Core i5-5257U vs Core i5-4278U

Both the Core i5-5257U and Core i5-4278U share an identical 2-core/4-thread configuration. Boost clocks reach 3.1 GHz on the Core i5-5257U versus 3.1 GHz on the Core i5-4278U — identical boost frequencies (base: 2.7 GHz vs 2.6 GHz). The Core i5-5257U uses the Broadwell-U (2015) architecture (14 nm), while the Core i5-4278U uses Haswell (2013−2015) (22 nm). In PassMark, the Core i5-5257U scores 2,837 against the Core i5-4278U's 2,826 — a 0.4% lead for the Core i5-5257U. Geekbench 6 single-core — the metric most relevant to gaming — records 950 vs 889, a 6.6% lead for the Core i5-5257U that directly translates to higher frame rates. Multi-core Geekbench: 1,900 vs 1,860 (2.1% advantage for the Core i5-5257U). L3 cache: 3 MB (total) on the Core i5-5257U vs 3 MB on the Core i5-4278U.

Both processors use the FCBGA1168 socket with PCIe 3.0. Maximum memory speed reaches LPDDR3 1866 MHz on the Core i5-5257U versus DDR3L-1600 on the Core i5-4278U — the Core i5-5257U supports 200% faster memory, which can translate to measurable gains in memory-sensitive workloads. Both support up to 16 GB of RAM. Both feature 2-channel memory with ECC support. Both provide 12 PCIe lanes. Chipset compatibility: Broadwell-U (Core i5-5257U) and Intel HM86,Intel HM87,Intel QM87 (Core i5-4278U).

Both support true virtualization. Both include integrated graphics — Intel Iris Graphics 6100 (Core i5-5257U) and Intel Iris Graphics 5100 (Core i5-4278U) — useful as a fallback for troubleshooting or display output without a dedicated GPU. Primary use case: Core i5-5257U targets Mobile.