Intel Core i5-9400 vs Intel Core i7-8559U Comparison

The Intel Core i5-9400 and Intel Core i7-8559U are two very different processors that happen to land at nearly the same overall performance level. The i5-9400 is a desktop chip built for sustained, multi-threaded workloads, while the i7-8559U is a mobile chip designed to deliver high single-thread performance in a compact form factor. Based on the benchmark data, the i7-8559U wins the majority of tests, but the i5-9400 takes a commanding lead in one critical area. Both chips sit at the 47th percentile of all CPUs, with average benchmark scores of 2254 for the i5-9400 and 2225 for the i7-8559U, making them near-peers in overall performance.

The Verdict

The data points to a clear split: the Intel Core i7-8559U is the better choice for users who prioritize raw speed in single-threaded and lightly-threaded applications. It wins every Cinebench test in the head-to-head comparison, including a 5.3% lead in Cinebench R20 single-core (414 vs 392) and a 5.1% lead in Cinebench R23 multi-core (6984 vs 6629). Its 4.50 GHz boost clock gives it a noticeable edge in burst workloads like gaming, web browsing, and everyday productivity tasks that rely on one or two cores.

The Intel Core i5-9400 is the better pick for Geekbench-style workloads, where it wins multi-core by a massive 19.8% (5141 vs 4293) and single-core by a slim 0.4% (1389 vs 1384). This suggests that in certain test suites, the i5-9400's six physical cores can outperform the i7-8559U's four cores with eight threads. However, given that the i7-8559U wins 6 of the 8 head-to-head benchmarks, the mobile chip is the more consistent performer overall.

For a desktop builder who needs a cheap, capable CPU for multi-threaded rendering tasks that use Geekbench-style scaling, the i5-9400 is the safer bet. For anyone building a compact system or upgrading a laptop, the i7-8559U's higher boost clock and lower power draw make it the obvious winner, even though it is a mobile part.

Architecture Differences

The two processors come from different Intel families. The i5-9400 is built on Coffee Lake, specifically the Coffee Lake Refresh generation, using a 14 nm process node. The i7-8559U is from the Kaby Lake family, specifically Kaby Lake-R, also on a 14 nm node but with the codename Kaby Lake-U Refresh. Both are manufactured by Intel, but they target different market segments: the i5-9400 is a Desktop part, while the i7-8559U is a Mobile part.

Core counts differ significantly. The i5-9400 has 6 cores and 6 threads, meaning no hyper-threading. The i7-8559U has 4 cores and 8 threads, using hyper-threading to double its thread count. This gives the i7-8559U a threading advantage in workloads that can use more than 6 threads, despite having fewer physical cores.

The i5-9400 has a base clock of 2.90 GHz and a boost clock of 4.10 GHz, while the i7-8559U has a lower base clock of 2.70 GHz but a higher boost clock of 4.50 GHz. The i5-9400 has a TDP of 65 W, whereas the i7-8559U is much more power-efficient at 28 W. Cache sizes also differ: the i5-9400 has 9 MB of shared L3 cache, while the i7-8559U has 8 MB. Both have 64 KB of L1 and 256 KB of L2 per core.

Integrated graphics are another differentiator. The i5-9400 uses UHD 630, while the i7-8559U features Iris Pro Plus, a more capable integrated solution for a mobile chip. The i5-9400 supports DDR4 memory on a dual-channel bus with a bandwidth of 42.7 GB/s, while the i7-8559U also supports DDR4 but the data does not specify its memory bus or bandwidth. The i5-9400 has PCIe Gen 3 with 16 lanes (CPU only), while no PCIe information is provided for the i7-8559U.

FAQ

Q: Which CPU is faster in single-threaded performance?

A: The Intel Core i7-8559U is faster in every single-threaded benchmark. It scores 99 in Cinebench R15 single-core vs 94 for the i5-9400, 414 vs 392 in Cinebench R20, and 986 vs 935 in Cinebench R23. This is a consistent 5.1% to 5.3% advantage across all three tests.

Q: Does the i5-9400 win any benchmarks?

A: Yes, the i5-9400 wins both Geekbench tests. It leads multi-core by 19.8% (5141 vs 4293) and single-core by a tiny 0.4% (1389 vs 1384). These are the only two wins out of eight head-to-head benchmarks.

Q: Why does the i7-8559U beat the i5-9400 in Cinebench multi-core despite having fewer cores?

A: The i7-8559U has 8 threads from 4 cores, while the i5-9400 has 6 threads from 6 cores. In Cinebench R23 multi-core, the i7-8559U scores 6984 vs 6629 for the i5-9400, a 5.1% lead. The higher boost clock of 4.50 GHz and hyper-threading likely compensate for the lower core count.

Q: Which chip is more power-efficient?

A: The data shows the i7-8559U has a TDP of 28 W, while the i5-9400 has a TDP of 65 W. This makes the i7-8559U significantly more power-efficient, drawing less than half the power of the desktop part.

Q: Are these CPUs still in production?

A: No, the i5-9400 is marked as end-of-life, while the i7-8559U is listed as active production status. The i5-9400 was released on 2018-10-18, and the i7-8559U was released earlier on 2018-04-04.

Q: Which CPU has better integrated graphics?

A: The i7-8559U has Iris Pro Plus, while the i5-9400 has UHD 630. For a mobile chip, the Iris Pro Plus is generally considered more capable, though the data does not provide specific performance numbers for either.

Specification Differences

| Specification | Intel Core i5-9400 | Intel Core i7-8559U |

|---|---|---|

| Cores | 6 | 4 |

| Threads | 6 | 8 |

| Base Clock | 2.90 GHz | 2.70 GHz |

| Boost Clock | 4.10 GHz | 4.50 GHz |

| TDP | 65 W | 28 W |

| Socket | Intel Socket 1151 | Intel BGA 1356 |

| Architecture | Coffee Lake | Kaby Lake |

| Codename | Coffee Lake | Kaby Lake-R |

| Generation | Core i5 (Coffee Lake Refresh) | Core i7 (Kaby Lake-U Refresh) |

| Die Size | Not specified | 123 mm² |

| L3 Cache | 9 MB (shared) | 8 MB (shared) |

| Memory Bus | Dual-channel | Not specified |

| Memory Bandwidth | 42.7 GB/s | Not specified |

| PCIe | Gen 3, 16 Lanes (CPU only) | Not specified |

| Integrated Graphics | UHD 630 | Iris Pro Plus |

| Market Segment | Desktop | Mobile |

| Production Status | End-of-life | Active |

| Release Date | 2018-10-18 | 2018-04-04 |

Head-to-Head Benchmarks

The i7-8559U dominates the Cinebench suite. In Cinebench R15 multi-core, it scores 703 vs 668, a 5% lead. Single-core R15 shows a similar gap: 99 vs 94, a 5.1% advantage. Moving to Cinebench R20, the i7-8559U wins multi-core with 2933 vs 2784 (5.1% ahead) and single-core with 414 vs 392 (5.3% ahead). In Cinebench R23, the pattern holds: multi-core is 6984 vs 6629 (5.1% ahead), and single-core is 986 vs 935 (5.2% ahead). This shows remarkable consistency — the i7-8559U is roughly 5% faster across all Cinebench workloads, regardless of core count.

The i5-9400 makes its stand in Geekbench. The multi-core result is a decisive victory: 5141 vs 4293, a 19.8% lead. This is the largest delta in the entire comparison. Single-core Geekbench is much closer, with the i5-9400 edging out the i7-8559U by just 0.4% (1389 vs 1384). These results suggest that the i5-9400's six physical cores are better utilized in the Geekbench multi-core test, which may scale differently than Cinebench's threading model.

Looking at overall averages, the i5-9400 has an average benchmark score of 2254, while the i7-8559U sits at 2225. The i5-9400's nearest rivals include the Intel Core i7-1068NG7 (2259, -0.2%), the Intel Core i7-10710U (2248, 0.3%), and the AMD Ryzen 5 PRO 1500 (2246, 0.4%). The i7-8559U's nearest rivals include the Intel Core i7-5775C (2224, 0%), the Intel Xeon E5-4648 v3 (2227, -0.1%), and the Intel Xeon D-1548 (2231, -0.3%). These numbers place both CPUs in a tight performance band, with the i5-9400 marginally ahead on average.

Where Each One Wins

The i7-8559U wins in any workload that benefits from high single-thread speed or efficient multi-threading. Its 4.50 GHz boost clock is the key advantage. In Cinebench — a standard for rendering and 3D modeling — it beats the i5-9400 in all six tests, including multi-core tests where it might be expected to lose due to having fewer physical cores. The 8 threads help it keep pace and even outpace the 6-thread i5-9400. For gaming, where single-core performance is often the bottleneck, the i7-8559U's 5%+ lead in Cinebench single-core scores suggests it will deliver smoother frame pacing in CPU-bound titles.

The i5-9400 wins in Geekbench, particularly in multi-core where it is nearly 20% ahead. This points to workloads that scale linearly with physical cores, such as certain video encoding, compilation, or scientific computing tasks. The 0.4% single-core win in Geekbench is negligible, but the multi-core margin is substantial. For a desktop user who runs applications that use Geekbench-style scaling, the i5-9400 offers a significant performance advantage. Additionally, the i5-9400's 65 W TDP is higher, but in a desktop chassis this is manageable with a capable air cooler, and the 6 cores may be more stable under sustained load compared to a mobile chip in a thin laptop.

The production status also matters. The i7-8559U is listed as active, meaning it may still be available for new builds or replacements. The i5-9400 is end-of-life, so it is likely only available on the used market. If you need a chip that is still in production, the i7-8559U is the only option here. For a mobile system, the i7-8559U is the clear winner due to its lower power draw and higher boost clock. For a desktop system, the i5-9400's Geekbench multi-core performance is a compelling reason to choose it, but only if your software behaves like Geekbench rather than Cinebench.