NotebookCheck Reviews the Intel Core Ultra 7 255U: A Deep Dive into Next-Gen Efficiency

NotebookCheck reported on November 15 that Intel’s new Core Ultra 7 255U processor has officially hit the market, but early results show significant performance variability compared with its predecessor, the Ultra 7 155U. According to the review, the real-world performance of this new chip depends heavily on each laptop’s thermal design and power-limit configuration.

The Core Ultra 7 255U, built on Intel’s latest Arrow Lake-U architecture, is positioned as the successor to last year’s Meteor Lake-U Ultra 7 155U and is now appearing in a wide range of new laptops. However, multiple tests indicate that the new processor does not consistently deliver the stable performance uplift many expected. Instead, results vary dramatically from one device to another.

NotebookCheck tested three laptops equipped with the Ultra 7 255U—the HP 17t-cn500, Lenovo ThinkPad T14s 2-in-1 Gen1, and Lenovo IdeaPad 5 2-in-1 16IAL10—and found that the improvements were far from uniform.

The most striking example came from the HP 17t. Among laptops using the same processor, it delivered the weakest results and exhibited a pronounced “performance cycling” issue during stress tests. This phenomenon causes the CPU clock speeds to swing sharply in cycles under sustained load, resulting in inconsistent performance and unstable frame rates when running games or demanding applications, severely impacting the user experience.

Performance cycling typically occurs when a processor hits thermal or power limits, forcing it to throttle repeatedly and creating noticeable fluctuations in performance.

Benchmark data shows that the Ultra 7 255U’s performance range is extremely wide. In the best-case scenario—such as in the Lenovo IdeaPad 5 2-in-1 16—the 255U outperformed the HP Envy 17 equipped with the older 155U by up to 50%, demonstrating the strength of the new architecture.

But in the worst-case scenario—seen in the HP 17t—the very same 255U ran nearly 20% slower than the 155U inside Lenovo’s ThinkPad E14 G6, creating an awkward situation where the new chip underperforms the previous generation.

These findings highlight a crucial takeaway: for modern mobile processors, a laptop’s cooling system and power-management tuning play a far more decisive role than the processor’s generation alone. Thermal performance, power limits, and throttling behavior have become key factors for consumers to consider—often more important than the CPU’s model name itself.