Intel Alder Lake-U Review - The fine line between Efficiency and insufficient Performance

The U-series Core i5 and Core i7 chips offer two fast Performance cores and eight Efficiency cores (total of 12 threads), so two performance cores fewer compared to most Alder Lake-P chips (like the Core i7-1260P). When such a processor can use a lot of energy, the two P-cores will reach very high clocks, but the efficiency quickly decreases above 4 GHz and the additional performance is low. The performance cores also consume a lot of power in single-core scenarios, which can quickly result in increased fan activity when you have a thin laptop with limited cooling capabilities, even in short peak load scenarios (when you launch an application, for example). We already noticed this behavior during some of our reviews and Alder Lake laptops tend to have more fan activity compared to similar last-gen laptops with 11th gen Tiger Lake CPUs.

We start with the single-core and multi-core performance of the Alder Lake-U laptops we have tested so far (Core i7, 15W PBP). Our efficiency measurements are performed with an external monitor attached so we can eliminate the influence of the integrated display.

Finally, we will compare two Alder Lake-U chips (Core i7-1255U in the Microsoft Surface Pro 9 & Core i7-1265U in the HP ZBook Firefly 14 G9) with the Core i7-1260P in the Lenovo ThinkPad T14 G3 as well as the Core i7-12700H in the HP ZBook Power 15 G9 at fixed power limits (adjusted via Throttle Stop software). We check the results at 15, 20, 28, 35, and 45W.

Please note that there can always be slight efficiency differences even when you have the same chips, but our results are still a good indicator. The Core i7-1255U in the Surface Pro 9, for instance, seems to be a very efficient chip, the Core i7-1260P in the ThinkPad T14 G3 on the other hand not.

After all our tests so far, it is evident that Intel’s P-cores currently have an advantage compared to AMD and Apple in terms of raw performance. However, the Core i7-1265U (4.7-4.8 GHz) requires around 21 Watts for the full single-core performance, while the Core i7-1255U (4.5-4.6 GHz) is a bit more efficient at 17-20 Watts. If a device does not manage this power level, the single-core performance is not better compared to the current AMD Ryzen 7 6800U or Apple's M2.

If the performance core can utilize its full potential, we can see an advantage of up to 20 % over the competition. All in all, the Alder Lake-U chips offers very good single-core performance and there is no disadvantage compared to the faster Alder Lake-P or even Alder Lake-H processors, even though the require a bit more power (~22-24W in our measurements).

A look at the efficiency shows that the Core i7-1255U performs very well and is even ahead of the AMD Ryzen 7 Pro 6850U. The Intel chip benefits from its lower maximum Turbo clocks compared to the Core i7-1265U and it is more efficient. Both the P- and H-series CPU fall behind du to their higher consumption figures. Apple is still miles ahead in terms of efficiency with a single-core consumption of little more than 5W on its current M2 processor.

Our multi-core tests show bigger differences, because the fastest Alder Lake-U (Core i7-1255U, Surface Pro 9) is 55 % faster than the supposedly superior Core i7-1265U in HP’s Elite Dragonfly G3. Intel only manages to keep up with AMD’s current U-series chips (usually running at 25W) in multi-core benchmarks with much more power. For comparison: The Core i7-1255U consumes almost 50W and the Core i7-1260P in the ThinkPad T14 G3 even more than 50W.

This is also evident when we look at the efficiency chart, where Apple's M2 is once again at the top followed by the AMD Ryzen chips. All the Alder Lake CPUs are falling behind.

One more aspect that should not be overlooked is that the efficiency results should even be a bit worse when Alder Lake-U and P CPUs are operated at high power limits, because the power adapters are sometimes a limitation. This means the laptops has to use the internal battery for a short time as well to cover the high power consumption. We measure the power consumption at the PSU, so this aspect is not included in our measurements.

We want to find out the optimal power range for the Alder Lake-U processors and when it makes sense to use an Alder Lake-P chip with two additional performance cores. For this test, we used the following four processors at locked power limits (via Throttle Stop): Core i7-1255U, Core i7-1265U, Core i7-1260P & Core i7-12700H.

The two U-series CPUs have a slight advantage running at 15W, both in single-core as well as multi-core scenarios. However, the gap is not huge and the lower core clocks are almost balanced by the higher core count, even at 15W.

The single-core performance of the four processors is virtually identical at 20W and only the Core i7-1255U can maintain a small advantage in multi-core tests.

Our tests at 28W show that the Core i7-1255U does not manage higher single-core results. Thanks to its slightly lower Turbo clocks, it can already utilize its full single-core performance at 20W while the other three processors can improve their scores a bit (consumption between 21-25W). The Core i7-12700H already has an advantage over the Core i7-1260P, which is also faster than the two U-series chips. We can conclude that it does not make much sense to use an Alder Lake-U processor in a laptop where the cooling solution can handle 25W.

The disadvantage of the Alder Lake-U processors is getting even bigger at 35W, while the Core i7-12700H can increase the gap over the Core i7-1260P.

Running at 45W clearly shows a big difference between the CPUs and that the cores are very inefficient at very high clocks. Compared to 35W, the Core i7-1255U (we could not test the i7-1265U at sustained 45W) is only 4% faster despite 28% more energy. The decision between the Core i7-1260P and the Core i7-12700H is also very simple since the H-series CPU has a big advantage thanks to its six P-cores.

Our measurements and benchmark scores show that Alder Lake-U processors can make sense, but both Intel as well as notebook manufacturers make it rather difficult for the customer. There are multiple factors for this, starting with the sheer number of Intel CPUs in the mobile segment. Intel should also specify a smaller TDP range and better differentiate the CPU classes. It just does not make much sense to run a Core i7-1255U at 50W when a Core i7-1260P can be limited to 25 or just 20 Watts (in the case of the Samsung Galaxy Book2). Stricter limitations could avoid this issue completely. The U-series CPUs could be limited in the range between 15-25W, the P-series between 25-40W and the H-series could start at 40W.

The notebook manufacturers should pay more attention as well. It does not make much sense to run a U-series CPU at up to 55W only because its possibly. The additional energy is pretty much wasted, but results in more fan activity. We have clearly shown that you will hardly lose any performance with reduced power limits, but the user will benefit from lower emissions in return.

The wide range of power settings is a problem for users, because the CPU performance can vary by wide margins. The Alder Lake-U processors work the best up to 25 Watts, and manufacturers should switch to Alder Lake-P chips when the cooling can handle more heat. AMD’s U-series processors are much more efficient in multi-core scenarios, but the availability is still limited.

Compared to AMD (like the Ryzen 7 6800U), Intel still has a performance advantage in single-core load scenarios. However, AMD is usually ahead in multi-core tests, especially when you look at the efficiency. Apple is still in a completely different league with its M1 and M2 CPUs, especially when you only stress one core. Both AMD and Apple also have an advantage in terms of iGPU performance compared to the familiar Intel Iris Xe Graphics G7.

Intel has already announced its new Raptor Lake processor line-up ad we expect the first laptops in the next couple of weeks. However, there are no major changes for the mobile processors (U P & H-series) except for some clock improvements. The other specs including the number of cores, the integrated GPU as well as the power limits are identical. There are some optional additional features, but we only expect small improvements in terms of performance and efficiency.