Intel Core Ultra 7 255H vs AMD Ryzen 7 8840HX

Intel Core Ultra 7 255H

The Intel Core Ultra 7 255H is a mobile high-end CPU for larger notebooks based on the Arrow Lake architecture. It offers 16 cores consisting of 6 fast performance cores (Lion Cove) with up to 5.1 GHz and 8 smaller efficiency cores (Skymont) with up to 4.4 GHz clock speed and two additional "low power" efficiency cores with up to 2.5 GHz (Skymont). The CPU has access to 24 MB of cache and is specified with a TDP of 28 watt (PL1, 115W PL2).

The SoC integrates a small dedicated NPU called AI Boost with 13 TOPS (Int8) and optionally supports vPro Essentials. The integrated memory controller supports up to 192 GB LPDDR5/x-8400 or DDR5-6400 (dual channel). The integrated GPU (iGPU) is an Intel Arc 140T graphics card which offers eight Xe cores with up to 2.25 GHz.

Performance - High End

The Core Ultra 7 is superior to the top model Core Ultra 9 285H as only the maximum Turbo frequency is 200 MHz lower. Due to the improved IPC of the cores (especially the efficiency cores), the CPU should perform slightly below the level of the old Raptor Lake Core Core 9 270H (6 + 8 cores, max 5.8 / 4.1 GHz). This makes the CPU very suitable for demanding tasks such as high-end gaming and content creation.

Chiplet design

Like the desktop and HX chips, the Arrow Lake-H chips are based on individual chiplets that are placed on a 22nm base tile from Intel using Foveros 3D packaging. The CPU part comes from TSMC using the modern N3B (3nm) process. As with HX, the GPU also is produced at TSMC and is manufactured using the N5P process. SoC and I/O Tile are also from TSMC but in the older N6 process.

AMD Ryzen 7 8840HX

The AMD Ryzen 7 8840HX is a higher-end 12-core Dragon Range refresh lineup processor that debuted in April 2025 and is primarily targeted at gaming laptops. The product offers 12 SMT-enabled Zen 4 cores (24 threads) running at 2.9 GHz to 5.1 GHz, along with a rather basic Radeon 610M RDNA 2 architecture iGPU. This Ryzen 7 8000 APU is essentially a Ryzen 9 7845HX with the base clock speed and Turbo clock speed cut by 100 MHz each.

The 8840HX is composed of three dies made on two different nodes (5 nm for CPU cores; 6 nm for other componentry). It features a very healthy 28 PCIe 5 lanes for connecting graphics cards and SSDs as fast as 15.75 GB/s. The RAM controller is limited to DDR5-5200 or slower; there is no NPU and no Thunderbolt support, the product page on amd.com indicates, but the clock multiplier is unlocked for easy overclocking.

Performance

While we have not tested a single system featuring the 8840HX as of April 2025, we can take the 7845HX's multi-thread Cinebench scores and lower them by a percent or two. If we do that, the 8840HX emerges as a Core i7-14650HX and Core i7-14700HX-beating CPU which is fast enough for any 2025 or 2026 game.

Power consumption

Much like the 7845HX, the 8840HX has a base TDP (long-term power limit) of 55 watts that can officially be jacked up to as high as 75 watts. In fact, Alienware allows the 7845HX to consume well over 100 watts in its 2023 Alienware m16 (the only 7845HX system Notebookcheck has tested). Either way, to dissipate 50+ watts, at least one high-RPM fan is needed.