Core i5-1240U vs Core i7-8700K

The Core i5-1240U packs 10 cores / 12 threads, while the Core i7-8700K offers 6 cores / 12 threads — the Core i5-1240U has 4 more cores. Boost clocks reach 4.4 GHz on the Core i5-1240U versus 4.7 GHz on the Core i7-8700K — a 6.6% clock advantage for the Core i7-8700K (base: 1.1 GHz vs 3.7 GHz). The Core i5-1240U uses the Alder Lake-U (2022) architecture (Intel 7 nm), while the Core i7-8700K uses Coffee Lake-S (2017−2018) (14 nm). In PassMark, the Core i5-1240U scores 13,387 against the Core i7-8700K's 13,572 — a 1.4% lead for the Core i7-8700K. L3 cache: 12 MB (total) on the Core i5-1240U vs 12288 kB on the Core i7-8700K.

The Core i5-1240U uses the FCBGA1781 socket (PCIe 5.0), while the Core i7-8700K uses LGA1151 (PCIe 3.0) — making them incompatible on the same motherboard. Maximum memory speed reaches LPDDR5-5200 on the Core i5-1240U versus DDR4-2666 on the Core i7-8700K — the Core i5-1240U supports 22.2% faster memory, which can translate to measurable gains in memory-sensitive workloads. The Core i7-8700K supports up to 128 GB of RAM compared to 64 GB — 66.7% more capacity for professional workloads. Both feature 2-channel memory with ECC support. PCIe lanes: 14 (Core i5-1240U) vs 16 (Core i7-8700K) — the Core i7-8700K offers 2 more lanes for additional GPUs or NVMe drives.

Virtualization: VT-x, VT-d, EPT (Core i5-1240U) / not specified (Core i7-8700K). Both include integrated graphics — Iris Xe Graphics 80EU (Core i5-1240U) and Intel UHD Graphics 630 (Core i7-8700K) — useful as a fallback for troubleshooting or display output without a dedicated GPU. Primary use case: Core i5-1240U targets Thin & Light Laptop. Direct competitor: Core i5-1240U rivals Ryzen 5 5600U.