Intel Core i3-8121U vs Intel Core i5-2400 Comparison

FAQ

Q: Which processor has more physical cores?

A: The Intel Core i5-2400 has 4 physical cores, while the Intel Core i3-8121U has only 2 physical cores. Both processors support 4 threads total, meaning the i3-8121U uses hyper-threading to reach 4 threads, while the i5-2400 achieves 4 threads with its 4 physical cores.

Q: How does the power consumption differ between these two CPUs?

A: The Intel Core i3-8121U has a TDP of 15 watts, making it a low-power mobile part. The Intel Core i5-2400 has a TDP of 95 watts, which is more than six times higher, reflecting its desktop-oriented design and older manufacturing process.

Q: What manufacturing processes are used in each processor?

A: The Intel Core i3-8121U is built on Intel's 10 nm process node with a die size of 70.52 mm². The Intel Core i5-2400 uses the older 32 nm process node with a much larger die size of 216 mm² and 1,160 million transistors.

Q: Which CPU has a higher single-core performance in Geekbench?

A: The Intel Core i3-8121U scores 1149 in Geekbench single-core, compared to 666 for the Intel Core i5-2400. This gives the i3-8121U a 72.5% advantage in that specific test.

Q: What memory types do these processors support?

A: The Intel Core i3-8121U supports DDR4 memory with dual-channel configuration and a memory bandwidth of 38.4 GB/s. The Intel Core i5-2400 supports DDR3 memory with dual-channel configuration, though its memory bandwidth figure is not recorded in the database.

Q: Are both processors still in production?

A: No, both processors are marked as end-of-life in the database. The Intel Core i3-8121U was released on 2018-05-04, while the Intel Core i5-2400 was released on 2011-01-08.

Where Each One Wins

The head-to-head benchmark data shows a clean sweep: the Intel Core i3-8121U wins all 7 recorded comparisons against the Intel Core i5-2400. There are zero wins for the older desktop chip in the database. However, the magnitude of the victories varies significantly by workload type.

The most dramatic gap appears in Geekbench single-core, where the i3-8121U scores 1149 versus 666 for the i5-2400, a 72.5% advantage. This reflects the enormous generational leap in per-core efficiency between the two architectures. In contrast, the multicore tests show much narrower margins. The Cinebench R23 multicore result gives the i3-8121U a score of 3637 against 3272, a 11.2% lead, despite the i5-2400 having double the physical core count.

For users running lightly threaded applications, such as web browsing, office productivity, or older games that rely on single-core speed, the i3-8121U is decisively faster. The benchmark results indicate that the newer 10 nm process and higher boost clock of 3.20 GHz on the i3-8121U, compared to 3.40 GHz on the i5-2400, deliver substantially better per-thread performance. The data shows the i3-8121U also wins in threaded workloads like video encoding or 3D rendering, but by a much smaller margin, meaning the i5-2400's four physical cores partially compensate for its architectural age.

Architecture Differences

The Intel Core i3-8121U belongs to the Cannon Lake architecture, codenamed Cannon Lake, and is part of the Core i3 generation listed as Kaby Lake-U Refresh. It is built on Intel's 10 nm process node, which represents a significant manufacturing advancement over the 32 nm node used by the Intel Core i5-2400. The i5-2400 is based on the Sandy Bridge architecture, codenamed Sandy Bridge, from the Core i5 generation. This architectural gap spans roughly seven years of processor design evolution.

The i3-8121U has a die size of 70.52 mm², while the i5-2400 has a much larger die at 216 mm². The older chip packs 1,160 million transistors, whereas the transistor count for the i3-8121U is not recorded in the database. Despite the smaller die, the newer processor achieves higher performance due to the denser 10 nm process.

Cache hierarchies differ as well. Both processors have 64 KB of L1 cache per core and 256 KB of L2 cache per core. However, the L3 cache differs: the i3-8121U has 4 MB shared L3, while the i5-2400 has 6 MB shared L3. The older chip benefits from a larger last-level cache, though the newer architecture's efficiency compensates.

Both CPUs support PCIe Gen 3 with 16 lanes (CPU only). The i3-8121U lacks integrated graphics in the database, while the i5-2400 includes Intel HD 2000 integrated graphics. Neither processor supports ECC memory. The i3-8121U is a mobile part with a BGA 1440 socket, while the i5-2400 is a desktop part using Intel Socket 1155.

Specification Differences

The core and thread counts differ: the i3-8121U has 2 cores and 4 threads, while the i5-2400 has 4 cores and 4 threads. Base clock speeds show the i5-2400 at 3.10 GHz versus the i3-8121U at 2.20 GHz. Boost clocks are closer: 3.40 GHz for the i5-2400 and 3.20 GHz for the i3-8121U. The TDP difference is substantial: 15 watts for the mobile chip versus 95 watts for the desktop chip.

Memory support separates the two: the i3-8121U uses DDR4 with a recorded bandwidth of 38.4 GB/s, while the i5-2400 uses DDR3 with no bandwidth figure recorded. Both use dual-channel memory buses. The sockets are completely different: BGA 1440 for the i3-8121U and Socket 1155 for the i5-2400.

The release dates show a seven-year gap: the i5-2400 launched on 2011-01-08, and the i3-8121U on 2018-05-04. Part numbers are SRCVC for the i3-8121U and SR00Q for the i5-2400. Neither processor has an unlocked multiplier. The market segments differ: mobile for the i3-8121U and desktop for the i5-2400. The i5-2400 includes integrated graphics (Intel HD 2000), while the i3-8121U does not have a listed integrated graphics unit.

Head-to-Head Benchmarks

The database records seven head-to-head benchmark comparisons, and the Intel Core i3-8121U wins each one. The largest margin comes in Geekbench single-core, where the i3-8121U scores 1149 against 666 for the i5-2400, a 72.5% delta. This is the standout result in the dataset, showing that the newer architecture delivers nearly double the single-thread performance of the seven-year-old Sandy Bridge design.

In Cinebench R15 multicore, the i3-8121U scores 366 versus 329 for the i5-2400, a 11.2% advantage. The Cinebench R20 multicore test shows a similar pattern: 1527 for the i3-8121U against 1374 for the i5-2400, a 11.1% lead. The Cinebench R23 multicore result repeats the trend: 3637 versus 3272, again an 11.2% delta. These consistent margins across three generations of Cinebench indicate that the i3-8121U's two cores with hyper-threading outperform the i5-2400's four physical cores by roughly the same proportion in multi-threaded rendering workloads.

Single-core Cinebench results follow the expected pattern. In Cinebench R20 single-core, the i3-8121U scores 215 against 194 for the i5-2400, a 10.8% lead. Cinebench R23 single-core gives the i3-8121U a score of 513 versus 462, an 11% advantage. These margins are much smaller than the Geekbench single-core gap, suggesting that the Geekbench test is more sensitive to architectural improvements like instruction set extensions or memory latency.

Geekbench multicore shows the i3-8121U at 2215 versus 2011 for the i5-2400, a 10.1% lead. This is the narrowest margin in the entire dataset, highlighting that the i5-2400's additional physical cores help close the gap in general-purpose multithreaded tasks. The i3-8121U does not have a Cinebench R15 single-core score recorded for comparison, but the available data shows a consistent pattern of victory across all recorded tests.

Overall, the average benchmark score for the i3-8121U is 1209, while the i5-2400 averages 1187. The i3-8121U sits at the 34th percentile of all CPUs in the database, and the i5-2400 sits at the 33rd percentile. The nearest rivals for the i3-8121U include the Intel Xeon D-1520 with an identical average score, and the Intel Core i3-7300T with a score of 1211, which is 0.1% lower. The i5-2400's nearest rivals include the Intel Core i5-4460T at 1190, 0.2% lower, and the Intel Core i3-4170 at 1193, 0.5% lower. The benchmark results indicate that while the i3-8121U wins every direct comparison, both processors belong to the same performance tier in the overall database ranking.