Intel Core i9-11900KB vs Intel Core i9-9900X Comparison

Head-to-Head Benchmarks

The benchmark data presents a consistent picture across all six recorded Cinebench tests: the Intel Core i9-11900KB wins every single matchup against the Intel Core i9-9900X. The margins are narrow but uniform, ranging from 5.0% to 5.2% depending on the test. In Cinebench R15 multicore, the i9-11900KB scores 1946 against 1851 for the i9-9900X, a 5.1% advantage. The single-core R15 test shows a nearly identical gap: 274 versus 261, a 5.0% lead for the i9-11900KB.

Moving to Cinebench R20, the i9-11900KB records 8112 multicore versus 7713 for the i9-9900X, again a 5.2% edge. The single-core R20 result follows the same pattern: 1145 against 1088, a 5.2% difference. In Cinebench R23, the multicore scores are 19316 for the i9-11900KB and 18365 for the i9-9900X, a 5.2% gap. The R23 single-core test closes the set with 2727 versus 2592, also a 5.2% difference.

What stands out is the consistency of the margin. Whether the workload is single-threaded or multi-threaded, the i9-11900KB holds a roughly 5% lead in every recorded benchmark. This is not a case where one chip excels in one area and falls behind in another; the i9-11900KB simply outperforms the i9-9900X across the board. The i9-9900X does have two additional cores (10 versus 8) and four additional threads (20 versus 16), yet it still trails in multicore tests. This indicates that the i9-11900KB's higher boost clock and more efficient architecture more than compensate for the core count deficit.

The average benchmark score in the database reinforces this hierarchy. The i9-11900KB holds an average score of 5587, placing it at the 61st percentile of all CPUs tracked. The i9-9900X averages 5301, sitting at the 60th percentile. The i9-11900KB's nearest rivals are the Intel Atom x7433RE (average 5601, delta -0.2%), the Intel Core i7-12700T (5606, -0.3%), the AMD Ryzen 7 PRO 3700 (5610, -0.4%), and the Intel Celeron G6900 (5561, +0.5%). For the i9-9900X, the closest comparables are the AMD Ryzen Threadripper 1920X (5306, -0.1%), the AMD EPYC 7281 (5315, -0.3%), the Intel Core i9-10900KF (5316, -0.3%), and the Intel Core i9-13900TE (5342, -0.8%). These rival clusters show both processors are surrounded by similar-performing parts, but the i9-11900KB sits slightly higher in the distribution.

The Verdict

The data is unambiguous: the Intel Core i9-11900KB wins all six head-to-head benchmarks against the Intel Core i9-9900X. The margins are small, between 5.0% and 5.2%, but they are consistent across every workload tested. For anyone choosing strictly on recorded Cinebench performance, the i9-11900KB is the better processor. It achieves this with fewer cores (8 versus 10) and fewer threads (16 versus 20), which makes the result even more notable.

The i9-9900X is not without its own strengths, however. The database shows it supports quad-channel memory with a bandwidth of 85.3 GB/s, compared to dual-channel 51.2 GB/s for the i9-11900KB. It also offers 44 PCIe Gen 3 lanes from the CPU, while the i9-11900KB provides 20 PCIe Gen 4 lanes. These are meaningful differences for workloads that rely on memory bandwidth or extensive PCIe expansion, though they do not appear in the Cinebench scores. In the recorded benchmarks, the i9-9900X does not win a single test.

For a buyer focused purely on the measured Cinebench results, the i9-11900KB is the pick. The 5.2% lead in both R20 and R23 multicore tests, alongside similar single-core advantages, makes it the more capable CPU in rendering-style workloads. The i9-9900X remains relevant only if the platform-level features matter more than the benchmark scores, but the data itself favors the i9-11900KB in every recorded test.

FAQ

Q: Which processor has the higher single-core score in Cinebench R23?

A: The Intel Core i9-11900KB scores 2727 in Cinebench R23 single-core, while the Intel Core i9-9900X scores 2592. The i9-11900KB leads by 5.2%.

Q: Does the Intel Core i9-9900X win any head-to-head benchmark?

A: No. Across all six recorded Cinebench tests (R15, R20, and R23, each with multicore and single-core variants), the i9-9900X trails the i9-11900KB in every case. The closest result is the R15 single-core test, where the i9-9900X scores 261 versus 274 for the i9-11900KB, a 5.0% gap.

Q: How do the core and thread counts compare between the two?

A: The i9-9900X has 10 cores and 20 threads, while the i9-11900KB has 8 cores and 16 threads. Despite having fewer cores and threads, the i9-11900KB wins all multicore benchmarks.

Q: What are the average benchmark scores for each processor?

A: The i9-11900KB has an average benchmark score of 5587, and the i9-9900X has an average score of 5301. The i9-11900KB sits at the 61st percentile of all CPUs, while the i9-9900X sits at the 60th percentile.

Q: Which processor has a higher boost clock?

A: The i9-11900KB has a boost clock of 5.30 GHz, compared to 4.50 GHz for the i9-9900X. The base clocks are 3.30 GHz for the i9-11900KB and 3.50 GHz for the i9-9900X.

Q: Do both processors support ECC memory?

A: No. Both the i9-11900KB and the i9-9900X have ECC memory support listed as false in the database.

Specification Differences

The two processors differ in nearly every major specification category. The i9-11900KB uses a BGA 1787 socket, while the i9-9900X uses Socket 2066. The i9-9900X has 10 cores and 20 threads, while the i9-11900KB has 8 cores and 16 threads. Base clock speeds are 3.30 GHz for the i9-11900KB and 3.50 GHz for the i9-9900X, but the boost clocks reverse the order: 5.30 GHz for the i9-11900KB versus 4.50 GHz for the i9-9900X.

Thermal design power differs substantially. The i9-11900KB carries a TDP of 65 watts, while the i9-9900X is rated at 165 watts. The i9-11900KB features integrated graphics (UHD Graphics 750), whereas the i9-9900X has no integrated graphics listed. The i9-11900KB is classified as a mobile processor, while the i9-9900X is a desktop part. Memory channels also separate the two: the i9-11900KB uses dual-channel memory with 51.2 GB/s bandwidth, and the i9-9900X uses quad-channel memory with 85.3 GB/s bandwidth.

PCIe support differs in both generation and lane count. The i9-11900KB offers Gen 4 with 20 CPU lanes, while the i9-9900X offers Gen 3 with 44 CPU lanes. The launch MSRP for the i9-11900KB is $539, while the i9-9900X launched at $989. The release date for the i9-9900X is given as 2018-10-18, while the i9-11900KB has no release date recorded in the database. Both are listed as end-of-life production status, and both have unlocked multipliers.

Architecture Differences

The architectural divide between these two chips is significant. The i9-11900KB is built on Tiger Lake, specifically the Tiger Lake-H generation, using a 10 nm process node from Intel. The i9-9900X is based on Skylake, specifically the Skylake-X generation, on a 14 nm process node. The newer 10 nm process for the i9-11900KB helps explain how it achieves higher boost clocks and better benchmark scores despite a lower TDP.

Cache structures differ as well. The i9-11900KB has 80 KB of L1 cache per core and 1.25 MB of L2 cache per core, with 24 MB of shared L3 cache. The i9-9900X has 64 KB of L1 per core and 1 MB of L2 per core, with 19.25 MB of shared L3 cache. The i9-11900KB therefore has more cache at every level, which contributes to its single-core advantages.

The i9-11900KB uses a die size of 190 mm², while no die size is recorded for the i9-9900X. Both processors use DDR4 memory, and neither supports ECC. The i9-11900KB belongs to the Core 11th Gen series, while the i9-9900X has no series designation listed but is classified under Core i9 X-Series 9th Gen. The integrated graphics on the i9-11900KB are UHD Graphics 750; the i9-9900X has no integrated graphics at all, which is typical for the high-core-count desktop HEDT parts of its era.

The memory controller differences are notable. The i9-11900KB is dual-channel, while the i9-9900X is quad-channel with significantly higher theoretical bandwidth. This does not translate into a benchmark win for the i9-9900X in the recorded Cinebench tests, but it does suggest the i9-9900X may handle memory-intensive workloads differently in untested scenarios. The PCIe layout also tells a story: the i9-9900X has more lanes (44) but older Gen 3 signaling, while the i9-11900KB has fewer lanes (20) but newer Gen 4 signaling.

Where Each One Wins

The Intel Core i9-11900KB wins every recorded benchmark, so the use-case split must be inferred from the specification differences rather than from test results. In Cinebench R15, R20, and R23, both multicore and single-core, the i9-11900KB is ahead by 5.0% to 5.2%. This makes it the clear choice for rendering, video encoding, and other workloads that mirror Cinebench's thread-heavy and single-thread-light patterns. Its higher boost clock of 5.30 GHz and larger L3 cache (24 MB versus 19.25 MB) give it an edge in tasks that respond to per-core performance.

The i9-9900X, despite losing every head-to-head test, has structural advantages that could matter outside the benchmark suite. Its quad-channel memory interface delivers 85.3 GB/s of bandwidth, compared to 51.2 GB/s for the i9-11900KB. Applications that scale with memory bandwidth more than with core clock speed could favor the i9-9900X, though the database does not include such tests. Its 44 PCIe Gen 3 lanes also allow for far more expansion cards, storage devices, or GPUs than the i9-11900KB's 20 Gen 4 lanes. For a workstation with many peripherals, the i9-9900X offers more connectivity.

The i9-9900X also has more cores and threads (10/20 versus 8/16). In workloads that scale perfectly with core count, the i9-9900X should theoretically pull ahead, but the recorded Cinebench multicore results show the opposite: the i9-11900KB wins by 5.1% to 5.2% in all three multicore tests. This suggests the i9-11900KB's architectural efficiency and higher boost clock overcome the core deficit in these specific workloads.

The i9-11900KB, being a mobile-class processor with a 65 watt TDP, is far more power-efficient than the i9-9900X's 165 watt rating. It also includes integrated graphics, which the i9-9900X lacks entirely. For compact systems or builds without a discrete GPU, the i9-11900KB is the only viable option of the two. The i9-9900X requires a discrete graphics card for any display output.

In summary, the i9-11900KB wins on all measured performance, power efficiency, and integrated graphics. The i9-9900X wins on memory bandwidth, PCIe lane count, and raw core count. For users whose primary concern is the recorded Cinebench performance, the i9-11900KB is the definitive choice. For users who need extensive expansion capability or quad-channel memory bandwidth in a desktop workstation, the i9-9900X retains a platform-level appeal that the benchmark scores do not capture.