Intel Core i3-8300 vs Intel Core i7-8665U Comparison

Where Each One Wins

The Intel Core i3-8300 wins every recorded benchmark in this comparison. Across six Cinebench tests, spanning R15, R20, and R23 in both single-core and multi-core workloads, the desktop part takes a clean 6-0 sweep. The margins are narrow but consistent, ranging from 2.7% to 3.6%.

The i3-8300's strongest advantage appears in Cinebench R20 single-core, where it leads by 3.6% (320 vs 309). Its smallest edge is in R15 single-core, at 2.7% (76 vs 74). All multi-core tests show a 3.4% gap, which suggests the i3-8300 maintains its lead whether the workload scales across all cores or stays on a single thread.

The Intel Core i7-8665U, by contrast, does not win a single test. Its best result is in R15 multi-core, where it scores 527 against 545. This is not a performance failure; it is simply a slower chip in every measured scenario. The data indicates the i7-8665U trails by roughly 3% across the board, which is a small but repeatable deficit.

For use-case planning, the split is straightforward. The i3-8300 is the pick for any workload measured here, including rendering and CPU-bound tasks that Cinebench represents. The i7-8665U is not competitive in these tests, though its mobile positioning means it may serve other priorities such as power efficiency, which the benchmark scores do not capture.

Architecture Differences

Both processors share a 14 nm process node from Intel, and both use four physical cores. The first major divergence is threading: the i3-8300 runs 4 threads, while the i7-8665U runs 8 threads via Hyper-Threading. Despite having twice the thread count, the i7-8665U still loses all multi-core tests, which points to the desktop part's higher sustained clocks.

Base clocks differ substantially. The i3-8300 runs at 3.70 GHz, while the i7-8665U has a 1900.00 MHz base. The mobile chip can boost to 4.80 GHz, but the i3-8300 has no boost clock listed in the database, meaning its 3.70 GHz is effectively its operating ceiling. The i7-8665U's boost capability narrows the gap but does not close it.

Cache layouts are identical in structure: 64 KB L1 per core, 256 KB L2 per core, and 8 MB shared L3. The die size differs, with the i3-8300 at 126 mm² while the i7-8665U has no recorded die size. Both support dual-channel memory with 38.4 GB/s bandwidth, but the i3-8300 only accepts DDR4, while the i7-8665U accepts both DDR3 and DDR4.

Integrated graphics differ: the i3-8300 has UHD Graphics 630, and the i7-8665U has UHD Graphics 620. ECC memory support is exclusive to the i3-8300; the i7-8665U does not support it. Both use PCIe Gen 3 with 16 lanes from the CPU. The sockets are incompatible: the i3-8300 uses Intel Socket 1151, and the i7-8665U uses Intel BGA 1528.

Power envelopes are a major separator. The i3-8300 has a 62 W TDP, while the i7-8665U is rated at 15 W. This explains the clock behavior: the desktop chip can hold a high base clock, while the mobile chip relies on boost to reach competitive speeds within a much lower power limit.

The Verdict

The data points to one clear conclusion: the Intel Core i3-8300 is the faster processor in every benchmark recorded. If the choice is purely about Cinebench performance, the i3-8300 wins without qualification.

The i7-8665U's advantages are not visible in the benchmark scores. It offers 8 threads, a higher boost clock, and a dramatically lower 15 W TDP, but none of those translate into a single test victory. Its nearest rivals in the database include the Intel Pentium Gold G7400E and the Core i5-4670S, with average scores of 1524 and 1526, respectively. The i3-8300 sits near the AMD Ryzen 3 1300X and the Core i5-6600T, with average scores of 1562 and 1563.

For a desktop system where sustained performance matters, the i3-8300 is the obvious choice. For a mobile or power-constrained design, the i7-8665U is the only one that fits, given its BGA socket and 15 W envelope. The benchmark data cannot recommend the i7-8665U on performance grounds; it wins no measured test.

The percentile ranking confirms the closeness: the i3-8300 sits at the 39th percentile of all CPUs, and the i7-8665U at the 38th. The overall average benchmark scores are 1564 for the i3-8300 and 1513 for the i7-8665U, a 3.4% difference that mirrors the head-to-head results.

FAQ

Q: Which CPU has better multi-core performance?

A: The i3-8300 wins all three multi-core tests: R15 by 3.4% (545 vs 527), R20 by 3.4% (2271 vs 2197), and R23 by 3.4% (5408 vs 5232).

Q: Does the i7-8665U's 8 threads help it win any benchmark?

A: No. Despite having 8 threads against the i3-8300's 4 threads, the i7-8665U loses every multi-core test by 3.4%.

Q: What is the single-core performance difference?

A: The i3-8300 leads in R15 single-core by 2.7% (76 vs 74), in R20 by 3.6% (320 vs 309), and in R23 by 3.4% (763 vs 738).

Q: Are the cache sizes the same?

A: Yes. Both have 64 KB L1 per core, 256 KB L2 per core, and 8 MB shared L3.

Q: Which processor supports ECC memory?

A: Only the i3-8300 supports ECC memory. The i7-8665U does not list ECC support.

Q: Why is the i7-8665U's base clock so much lower?

A: The i7-8665U has a 1900.00 MHz base clock and a 4.80 GHz boost clock, with a 15 W TDP. The i3-8300 runs at 3.70 GHz with no boost clock and a 62 W TDP. The lower power envelope forces the mobile chip to rely on boosting.

Head-to-Head Benchmarks

The cleanest way to read this matchup is through the six recorded Cinebench tests. In R15 multi-core, the i3-8300 scores 545 against 527, a 3.4% lead. In R15 single-core, it scores 76 against 74, a 2.7% lead. The R20 tests show a similar pattern: 2271 vs 2197 in multi-core (3.4%) and 320 vs 309 in single-core (3.6%). R23 rounds out the sweep: 5408 vs 5232 in multi-core (3.4%) and 763 vs 738 in single-core (3.4%).

The largest margin is the 3.6% in R20 single-core, which is also the only test where the gap exceeds 3.4%. The smallest margin is the 2.7% in R15 single-core. The consistency of the 3.4% figure across four of six tests suggests a stable performance gap that does not expand or contract based on workload type.

The i7-8665U's best relative performance is in R15 single-core, where it trails by only 2.7%. Its worst is in R20 single-core, where it trails by 3.6%. The i3-8300's average benchmark score is 1564, while the i7-8665U's is 1513. The nearest rivals for the i3-8300 include the Core i5-6600T at 1563 (0% delta) and the Ryzen 3 1300X at 1562 (0.1% delta). For the i7-8665U, the nearest rivals include the Pentium Gold G7400E at 1524 (-0.7%) and the Core i5-4670S at 1526 (-0.9%).

Specification Differences

The two processors differ on several recorded specifications. The i3-8300 has 4 threads; the i7-8665U has 8 threads. Base clocks are 3.70 GHz vs 1900.00 MHz, and only the i7-8665U lists a boost clock at 4.80 GHz. TDPs are 62 W vs 15 W. Sockets are Intel Socket 1151 vs Intel BGA 1528.

Architecture names differ: Coffee Lake for the i3-8300, Whiskey Lake for the i7-8665U. Memory support is DDR4-only for the i3-8300, while the i7-8665U accepts DDR3 and DDR4. ECC memory is supported by the i3-8300 but not the i7-8665U. Integrated graphics are UHD Graphics 630 vs UHD Graphics 620.

Release dates differ: the i3-8300 launched on 2018-02-13, and the i7-8665U on 2018-09-30. The launch MSRP for the i3-8300 was $138, and for the i7-8665U it was $409. The die size is recorded only for the i3-8300 at 126 mm². Both use 14 nm process nodes, dual-channel memory, 38.4 GB/s bandwidth, and PCIe Gen 3 with 16 lanes. Both have the same cache hierarchy: 64 KB L1 per core, 256 KB L2 per core, and 8 MB shared L3. Neither has an unlocked multiplier, and both are end-of-life products.