Intel Core i3-8121U vs Intel Core i7-8665UE Comparison

Head-to-Head Benchmarks

The recorded benchmark data shows a clean sweep for the Intel Core i7-8665UE across every single test in the database. There are no contests where the Intel Core i3-8121U comes out ahead. The i7-8665UE wins all six head-to-head comparisons, covering Cinebench R15, R20, and R23 in both single-core and multi-core workloads.

Looking at the multi-core results, the gap is remarkably consistent. In Cinebench R15 multi-core, the i3-8121U scores 366 while the i7-8665UE reaches 415, a difference of 11.8 percent. The same pattern appears in Cinebench R20 multi-core, where the i3-8121U records 1527 points and the i7-8665UE posts 1732 points, again an 11.8 percent advantage. Cinebench R23 multi-core follows with 3637 points for the i3-8121U and 4124 points for the i7-8665UE, matching the same 11.8 percent delta. This consistency suggests the performance gap is structural rather than workload-specific, likely tied to the difference in core and thread counts.

Single-core results tell a similar story, though with slightly larger percentage gaps. In Cinebench R15 single-core, the i3-8121U scores 51 while the i7-8665UE scores 58, a 12.1 percent lead. Cinebench R20 single-core shows 215 points for the i3-8121U versus 244 points for the i7-8665UE, an 11.9 percent difference. Cinebench R23 single-core rounds this out with 513 points for the i3-8121U and 582 points for the i7-8665UE, again an 11.9 percent margin. The fact that the i7-8665UE wins single-core tests by nearly the same margin as multi-core tests indicates that its advantage is not purely about having more cores, but also about higher per-thread performance.

The Geekbench results are only recorded for the i3-8121U, which scores 2215 in multi-core and 1149 in single-core. The database does not include Geekbench scores for the i7-8665UE, so no direct comparison is possible on that test. However, the Cinebench suite provides consistent evidence across three different renderer versions.

The overall average benchmark score in the database places the i3-8121U at 1209, while the i7-8665UE sits at 1193. This puts the i3-8121U slightly higher in aggregate averaging, even though it loses every head-to-head test. That apparent contradiction stems from how the averages are computed across different test suites, including Geekbench where only the i3-8121U has data. The percentile rankings are nearly identical: the i3-8121U lands in the 34th percentile of all CPUs, and the i7-8665UE in the 33rd percentile.

FAQ

Q: Which processor wins in multi-core rendering workloads?

A: The Intel Core i7-8665UE wins every multi-core Cinebench test. It scores 415 versus 366 in R15, 1732 versus 1527 in R20, and 4124 versus 3637 in R23. Each result shows an 11.8 percent advantage for the i7-8665UE.

Q: Does the i3-8121U have any benchmark where it outperforms the i7-8665UE?

A: No. The recorded head-to-head data includes six tests, and the i7-8665UE wins all six. The i3-8121U's only recorded wins are in tests where the i7-8665UE has no data, such as Geekbench, where the i3-8121U scores 2215 multi-core and 1149 single-core.

Q: How different are their average benchmark scores?

A: The i3-8121U has an average benchmark score of 1209, while the i7-8665UE averages 1193. This is a 16-point difference in favor of the i3-8121U, though this average includes Geekbench results that are not available for the i7-8665UE.

Q: Which processor has the higher single-core performance?

A: The i7-8665UE leads in all three single-core Cinebench tests: 58 versus 51 in R15, 244 versus 215 in R20, and 582 versus 513 in R23. The percentage gaps range from 11.9 to 12.1 percent.

Q: Are these processors in the same performance tier?

A: Yes. The i3-8121U sits in the 34th percentile of all CPUs, and the i7-8665UE sits in the 33rd percentile. Their nearest rivals also overlap in scoring range: the i3-8121U is matched with Intel Xeon D-1520, Intel Xeon E5645, Intel Xeon D-1527, and Intel Core i3-7300T, while the i7-8665UE matches with Intel Core i3-4170, AMD Athlon PRO 300U, AMD Opteron 3365, and AMD Opteron 6234.

Q: What is the launch MSRP of the i7-8665UE?

A: The launch MSRP is $409. The i3-8121U has no recorded launch MSRP in the database.

Architecture Differences

The two processors come from different Intel architecture families. The i3-8121U is built on Cannon Lake, while the i7-8665UE uses Whiskey Lake. These are not minor revisions of the same design; they represent separate approaches to mobile computing at the time of their release.

The manufacturing process differs substantially. The i3-8121U uses a 10 nm process node, while the i7-8665UE uses 14 nm. This is notable because the i3-8121U is one of the earlier Intel parts on 10 nm, and its die size is recorded at 70.52 mm². The i7-8665UE has no recorded die size in the database. Despite the smaller process node, the i3-8121U does not translate that into a performance advantage, as the benchmark results show.

Core and thread counts are another clear divider. The i3-8121U has 2 cores and 4 threads, while the i7-8665UE doubles that to 4 cores and 8 threads. This explains the consistent multi-core advantage for the i7-8665UE, though it does not fully explain the single-core lead, which is more about clock behavior and microarchitecture.

Cache hierarchies also differ. Both processors have 64 KB of L1 cache per core and 256 KB of L2 cache per core. The shared L3 cache, however, is 4 MB for the i3-8121U and 8 MB for the i7-8665UE. The larger shared cache on the i7-8665UE can hold more working set data, which may contribute to its performance in both single and multi-threaded scenarios.

The integrated graphics are different as well. The i3-8121U has no integrated graphics listed in the database. The i7-8665UE includes UHD Graphics 620, which gives it a built-in display output capability that the i3-8121U lacks in the recorded specifications.

Both processors support DDR4 memory in dual-channel configuration, with a memory bandwidth of 38.4 GB/s. However, the i7-8665UE also lists DDR3 support, while the i3-8121U only lists DDR4. Neither processor supports ECC memory. Both use PCIe Gen 3 with 16 lanes available from the CPU.

The sockets are different: the i3-8121U uses Intel BGA 1440, and the i7-8665UE uses Intel BGA 1528. This means they are not drop-in interchangeable on the same motherboard, which matters for system integrators choosing between them.

Specification Differences

The base clock rates show a striking difference. The i3-8121U has a base clock of 2.20 GHz, while the i7-8665UE lists a base clock of 1700.00. That figure for the i7-8665UE appears to be a recorded anomaly in the database, since its boost clock is 4.40 GHz. The i3-8121U boosts to 3.20 GHz. The boost clock difference is substantial: 4.40 GHz versus 3.20 GHz, a 1.20 GHz gap that helps explain the i7-8665UE's single-core wins.

Both processors have a TDP of 15 watts, which places them in the same thermal envelope for mobile designs. This makes the performance difference noteworthy, as the i7-8665UE delivers higher scores across all Cinebench tests while consuming the same rated power.

Memory support differs in scope. The i3-8121U supports DDR4 only. The i7-8665UE supports both DDR3 and DDR4. Both run dual-channel memory at 38.4 GB/s bandwidth.

The process node and die size are also differentiators. The i3-8121U is built on 10 nm with a die size of 70.52 mm². The i7-8665UE is built on 14 nm with no recorded die size. The i3-8121U's smaller process node does not yield a performance advantage in the recorded benchmarks.

The i3-8121U has no integrated graphics listed, while the i7-8665UE includes UHD Graphics 620. This is a functional difference for systems that rely on the CPU's built-in display output.

Both processors have locked multipliers, meaning overclocking is not supported. The i3-8121U has part number SRCVC, and the i7-8665UE has part number SRF9W.

The i7-8665UE has a launch MSRP of $409, while no launch MSRP is recorded for the i3-8121U. Both are marked as end-of-life production status.

The Verdict

The data points to one clear conclusion: the Intel Core i7-8665UE is the faster processor in every recorded head-to-head benchmark. It wins all six Cinebench tests, covering three different versions of the renderer and both single-core and multi-core workloads. The consistency of the 11.8 to 12.1 percent margins suggests a stable performance advantage across different software generations.

The i3-8121U does have a higher average benchmark score in the database, at 1209 versus 1193, but that figure is influenced by Geekbench results that are not recorded for the i7-8665UE. When comparing only the tests where both processors have data, the i7-8665UE leads without exception.

The i7-8665UE also offers more cores, more threads, double the L3 cache, a higher boost clock, and integrated graphics. The i3-8121U counters with a smaller process node and a lower base clock, but neither translates into a benchmark victory.

For mobile system design, the 15-watt TDP on both parts means the i7-8665UE delivers its performance advantage within the same thermal budget. That is a meaningful result for thin-and-light laptops or embedded systems where cooling is constrained.

Where Each One Wins

The i7-8665UE wins in every scenario covered by the head-to-head benchmarks. Multi-threaded rendering favors it strongly, with an 11.8 percent lead across R15, R20, and R23. Single-threaded workloads also favor it, with margins between 11.9 and 12.1 percent. Any application that relies on Cinebench-style rendering, 3D modeling, or CPU-bound video encoding would see a measurable improvement with the i7-8665UE.

The i3-8121U's only recorded wins come in tests where the i7-8665UE has no data. In Geekbench multi-core, the i3-8121U scores 2215, and in Geekbench single-core, it scores 1149. These are standalone figures, not comparisons, so they do not establish superiority over the i7-8665UE. They do show that the i3-8121U is not a weak performer on its own terms, sitting in the 34th percentile of all CPUs.

The i3-8121U's smaller 10 nm process node and 70.52 mm² die size suggest it may have advantages in manufacturing density or power characteristics at the component level, but the database does not record any thermal or efficiency tests to confirm this. The 15-watt TDP on both processors means no power advantage is recorded either.

For buyers or integrators choosing between these two, the benchmark data is unambiguous: the i7-8665UE is the stronger choice for CPU performance across the board. The i3-8121U remains a capable dual-core part for basic workloads, but it cannot match the i7-8665UE in any test where both have recorded scores.