Intel Core i5-8400 vs Intel Core i7-1250U Comparison

The Intel Core i7-1250U and Intel Core i5-8400 occupy different corners of the processor market. The i7-1250U is a mobile Alder Lake chip with 10 cores and 12 threads, a 9W TDP, and a boost clock of 4.70 GHz. The i5-8400 is a desktop Coffee Lake part with 6 cores and 6 threads, a 65W TDP, and a 4.00 GHz boost. In head-to-head testing, the i7-1250U wins 15 of 19 benchmarks, while the i5-8400 takes 4. Both sit at the 68th percentile of all CPUs, but the i7-1250U posts a higher average benchmark score of 13351 versus 12765 for the i5-8400.

Where Each One Wins

The i7-1250U is the clear winner in single-thread and math-heavy workloads. It leads Cinebench R15 singlecore by 103.6%, Cinebench R23 singlecore by 42.2%, and Passmark integer math by 57.7%. It also dominates data encryption by 170.6%, making it a strong pick for encryption tasks. The i5-8400, however, wins in extended instructions by 43.7%, random string sorting by 14.8%, data compression by 8.2%, and Cinebench R23 multicore by 9.9%. If your work involves compression or extended instruction sets, the i5-8400 has a measurable edge. For general productivity, the i7-1250U is ahead in most tests, including Geekbench multicore by 13.5% and Passmark multithread by 22.8%.

Architecture Differences

The two chips come from different generations and process nodes. The i7-1250U uses Intel's 10 nm Alder Lake architecture, while the i5-8400 uses the 14 nm Coffee Lake design. Core counts differ: the i7-1250U has 10 cores and 12 threads, the i5-8400 has 6 cores and 6 threads. Cache layouts also diverge. The i7-1250U has 80 KB of L1 per core, 1.25 MB of L2 per core, and 12 MB of shared L3. The i5-8400 has 64 KB L1 per core, 256 KB L2 per core, and 9 MB of shared L3. Memory support is another split: the i7-1250U accepts both DDR4 and DDR5, while the i5-8400 is limited to DDR4. PCIe connectivity differs as well, with the i7-1250U on Gen 4 and the i5-8400 on Gen 3 with 16 lanes. Integrated graphics are not equal: the i7-1250U carries Iris Xe 96EU, the i5-8400 has UHD Graphics 630. The i7-1250U is a mobile part on Intel BGA 1781, while the i5-8400 is a desktop chip on Socket 1151. The i5-8400 has a die size of 154 mm² and a memory bandwidth of 42.7 GB/s; the i7-1250U does not list those figures. Production status also differs: the i7-1250U is active, the i5-8400 is end-of-life. Release dates are 2022-02-22 for the i7-1250U and 2017-10-04 for the i5-8400. The i5-8400 has a part number SLAPL and a launch MSRP of $182; the i7-1250U has neither listed.

Head-to-Head Benchmarks

The i7-1250U wins the majority of tests, often by large margins. Its biggest victory is in Passmark data encryption, where it leads by 170.6%. Cinebench R15 singlecore shows a 103.6% advantage, and Passmark find prime numbers is 56.8% ahead. Integer math is 57.7% higher, and Cinebench R15 multicore is 48.5% ahead. Cinebench R23 singlecore is 42.2% better, and Passmark physics is 38.7% higher. Floating point math is 21% ahead, Cinebench R20 multicore is 20.9% ahead, and Cinebench R20 singlecore is 21.1% ahead. Geekbench multicore is 13.5% higher, Geekbench singlecore is 22.8% higher, and Passmark multithread is 22.8% higher. Passmark single thread is 14% ahead.

The i5-8400 wins four tests. Its largest lead is in Passmark extended instructions, where it is 43.7% ahead. Random string sorting is 14.8% better, data compression is 8.2% better, and Cinebench R23 multicore is 9.9% better. These wins are concentrated in specific instruction-heavy and compression workloads, not in general compute.

The Verdict

The data points to the i7-1250U as the better all-round performer. It wins 15 of 19 head-to-head tests, with particularly strong showings in single-thread, encryption, and integer math. The i5-8400 is a desktop part with a higher TDP and a narrower set of strengths. If you need a mobile chip with low power draw and strong single-thread performance, the i7-1250U is the clear choice. If you are building a desktop and your workload involves extended instructions or data compression, the i5-8400 has a measurable advantage. The i5-8400 is also end-of-life, while the i7-1250U remains active. For most users, the i7-1250U is the safer pick.

FAQ

Q: Which CPU has more cores?

A: The i7-1250U has 10 cores and 12 threads, while the i5-8400 has 6 cores and 6 threads.

Q: Which CPU has a higher boost clock?

A: The i7-1250U boosts to 4.70 GHz, the i5-8400 to 4.00 GHz.

Q: Which CPU supports DDR5 memory?

A: The i7-1250U supports both DDR4 and DDR5, while the i5-8400 supports only DDR4.

Q: Which CPU has a larger L3 cache?

A: The i7-1250U has 12 MB of shared L3, the i5-8400 has 9 MB.

Q: Which CPU is still in production?

A: The i7-1250U is active, while the i5-8400 is end-of-life.

Q: What is the TDP difference?

A: The i7-1250U has a 9W TDP, the i5-8400 has a 65W TDP.

Specification Differences

| Field | Intel Core i7-1250U | Intel Core i5-8400 |

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

| Cores | 10 | 6 |

| Threads | 12 | 6 |

| Base Clock | 1100.00 MHz | 2.80 GHz |

| Boost Clock | 4.70 GHz | 4.00 GHz |

| TDP | 9 W | 65 W |

| Socket | Intel BGA 1781 | Intel Socket 1151 |

| Architecture | Alder Lake | Coffee Lake |

| Codename | Alder Lake-U | Coffee Lake |

| Process Node | 10 nm | 14 nm |

| Die Size | Not listed | 154 mm² |

| L1 Cache | 80 KB (per core) | 64 KB (per core) |

| L2 Cache | 1.25 MB (per core) | 256 KB (per core) |

| L3 Cache | 12 MB (shared) | 9 MB (shared) |

| Memory Support | DDR4, DDR5 | DDR4 |

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

| PCIe | Gen 4 | Gen 3, 16 Lanes (CPU only) |

| Integrated Graphics | Iris Xe 96EU | UHD Graphics 630 |

| Market Segment | Mobile | Desktop |

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

| Release Date | 2022-02-22 | 2017-10-04 |

| Launch MSRP | Not listed | $182 |

| Part Number | Not listed | SLAPL |