CPU Comparison

The Intel Core i5-8400 and Intel Atom x7809C represent two very different Intel design philosophies, yet their benchmark profiles are surprisingly close in overall average score. The data shows the Atom x7809C, a mobile part with a 25 W TDP, edges out the desktop i5-8400 in raw multi-threaded compute, while the i5-8400 counterattacks decisively in single-threaded and specialized workloads. This is not a simple victory lap for either chip; it is a nuanced split that rewards a careful look at the specific task at hand.

Head-to-Head Benchmarks

The most striking headline is the Atom x7809C’s consistent, if narrow, lead across the entire Cinebench suite. In Cinebench R15 multicore, the Atom scores 805 against the i5-8400’s 790, a 1.9% margin. That pattern repeats in R20 multicore (3358 vs 3295, also 1.9%) and R23 multicore (7997 vs 7847, again 1.9%). Even the single-core Cinebench tests tilt toward the Atom, with R20 single-core showing a 2.1% advantage (474 vs 464) and R23 single-core a 1.9% edge (1129 vs 1107). The consistency is remarkable: across six Cinebench runs, the Atom never trails by more than 2.1% and wins every one. This suggests the Atom’s Gracemont cores, despite a lower 2.00 GHz base clock, deliver comparable per-thread performance to the i5-8400’s Coffee Lake cores in these rendering workloads.

The PassMark suite, however, tells a more polarized story. The i5-8400 dominates in several specific tests. Its PassMark single-thread score of 2371 is a massive 62.2% higher than the Atom’s 1462, a gap that dwarfs the Cinebench single-core margins. The i5-8400 also crushes the Atom in extended instructions (11543 vs 5509, a 109.5% lead) and floating-point math (22006 vs 17856, 23.2% ahead). In data compression, the i5-8400 posts 129951 versus 111525, a 16.5% win. These are not small edges; they indicate architectural strengths in branch prediction, SIMD execution, and FPU throughput.

Conversely, the Atom x7809C wins the integer math test decisively, scoring 28946 against the i5-8400’s 25573, an 11.7% advantage. Its most dramatic victory is in data encryption, where it posts 7832 versus 2824, a 63.9% margin that is the largest single delta in the entire comparison. The Atom also takes the PassMark multithread test (9409 vs 9225, 2% ahead) and physics (686 vs 635, 7.4% ahead). The i5-8400 counters with narrow wins in find prime numbers (37 vs 29, 27.6%) and random string sorting (15952 vs 15728, 1.4%). Overall, the Atom wins 10 of 17 head-to-head benchmarks, but the i5-8400’s wins are often by larger margins, particularly in single-thread and compression tasks.

FAQ

Q: Which CPU has the higher average benchmark score?

A: The i5-8400 holds a slightly higher average benchmark score of 12765, compared to the Atom x7809C’s 12607. This places the i5-8400 in the 68th percentile of all CPUs, while the Atom sits in the 67th percentile.

Q: How does the Atom x7809C perform in encryption workloads relative to the i5-8400?

A: The data shows a massive advantage for the Atom. In the PassMark data encryption test, the Atom scores 7832, which is 63.9% higher than the i5-8400’s 2824. This is the largest performance delta between the two processors in any benchmark.

Q: Is the i5-8400 better for single-threaded tasks?

A: It depends on the benchmark. The i5-8400 wins the PassMark single-thread test by 62.2% (2371 vs 1462), but the Atom actually wins all three Cinebench single-core tests (R15, R20, R23) by margins of 1.8% to 2.1%. The PassMark test shows a clear i5-8400 advantage; Cinebench shows a narrow Atom edge.

Q: What are the nearest rivals for each CPU based on average score?

A: For the i5-8400, the nearest rivals include the Intel Xeon Gold 6348 (0.2% higher score) and the AMD Ryzen Threadripper 3990X (0.2% lower). For the Atom x7809C, the Intel Core i3-1215U is the closest match with a 0% delta, followed by the Intel Core i5-1230U at 0.4% higher.

Q: Which CPU has a higher core count?

A: The Atom x7809C has 8 cores and 8 threads, while the i5-8400 has 6 cores and 6 threads. The Atom also has a larger L1 cache per core (96 KB vs 64 KB) and a larger L2 cache per module (2 MB vs 256 KB per core), though the i5-8400 has more L3 cache (9 MB shared vs 6 MB shared).

Q: How do the TDPs compare?

A: The Atom x7809C has a TDP of 25 W, which is significantly lower than the i5-8400’s 65 W. This makes the Atom a more power-efficient part, particularly relevant for its mobile market segment.

The Verdict

The data points to a surprising conclusion: the Intel Atom x7809C is the better all-around performer in rendering and multi-threaded compute, despite being a mobile chip with a 25 W TDP. Its wins in every Cinebench test and in PassMark multithread, physics, integer math, and encryption give it a 10-7 win count in head-to-head benchmarks. The i5-8400, however, is the clear winner for single-threaded desktop applications that rely on PassMark’s metric, and it has a massive edge in extended instruction sets and floating-point math. For users prioritizing raw single-thread speed as measured by PassMark, the i5-8400 is the choice. For anyone running mixed workloads or heavily threaded rendering, the Atom x7809C offers comparable or better performance with far lower power consumption. The i5-8400’s higher average score (12765 vs 12607) is marginal and driven by its strong single-thread and compression results, but the Atom’s consistency across a wider range of tests makes it the more versatile processor in this comparison.

Specification Differences

The two CPUs diverge on nearly every fundamental specification. The i5-8400 has 6 cores and 6 threads, while the Atom x7809C has 8 cores and 8 threads. Clock speeds differ: the i5-8400 starts at 2.80 GHz and boosts to 4.00 GHz, whereas the Atom starts at 2.00 GHz and boosts to 3.60 GHz. The TDP gap is substantial, with the i5-8400 rated at 65 W against the Atom’s 25 W. They use different sockets: the i5-8400 fits Intel Socket 1151, while the Atom uses Intel BGA 1264. Memory support also differs, with the i5-8400 supporting only DDR4 in dual-channel mode (42.7 GB/s bandwidth), while the Atom supports both DDR4 and DDR5 but only in single-channel mode (38.4 GB/s). PCIe lane counts differ as well: the i5-8400 has 16 Gen 3 lanes, while the Atom has 9 Gen 3 lanes. The i5-8400 includes integrated UHD Graphics 630, while the Atom has no integrated graphics. Production status and release dates also contrast: the i5-8400 is end-of-life, released in October 2017, while the Atom is active, released in April 2024.

Architecture Differences

Architecturally, these are products from different Intel eras and design families. The i5-8400 uses the Coffee Lake architecture on a 14 nm process, with a die size of 154 mm². It is a desktop part from the Core i5 generation, featuring a traditional big-core design with a shared 9 MB L3 cache. The Atom x7809C, in contrast, uses the Amston Lake architecture on a 10 nm process, belonging to the Atom (Gracemont) generation. It is a mobile part with a modular cache design: 96 KB of L1 per core, 2 MB of L2 per module, and a smaller 6 MB shared L3 cache. The Atom’s process node is smaller, which helps explain its lower 25 W TDP despite having more cores. The i5-8400’s larger L3 cache (9 MB vs 6 MB) may contribute to its wins in data compression and single-thread PassMark tests, while the Atom’s newer 10 nm process and Gracemont cores appear to handle encryption and integer math more efficiently. Neither chip supports ECC memory, and both lack an unlocked multiplier. The i5-8400’s part number is SLAPL; the Atom’s is SRNEN.

Where Each One Wins

The Intel Core i5-8400 claims victory in workloads that stress single-thread performance and specific instruction paths. Its 62.2% lead in PassMark single-thread makes it the preferred choice for legacy desktop applications that rely heavily on one core. It is also the stronger option for data compression tasks, where its 16.5% advantage in that PassMark test is notable. The i5-8400’s dominance in extended instructions (109.5% lead) and floating-point math (23.2% lead) suggests it is better suited for scientific computing, 3D rendering that uses FPU-heavy paths, and software that leverages advanced SIMD instructions. Its larger 9 MB L3 cache and 16 PCIe lanes make it a more capable desktop platform for discrete GPUs and memory-hungry workloads.

The Intel Atom x7809C wins in power-sensitive and multi-threaded scenarios. Its 25 W TDP makes it the obvious choice for compact or fanless systems where thermal headroom is tight. Its wins in all Cinebench multicore tests (by ~1.9%) indicate it can handle video encoding and 3D rendering at a level matching the i5-8400, but with far less power draw. The Atom’s massive 63.9% lead in data encryption is a standout, pointing to hardware-accelerated cryptography or more efficient integer operations in its Gracemont cores. Its 11.7% win in integer math and 7.4% win in PassMark physics further cement its advantage in general compute and simulation tasks. With 8 cores and support for DDR5 memory, the Atom is better positioned for modern, threaded mobile workloads, even though its single-channel memory bus (38.4 GB/s) is a theoretical bottleneck. For users prioritizing energy efficiency and multi-threaded throughput, the Atom x7809C is the data-backed winner.