Core i3-8121U vs Core i5-3475S

The Core i3-8121U packs 2 cores / 4 threads, while the Core i5-3475S offers 4 cores / 4 threads — the Core i5-3475S has 2 more cores. Boost clocks reach 3.2 GHz on the Core i3-8121U versus 3.6 GHz on the Core i5-3475S — a 11.8% clock advantage for the Core i5-3475S (base: 2.2 GHz vs 2.9 GHz). The Core i3-8121U uses the Coffee Lake-U (2018−2019) architecture (10 nm), while the Core i5-3475S uses Ivy Bridge (2012−2013) (22 nm). In PassMark, the Core i3-8121U scores 4,271 against the Core i5-3475S's 4,315 — a 1% lead for the Core i5-3475S. Geekbench 6 single-core — the metric most relevant to gaming — records 1,178 vs 705, a 50.2% lead for the Core i3-8121U that directly translates to higher frame rates. Multi-core Geekbench: 2,250 vs 1,544 (37.2% advantage for the Core i3-8121U). L3 cache: 4 MB (total) on the Core i3-8121U vs 6 MB (total) on the Core i5-3475S.

The Core i3-8121U uses the BGA1440 socket (PCIe 3.0), while the Core i5-3475S uses LGA1155 (PCIe 3.0) — making them incompatible on the same motherboard. Maximum memory speed reaches DDR4-2400 on the Core i3-8121U versus DDR3-1600 on the Core i5-3475S — the Core i3-8121U supports 28.6% faster memory, which can translate to measurable gains in memory-sensitive workloads. Both support up to 32 GB of RAM. Both feature 2-channel memory with ECC support. Both provide 16 PCIe lanes. Chipset compatibility: SoC (Core i3-8121U) and H61,B75,H77,Z75,Z77 (Core i5-3475S).

Neither processor supports overclocking. Only the Core i3-8121U supports AVX-512 instructions — important for machine learning and scientific applications. Both support VT-x, VT-d, EPT virtualization. The Core i5-3475S includes integrated graphics (HD Graphics 4000), while the Core i3-8121U requires a dedicated GPU. Primary use case: Core i3-8121U targets Productivity, Core i5-3475S targets Budget. Direct competitor: Core i3-8121U rivals Core i3-8130U; Core i5-3475S rivals FX-6300.