AMD Ryzen 5 8640U vs Intel Core i9-11900K Comparison

The Intel Core i9-11900K and AMD Ryzen 5 8640U represent two very different philosophies: a high-power desktop flagship from 2021 versus a modern, efficient mobile processor. The data shows a decisive overall victory for the Intel part, which wins 14 of the 17 head-to-head benchmarks, but the AMD chip is not without its own merits. The average benchmark scores are remarkably close—26,639 for the Intel versus 26,462 for the AMD—placing the i9-11900K at the 79th percentile and the Ryzen 5 8640U at the 78th percentile of all CPUs, yet the nature of their wins is entirely different.

Head-to-Head Benchmarks

The most striking disparity appears in multi-threaded workloads, where the Intel Core i9-11900K’s extra two cores and four threads translate into massive leads. In Cinebench R23 multi-core, the Intel scores 21,168 against the AMD’s 10,433, a delta of 102.9%—meaning the Intel part is more than twice as fast. This pattern repeats in Geekbench multi-core, where the Intel’s 13,550 exceeds the AMD’s 8,185 by 65.5%. Even in Cinebench R15 multi-core, the gap is a substantial 28.3% (2,133 vs 1,663). For anyone running heavy parallel workloads like video rendering or 3D simulation, the Intel desktop chip is in a different league.

Single-thread performance tells a more nuanced story. The Intel i9-11900K wins Cinebench R15 single-core by 17.2% (300 vs 256) and Cinebench R23 single-core by a massive 81% (2,988 vs 1,651). However, in PassMark’s single-thread test, the AMD Ryzen 5 8640U actually takes the win, scoring 3,534 versus the Intel’s 3,511—a slim 0.7% margin. Geekbench single-core is also close, with the Intel leading by just 6.7% (2,273 vs 2,131). This suggests that while the Intel part has superior peak single-core performance in some tests, the AMD’s Zen 4 architecture is highly competitive in others, especially in older or differently-optimized benchmarks.

The Intel CPU dominates nearly every other category. In PassMark data compression, it scores 330,836 versus 230,080, a 43.8% advantage. Integer math shows a 31.2% lead (89,279 vs 68,051), and floating-point math a 31% lead (52,841 vs 40,330). Extended instructions (like AVX-512) favor the Intel part by 41.9% (23,406 vs 16,500). Even in memory-sensitive tasks like random string sorting, the Intel is 35.2% ahead (37,942 vs 28,066). The only other AMD win besides the PassMark single-thread test is in the niche PassMark find prime numbers test, where the AMD scores 69 against the Intel’s 68, a 1.4% difference that is practically negligible.

FAQ

Q: Which CPU has the higher average benchmark score?

A: The Intel Core i9-11900K has a slightly higher average benchmark score of 26,639, compared to the AMD Ryzen 5 8640U’s 26,462. This difference is less than 1%, placing both chips in the same performance tier overall.

Q: Is the AMD Ryzen 5 8640U competitive in any benchmark?

A: Yes, the AMD chip wins the PassMark single-thread test (3,534 vs 3,511) and the PassMark find prime numbers test (69 vs 68). It also comes very close in Geekbench single-core, trailing by only 6.7%.

Q: How large is the multi-core performance gap?

A: The gap is enormous. In Cinebench R23 multi-core, the Intel i9-11900K is 102.9% faster than the AMD Ryzen 5 8640U (21,168 vs 10,433). In Geekbench multi-core, the Intel leads by 65.5%.

Q: What are the power consumption differences?

A: The Intel Core i9-11900K has a TDP of 125 watts, while the AMD Ryzen 5 8640U has a TDP of 28 watts. This indicates the Intel chip is designed for high-performance desktop use with substantial cooling, while the AMD is a low-power mobile part.

Q: Which processor has a higher boost clock?

A: The Intel Core i9-11900K has a higher boost clock of 5.30 GHz, compared to the AMD Ryzen 5 8640U’s 4.90 GHz. Both have the same base clock of 3.50 GHz.

Q: Do both CPUs support the same memory type?

A: No. The Intel Core i9-11900K supports DDR4 memory with a bandwidth of 51.2 GB/s, while the AMD Ryzen 5 8640U supports DDR5 memory with a bandwidth of 89.6 GB/s.

Architecture Differences

The architectural divide between these two chips is generational and philosophical. The Intel Core i9-11900K is built on Intel’s 14 nm process node, a mature but power-hungry design from the Rocket Lake family. It features 8 cores and 16 threads, with a die size of 276 mm². In contrast, the AMD Ryzen 5 8640U is a modern marvel built on TSMC’s 4 nm process, packing 6 cores and 12 threads into a much smaller 178 mm² die. The AMD chip also integrates 25,000 million transistors, a figure the Intel part does not disclose.

Cache layouts also differ significantly. The Intel i9-11900K uses 80 KB of L1 cache per core and 512 KB of L2 per core, but only 16 MB of shared L3 cache. The AMD Ryzen 5 8640U reduces L1 to 64 KB per core but doubles L2 to 1 MB per core, while also featuring 16 MB of shared L3 cache. This larger L2 cache on the AMD part helps offset its lower core count in some workloads.

The integrated graphics are another key differentiator. The Intel chip includes UHD Graphics 750, while the AMD Ryzen 5 8640U features the Radeon 760M. While neither is designed for high-end gaming, the AMD’s Radeon 760M is a more modern architecture. The Intel chip has an unlocked multiplier, making it overclockable, while the AMD part is locked. Finally, the Intel i9-11900K is end-of-life, while the AMD Ryzen 5 8640U is still an active product.

Specification Differences

The most obvious specification difference lies in the core and thread counts: the Intel i9-11900K has 8 cores and 16 threads, while the AMD Ryzen 5 8640U has 6 cores and 12 threads. Boost clocks differ, with the Intel reaching 5.30 GHz versus the AMD’s 4.90 GHz, though base clocks are identical at 3.50 GHz. The TDP is a stark contrast—125 watts for the Intel desktop part versus 28 watts for the AMD mobile processor.

Memory support diverges completely: the Intel uses DDR4, while the AMD uses DDR5, and the memory bandwidth reflects this, with the AMD offering 89.6 GB/s versus the Intel’s 51.2 GB/s. The sockets are incompatible, with the Intel using Intel Socket 1200 and the AMD using AMD Socket FP8. Process technology also differs, with the Intel on 14 nm and the AMD on 4 nm. The Intel chip has a launch MSRP of $539, while the AMD chip has no listed launch MSRP. The Intel is a desktop part, while the AMD is a mobile part.

Where Each One Wins

The Intel Core i9-11900K is the clear winner for compute-heavy, multi-threaded desktop tasks. Its 102.9% lead in Cinebench R23 multi-core and 65.5% lead in Geekbench multi-core make it the obvious choice for video editing, 3D rendering, software compilation, and any workload that scales with core count. Its 43.8% advantage in data compression and 31.2% lead in integer math also make it suitable for database work and scientific computing. It is also a strong performer in single-core tasks, leading by 81% in Cinebench R23 single-core, though the AMD edges it out in PassMark’s single-thread test.

The AMD Ryzen 5 8640U wins in efficiency and portability. Its 28-watt TDP makes it suitable for thin-and-light laptops where battery life and thermal management are critical. The data shows it is no slouch in single-thread performance, winning the PassMark single-thread test and nearly tying Geekbench single-core. Its higher memory bandwidth (89.6 GB/s) with DDR5 support could give it an edge in memory-bandwidth-sensitive applications. The AMD chip is also the only one of the two with an active production status, making it a viable choice for current system builds.

The Verdict

The data is unambiguous: for raw performance, the Intel Core i9-11900K wins 14 of 17 benchmarks, often by overwhelming margins. If your priority is maximum multi-threaded throughput and you have the power budget and cooling for a 125-watt desktop processor, the Intel part is the one to choose. Its average benchmark score of 26,639 is higher, and its percentile ranking of 79th versus the AMD’s 78th confirms its slight edge.

However, the AMD Ryzen 5 8640U is not a lesser product; it is a different one. Its 28-watt TDP makes it ideal for mobile devices where the Intel’s 125-watt requirement is simply not an option. The AMD chip’s wins in PassMark single-thread and find prime numbers, along with its competitive Geekbench single-core score, show that Zen 4 has closed the single-core gap in certain tests. For a user building a portable laptop, the AMD Ryzen 5 8640U is the only practical choice between these two. For a desktop user who needs the highest possible multi-core performance, the Intel Core i9-11900K is the definitive winner, despite its older architecture and higher power draw.