Intel Core i5-8279U vs Intel Core i5-8400H Comparison

Head-to-Head Benchmarks

The recorded data shows a clear pattern: the Intel Core i5-8400H takes seven of the eight head-to-head benchmark comparisons, while the Intel Core i5-8279U manages a single, notable victory. The margins are generally narrow, but the consistency of the 8400H's wins points to a robust performance profile across most workloads.

Starting with Cinebench, the 8400H leads in every single iteration. In Cinebench R15 multi-core, the 8400H scores 644 against the 8279U's 634, a 1.6% advantage. The single-core R15 result is nearly identical in percentage terms, with the 8400H scoring 90 versus 89, a 1.1% lead. Moving to Cinebench R20, the pattern holds: the 8400H posts 2684 multi-core and 378 single-core, while the 8279U posts 2643 and 372, respectively. Both margins sit at 1.6%. In Cinebench R23, the delta remains consistent at 1.6% for both tests, with the 8400H scoring 6392 multi-core and 902 single-core, against the 8279U's 6294 and 888.

The Geekbench results tell a more nuanced story. In Geekbench single-core, the 8400H wins decisively with a score of 1281 versus 1209, a substantial 6% advantage. This is the largest performance gap recorded in the entire head-to-head set. However, the 8279U strikes back in Geekbench multi-core, scoring 3764 against the 8400H's 3656. This is a 2.9% win for the 8279U, and it is the only test where the 8400H does not come out ahead.

So, what does this mean in practice? The 8400H is consistently ahead in pure CPU rendering and compute tasks as measured by Cinebench, and it has a significant edge in single-threaded Geekbench performance. The 8279U's win in Geekbench multi-core is curious, as it contradicts the Cinebench multi-core results. This could suggest different workload scaling or memory bandwidth influences, but the data only shows the scores. It is worth remembering the average benchmark score across all tests favors the 8400H, which sits at 2003, compared to the 8279U's 1987.

FAQ

Q: Which processor has the higher boost clock?

A: Both processors share the same boost clock of 4.10 GHz.

Q: Does the Intel Core i5-8279U support more memory bandwidth?

A: Yes, the database lists the 8279U with a memory bandwidth of 34.1 GB/s, while the 8400H has no listed memory bandwidth figure.

Q: What is the transistor count for each processor?

A: The Intel Core i5-8279U has a transistor count of 2,300 million, while the Intel Core i5-8400H does not have a transistor count recorded in the database.

Q: Which processor has a larger L3 cache?

A: The Intel Core i5-8400H has a shared L3 cache of 12 MB, whereas the Intel Core i5-8279U has a shared L3 cache of 6 MB.

Q: How do their overall benchmark averages compare?

A: The Intel Core i5-8400H has an average benchmark score of 2003, while the Intel Core i5-8279U has an average score of 1987.

Q: Are both processors unlocked for overclocking?

A: No, neither processor has an unlocked multiplier.

Architecture Differences

Both processors are built on Intel's Coffee Lake architecture and use the same 14 nm process node, but they belong to different sub-families. The Intel Core i5-8400H is part of the Coffee Lake-H lineup, intended for high-performance mobile systems, while the Intel Core i5-8279U is part of the Coffee Lake-U lineup, designed for more power-efficient ultraportable devices.

The core layout is identical in terms of count: both have 4 cores and 8 threads. The L1 and L2 caches are also the same, with 64 KB per core and 256 KB per core, respectively. The key architectural divergence lies in the L3 cache. The 8400H features a 12 MB shared L3 cache, while the 8279U is limited to 6 MB. This is a substantial difference, and it likely explains why the 8400H performs better in sustained multi-threaded rendering workloads, as it can hold more working data on-die.

Another significant architectural difference is the integrated graphics solution. The 8400H comes with the UHD 630, while the 8279U steps up to the Iris Pro Plus 655. While the database does not include specific graphics benchmarks, the presence of the Iris Pro Plus 655 suggests a stronger iGPU for the 8279U.

The socket also differs. The 8400H uses Intel BGA 1440, while the 8279U uses Intel BGA 1526. This means the two processors are not interchangeable in the same motherboard. The die size is identical at 126 mm², and both are produced by Intel. The 8279U has a listed transistor count of 2,300 million, but no such figure is recorded for the 8400H, so a direct comparison on that front is not possible from the data.

Specification Differences

The specification sheet shows several key differences beyond the architecture. The most obvious is the thermal design power (TDP). The Intel Core i5-8400H has a TDP of 45 watts, while the Intel Core i5-8279U has a TDP of 28 watts. This 17-watt gap is significant; the 8400H is likely intended for bulkier laptops with better cooling, while the 8279U can fit into slimmer chassis.

Base clock speeds differ slightly. The 8400H has a base clock of 2.50 GHz, while the 8279U sits at 2.40 GHz. The boost clock is identical at 4.10 GHz for both, which explains why the single-core performance is so close.

Memory support is listed as DDR4 for both, but the 8279U has additional details: it supports dual-channel memory with a bandwidth of 34.1 GB/s. The 8400H has no memory bus or bandwidth information in the database. The 8279U also has PCIe information listed as Gen 3 with 16 lanes (CPU only), while the 8400H has no PCIe data recorded.

The integrated graphics differ, as mentioned: UHD 630 for the 8400H versus Iris Pro Plus 655 for the 8279U. The release dates are different as well; the 8400H launched in 2018, while the 8279U launched in 2019. The 8279U has a launch MSRP of $320. Both processors are marked as end-of-life in terms of production status, and neither has an unlocked multiplier.

The Verdict

Looking strictly at the recorded data, the Intel Core i5-8400H is the stronger performer in the majority of tests. It wins seven out of eight head-to-head comparisons, including all six Cinebench tests and Geekbench single-core. Its advantage in Geekbench single-core is a notable 6%, and its Cinebench margins are consistently around 1.6%. The overall average benchmark score also favors the 8400H, at 2003 versus 1987.

However, the 8279U is not without merit. It wins in Geekbench multi-core by 2.9%, which suggests it may handle certain multi-threaded tasks better than the Cinebench scores imply. Additionally, its lower TDP of 28 watts versus 45 watts makes it a more suitable choice for thin-and-light laptops where thermals and battery life are priorities. The 8279U also has the stronger integrated graphics on paper, with the Iris Pro Plus 655.

For a user who prioritizes raw CPU throughput in rendering and single-threaded applications, the 8400H is the clear pick from the data. For a user who needs a more power-efficient processor for a portable device, and who may benefit from the superior iGPU and the Geekbench multi-core win, the 8279U is the logical choice. The 8400H's larger 12 MB L3 cache likely contributes to its Cinebench dominance, but the 8279U's dual-channel memory support and higher memory bandwidth could be why it wins in Geekbench multi-core.

Where Each One Wins

Intel Core i5-8400H: This processor wins in all Cinebench R15, R20, and R23 tests, both single-core and multi-core. The margins are small but consistent, with a 1.6% lead in multi-core and a 1.1% to 1.6% lead in single-core across versions. It also wins decisively in Geekbench single-core, with a 6% advantage. This makes it the better choice for CPU rendering, video encoding, and any application that relies heavily on single-threaded performance. The 12 MB L3 cache is a likely factor in these victories. Its higher TDP suggests it is intended for systems that can sustain higher power draw for longer periods, which is beneficial for extended workloads.

Intel Core i5-8279U: This processor wins in Geekbench multi-core, outscoring the 8400H by 2.9%. This single victory indicates that in some multi-threaded workloads, particularly those modeled by Geekbench, the 8279U can pull ahead. Its advantages lie in efficiency: a 28 watt TDP versus 45 watts, a dual-channel memory bus with 34.1 GB/s bandwidth, and the Iris Pro Plus 655 integrated graphics. For a user who prioritizes battery life, portability, and graphics performance without a dedicated GPU, the 8279U is the stronger option. The data does not show a scenario where the 8279U wins in Cinebench, so its multi-core win is specific to the Geekbench test methodology.