. These processors sit in the middle of the road, almost always having a 65 W TDP compared to the 91-125 W overclockable models, but also having integrated graphics, unlike the F family. What makes it interesting is when we pair one of these 65 W parts against its 125 W overclocking counterpart, and if the extra base and turbo frequency boost is actually worth the money in an era where motherboards don't seem to care about power?

Intel’s Core i7-10700 at 65 W: Is It Really 65 W?

The understanding of the way that Intel references its TDP (thermal design point) values has gone through a mini-revolution in the last few years. We have had an almost-decade of quad-core processors at around 90 W and 65 W, and most of them would never reached these numbers even under turbo modes - for example, the Core i5-6600K was rated at 91 W, but peak power draw was only 83 W. This has been the norm for a while, until recently when Intel had to start boosting the core count. As we have slowly gone up in core count, from 4 to 6 to 8 and now 10, these numbers have seemed almost arbitrary for a while.

The reason comes down to what TDP really is. In the past, we used to assume that it was the peak power consumption of the processor was its TDP rating – after all, a ‘thermal design point’ of a processor was almost worthless if you didn’t account for the peak power dissipation. What makes Intel’s situation different (or confusing, depending on how you want to call it) is that the company defines its TDP in the context of a 'base' frequency. The TDP will be the maximum power under a sustained workload for which the base frequency is the minimum frequency guarantee. Intel defines a sustained workload one in which the 'turbo budget' has expired, and the processor will achieve its best frequency above base frequency (but not turbo modes).

The point about ‘not turbo’ is the key element here. Intel’s TDP ratings are only in effect for the base frequency, not the turbo frequency. If a PC is built with a maximum power dissipation in mind, allowing a processor to turbo above that power might have catastrophic consequences for the thermal performance of that system. The other angle is that Intel never quotes the turbo power levels (also known as Power Level 2, or PL2) alongside the other specifications, although they are technically in the specification documents when they get released.

On top of all this, motherboard manufacturers also get a say in how a processor performs. Because turbo power is only an optional suggestion from Intel, technically Intel will accept any value for the ceiling of the turbo power, and accept turbo under any circumstances if the motherboard manufacturer wants it.

Motherboard manufacturers overengineer their motherboards to support longer turbo times (or overclocking), and so they will often ignore these Intel recommended values for PL2, allowing the processor to turbo harder for longer, and in a lot of cases of premium motherboards, indefinitely.

So why does all this matter with respect for this review? Well my key comparison in this review is our new processor, the Core i7-10700, up against its overclocking counterpart, the Core i7-10700K. Aside from the suffix difference, the K variant has a TDP almost twice as high, and this manifests almost entirely in the base frequency difference.Even though the TDP is 125 W vs 65 W, the peak turbo frequency difference is only +300 MHz, and the all-core turbo difference is only +100 MHz. In contrast, the base frequency difference is +900 MHz, and that is ultimately what the user is paying for. But this base frequency only matters if the motherboard bothers to put a cap on turbo budgets.

The base frequency is more of a minimum guaranteed frequency, than an absolute 'this is what you will get' value under a sustained workload. Intel likes to state that the base frequency is the guarantee, however if a processor can achieve a higher frequency while power limited, it will - if it can achieve that power value with 200 MHz above base frequency, it will run at the higher frequency. If this sounds familiar, this is how all AMD Ryzen processors work, however Intel only implements it when turbo is no longer available. This ends up being very processor dependent. 

For the turbo, as mentioned, Intel has recommendations for power levels and turbo time in its documentation, however OEMs and motherboard manufacturers are free to routinely ignore it. This is no more obvious than when comparing these two processors. What does this mean for end-users? Well, graphs like this.
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