Core i5-8400H vs Core i5-8257U

Both the Core i5-8400H and Core i5-8257U share an identical 4-core/8-thread configuration. Boost clocks reach 4.2 GHz on the Core i5-8400H versus 3.9 GHz on the Core i5-8257U — a 7.4% clock advantage for the Core i5-8400H (base: 2.5 GHz vs 1.4 GHz). The Core i5-8400H uses the Coffee Lake-H (2018−2019) architecture (14 nm), while the Core i5-8257U uses Coffee Lake-U (2018−2019) (14 nm). In PassMark, the Core i5-8400H scores 7,456 against the Core i5-8257U's 7,427 — a 0.4% lead for the Core i5-8400H. Cinebench R23 multi-core: 4,657 vs 4,017 (14.8% advantage for the Core i5-8400H). Geekbench 6 single-core — the metric most relevant to gaming — records 1,493 vs 1,100, a 30.3% lead for the Core i5-8400H that directly translates to higher frame rates. Multi-core Geekbench: 4,963 vs 4,000 (21.5% advantage for the Core i5-8400H). L3 cache: 12 MB (total) on the Core i5-8400H vs 6 MB on the Core i5-8257U.

The Core i5-8400H uses the BGA1440 socket (PCIe 3.0), while the Core i5-8257U uses FCBGA1528 (PCIe 3.0) — making them incompatible on the same motherboard. Maximum memory speed reaches DDR4 2666 MHz on the Core i5-8400H versus DDR4-2400 on the Core i5-8257U — the Core i5-8400H supports 200% faster memory, which can translate to measurable gains in memory-sensitive workloads. The Core i5-8400H supports up to 64 GB of RAM compared to 32 GB — 66.7% more capacity for professional workloads. Both feature 2-channel memory with ECC support. Both provide 16 PCIe lanes. Chipset compatibility: Intel HM370,Intel QM370 (Core i5-8400H) and 300 Series (Core i5-8257U).

Neither processor supports overclocking. Virtualization support: true (Core i5-8400H) vs VT-x, VT-d (Core i5-8257U). Both include integrated graphics — Intel UHD Graphics 630 (Core i5-8400H) and Intel Iris Plus Graphics 645 (Core i5-8257U) — useful as a fallback for troubleshooting or display output without a dedicated GPU. Primary use case: Core i5-8400H targets Mobile, Core i5-8257U targets Ultrabook.