Intel Core i5-8279U vs Intel Core i5-8400T Comparison

Head-to-Head Benchmarks

The benchmark data presents a surprisingly close contest between these two Coffee Lake parts, despite their different market segments. The Intel Core i5-8279U takes the majority of head-to-head wins, but the Intel Core i5-8400T secures the most decisive victory.

In multi-core Cinebench workloads, the 8279U edges ahead by a narrow margin. The R15 multi-core test shows a score of 634 for the 8279U versus 633 for the 8400T, a delta of only -0.2%. The pattern repeats in R20, where the 8279U scores 2643 against 2638, and in R23, where it scores 6294 against 6282. These differences are effectively negligible, representing less than one percent separation across all three Cinebench versions.

Single-core Cinebench results are even closer. The R15 and R20 tests show identical scores of 89 and 372 respectively. The R23 single-core test gives a slight edge to the 8279U, 888 versus 886, a -0.2% delta. This suggests that for pure Cinebench workloads, the two processors are functionally interchangeable.

The real divergence appears in Geekbench. The 8400T wins the Geekbench multi-core test decisively with a score of 4011 against 3764, a 6.6% advantage. This is the largest margin recorded in any benchmark between the two. However, the 8279U counters with a strong Geekbench single-core result, scoring 1209 versus 1100, a 9% lead for the mobile part. This -9% delta represents the biggest single-score gap in the entire comparison.

The overall win tally favors the 8279U, which claims 5 wins against 3 for the 8400T. However, the average benchmark scores tell a slightly different story: the 8400T averages 2001 across all tests, while the 8279U averages 1987. The 8400T also holds a marginally better percentile ranking, sitting at the 45th percentile versus the 8279U's 44th percentile. These aggregate figures indicate that while the 8279U wins more individual tests, the 8400T's Geekbench multi-core advantage is large enough to lift its overall average above its rival.

Architecture Differences

Both processors share the Coffee Lake architecture and are built on Intel's 14 nm process node, but they diverge significantly in their physical configuration and intended deployment.

The 8400T is a desktop part with 6 physical cores and 6 threads, while the 8279U is a mobile processor with 4 cores and 8 threads thanks to Hyper-Threading. This core count difference explains the 8400T's Geekbench multi-core advantage: it has two additional physical cores to draw upon, even though the 8279U can process more threads per core.

Clock speeds favor the mobile chip. The 8279U runs at a 2.40 GHz base clock and boosts to 4.10 GHz, whereas the 8400T operates at a 1.70 GHz base clock with a 3.30 GHz boost. These figures are reflected in the Geekbench single-core results, where the 8279U's higher boost clock translates directly into a 9% advantage.

The 8400T uses the Intel Socket 1151 platform, while the 8279U is soldered to Intel BGA 1526, making it a non-upgradeable mobile solution. The desktop chip has a 35 W TDP, while the mobile part draws 28 W. Despite the lower TDP, the 8279U manages higher clock speeds, a result of its smaller 126 mm² die size and 2,300 million transistors, compared to the 8400T's 154 mm² die.

Cache configurations differ as well. The 8400T has 9 MB of shared L3 cache, while the 8279U has 6 MB shared L3. Both parts have 64 KB of L1 cache per core and 256 KB of L2 cache per core. The larger L3 cache on the desktop part provides more capacity for frequently accessed data.

Memory bandwidth also separates the two. The 8400T supports 42.7 GB/s of dual-channel DDR4 memory bandwidth, while the 8279U is limited to 34.1 GB/s. Both support DDR4 memory and dual-channel operation, but the desktop platform's higher bandwidth ceiling benefits memory-intensive workloads.

Integrated graphics differ notably. The 8400T carries UHD Graphics 630, while the 8279U features Iris Pro Plus 655, a more capable integrated GPU. Both provide Gen 3 PCIe with 16 lanes via the CPU.

The release timeline shows the 8400T arriving first, released on 2018-04-01, while the 8279U followed on 2019-04-02. Both are now end-of-life products with locked multipliers.

FAQ

Q: Which processor has more cores?

A: The Intel Core i5-8400T has 6 cores and 6 threads, while the Intel Core i5-8279U has 4 cores and 8 threads. The 8400T provides two additional physical cores, giving it an advantage in multi-threaded workloads like Geekbench multi-core, where it scored 4011 versus 3764, a 6.6% lead.

Q: Is the 8279U faster in single-core performance despite being a mobile chip?

A: Yes, the 8279U leads Geekbench single-core testing with a score of 1209, outperforming the 8400T's score of 1100, a 9% advantage. Its higher boost clock of 4.10 GHz, compared to the 8400T's 3.30 GHz, supports this result in better single-threaded performance.

A: The 8279U records slightly better Cinebench multi-core scores across all three versions. It scores 634 in R15, 2643 in R20, 6294 in R23, and 888 in R23, all slight edges over the 8400T's 633, 2638, 6282, and 886 respectively. The deltas are all -0.2%, meaning the difference is negligible in practical terms.

Q: What are the TDPs of the two processors?

A: The 8400T has a 35 W TDP, while the 8279U has a 28 W TDP. The mobile chip runs at lower power while achieving higher clock speeds, indicating a more power-efficient design for its intended laptop use.

Q: Do they use the same socket?

A: No, the 8400T uses Intel Socket 1151, while the 8279U uses Intel BGA 1526. The desktop chip is socketed and can theoretically be replaced, while the mobile chip is soldered to the board.

Q: Which processor has better integrated graphics?

A: The 8279U features Iris Pro Plus 655 graphics, which is a more capable integrated GPU than the 8400T's UHD Graphics 630, making the mobile chip better suited for light graphical tasks without a discrete GPU.

The Verdict

The data presents a nuanced choice. The Intel Core i5-8279U wins more individual benchmarks, taking 5 of the 8 head-to-head tests, and posts a decisive 9% lead in Geekbench single-core performance. Its higher boost clock of 4.10 GHz and 8 threads make it the stronger option for lightly threaded applications and tasks that benefit from thread-level parallelism.

However, the Intel Core i5-8400T counters with the largest win of any benchmark: its 6.6% advantage in Geekbench multi-core, driven by two additional physical cores. It also holds a higher average benchmark score of 2001 versus 1987 and a better percentile ranking at 45 versus 44.

For desktop users who prioritize multi-core throughput in applications like Geekbench, the 8400T's six physical cores provide a measurable benefit. For mobile users who need the best single-core performance and are constrained by a 28 W TDP, the 8279U is the stronger choice, despite its lower overall average score.

The Cinebench results are effectively a tie, with deltas of only -0.2% across all versions. This means that for rendering workloads, users should not expect a meaningful difference between the two.

The 8400T's larger 9 MB L3 cache and higher memory bandwidth of 42.7 GB/s give it an edge in cache-sensitive and memory-heavy workloads. The 8279U's smaller 6 MB L3 cache and 34.1 GB/s bandwidth are trade-offs for its compact 126 mm² die and mobile power envelope.

Neither chip is unlocked, and both are end-of-life products. The decision ultimately rests on platform and workload: desktop users with Socket 1151 motherboards and multi-core needs should pick the 8400T, while laptop buyers seeking single-core performance and a lower TDP should pick the 8279U.

The launch MSRP for the 8400T is $182, which is notably lower than the 8279U's launch MSRP of $320. This price difference aligns with the desktop part's lower cost per physical core ratio, though the 28 W TDP and higher clock speeds of the 8279U justify the mobile premium for portable use cases.

The 8279U's Geekbench single-core advantage of 9% is the most significant single-score gap in the comparison, making it the clear winner for emulation, legacy software, and single-threaded productivity tasks. The 8400T's Geekbench multi-core win of 6.6% makes it superior for compiling, video encoding, and 3D modeling workloads that scale across physical cores.

Overall benchmark results indicate a virtual tie in Cinebench, a slight advantage for the 8279U in overall win count, and a higher average score for the 8400T.

Specification Differences

The two processors differ in several key specification fields:

• Cores and Threads: 6 cores 6 threads on the 8400T versus 4 cores and 8 threads on the 8279U**
• Base Clock: 1700 MHz on the 8400T versus 2400 MHz on the 8279U with a boost clock of 4100 MHz against 3300 MHz respectively**
• TDP: 35 W for the 8400T versus 28 W for the 8279U
• Socket Type: Intel Socket 1151 for the 8279U versus Intel BGA 1526 for the 8279U with the 8400T uses the 1151 socket**
• Architecture Codename: Coffee Lake for the 8400T and Coffee Lake-U for the 8279U with the 8279U using the Coffee Lake-U codename**
• Transistors: 2300 million transistors for the 8279U versus no listed transistor count for the 8400T
• Die Size: 154 mm² for the 8400T versus 126 mm² for the 8279U
• L3 Cache: 9 MB shared for the 8400T versus 6 MB shared for the 8279U
• Memory Bandwidth: 42.7 GB/s for the 8400T versus 34.1 GB/s for the 8279U
• Integrated Graphics Model: UHD Graphics 630 for the 8400T versus Iris Pro Plus 655 for the 8279U with the 8400T having a different GPU model**
• Market Segment: Desktop for the 8400T versus Mobile for the 8279U
• Release Date: 2018-04-01 for the 8400T versus 2019-04-01 for the 8279U with the 8400T released earlier**
• Part Number: SR3X6 for the 8400T versus SREZ0 for the 8279U
• Percentile: 45th percentile for the 8400T versus 44th percentile for the 8279U with the 8400T holding a higher percentile**
• Average Benchmark Score: 2001 for the 8400T versus 1987 for the 8279U
• Memory Support: DDR4 for DDR4 is for DDR4 for both processors with DDR4 memory support**
• Process Node: 14 nm for both processors with the 14 nm process node for both processors with the 8279U using the 14 nm node for the 8279U process for the 8279U node for the 8279U process node for the 8279U node for the 8279U process**
• Foundry: Intel for both processors with Intel foundry for both processors with Intel as the foundry for both processors with Intel foundry for both processors with the 8279U using Intel foundry for the 8279U foundry for the 8279U foundry for the 8279U process node for the 8279U process node for the 8279U node for the 8279U**
• L1 Cache: 64 KB per core for the 8400T for the 8279U with 64 KB per core for the 8279U with 64 KB per core for the 8400T with 64 KB per core for the 8279U with 64 KB per core for the 8400T**
• L2 Cache: 256 KB per core for the 8400T with 256 KB per core for the 8279U with 256 KB per core for the 8400T with 256 KB per core for the 8279U with 256 KB per core for the 8400T**

Where Each One Wins| Feature or benchmark | Intel Core i5-8400T | Intel Core i5-8279U | Winner |

| Geekbench multi-core | 4011 | 3764 | 8400T (6.6%) |

| Cinebench R15 multi-core | 633 | 634 | 8279U (-0.2%)** |

| Cinebench R20 multi-core | 2638 | 2643 | 8279U (-0.2%)** |

| Cinebench R23 multi-core | 6282 | 6294 | 8279U (-0.2%)** |

| Geekbench single-core | 1100 | 1209 | 8279U (9%) |

| Cinebench R15 single-core | 89 | 89 | Tie |

| Cinebench R20 single-core | 372 | 372 | Tie |

| Cinebench R23 single-core | 886 | 888 | 8279U (-0.2%)** |

The 8400T wins in multi-core Geekbench, a result driven by its 6 physical cores, and holds an advantage in L3 cache size at 9 MB versus 6 MB, along with higher memory bandwidth of 42.7 GB/s versus 34.1 GB/s. Its average benchmark score of 2001 also sits above the 8279U's 1987.

The 8279U wins in single-core Geekbench with a 9% margin, wins five of the eight head-to-head tests, and achieves higher clock speeds with a 4.10 GHz boost. Its 28 W TDP makes it suitable for thinner mobile designs, and its Iris Pro Plus 655 integrated graphics provide a more capable GPU solution. The 8279U also has 8 threads versus 6, which benefits heavily threaded workloads that can exploit simultaneous multithreading, despite having fewer physical cores.

For rendering tasks measured by Cinebench, the two are effectively identical, with all deltas at -0.2% or 0%, meaning users should base their choice on other factors. For desktop builds with Socket 1151 and multi-core Geekbench workloads, the 8400T is the answer. For mobile systems with BGA 1526 and single-core performance priorities, the 8279U is the answer.