Intel Core i9-13900KS vs Intel Core Ultra 7 255HX Comparison

The Intel Core i9-13900KS and the Intel Core Ultra 7 255HX represent two very different approaches to high-performance x86 computing: one a desktop flagship from the Raptor Lake generation, the other a mobile part built on Arrow Lake. Benchmark data shows a clear overall winner in raw performance, but the Ultra 7 255HX counters in a few specific workloads. Here is a breakdown of what the numbers actually say.

Head-to-Head Benchmarks

The i9-13900KS dominates the head-to-head comparison, winning 15 of the 17 shared benchmarks. The largest margins appear in single-threaded and heavily multi-threaded workloads. In Cinebench R23 single-core, the i9-13900KS scores 7252 against the Ultra 7 255HX’s 2163, a 235.3% delta. That is not a small edge; it is a generational gap in per-thread performance. The same pattern holds in Cinebench R15 single-core, where the i9 leads by 123.2% (730 vs 327). These results indicate that the 13900KS’s 6.00 GHz boost clock delivers a massive advantage in lightly threaded tasks, despite the newer 3nm process in the Ultra 7.

Multi-core results also favor the desktop chip, though the margins are smaller. In Cinebench R23 multi-core, the i9-13900KS scores 51368 versus 32612 for the Ultra 7, a 57.5% lead. Cinebench R20 multi-core shows a 25.5% advantage (21574 vs 17187). The i9 also wins PassMark integer math by 66% (211027 vs 127126) and data compression by 58.2% (814838 vs 515143). These are substantial wins, reflecting the i9’s 24 cores and 32 threads against the Ultra 7’s 20 cores and 20 threads.

The Ultra 7 255HX does have two wins. The most notable is PassMark find prime numbers, where it scores 400 against the i9’s 257, a -35.7% delta in favor of the mobile chip. This suggests the Arrow Lake architecture has a significant advantage in certain integer-heavy algorithms that do not scale with thread count. The other win is in floating point math, where the Ultra 7 scores 160624 versus 154805, a modest 3.6% lead. These two wins are outliers, but they show that the newer architecture is not without merit in specific compute patterns.

Other benchmarks show closer competition. In PassMark single-thread, the i9 leads by only 3.3% (4712 vs 4562). Cinebench R15 multi-core is also tight, with the i9 ahead by 5.3% (5177 vs 4916). This suggests that in some lightly threaded or short-duration workloads, the Ultra 7 can nearly keep pace, though it falls behind as the workload scales.

Architecture Differences

The two CPUs are built on fundamentally different designs. The i9-13900KS uses Raptor Lake architecture on a 10nm process from Intel, while the Ultra 7 255HX uses Arrow Lake on a 3nm process from TSMC. The die size is close — 257 mm² for the i9 versus 243 mm² for the Ultra 7 — but the transistor count tells a different story. The Ultra 7 packs 17,800 million transistors into that space, whereas the i9’s transistor count is not listed. The smaller node and higher transistor density explain why the Ultra 7 can achieve competitive performance in some tasks despite a much lower power envelope.

Core counts differ significantly. The i9 has 24 cores and 32 threads, while the Ultra 7 has 20 cores and 20 threads. The i9 uses hyper-threading; the Ultra 7 does not. Cache layouts also differ: the i9 has 80 KB of L1 and 2 MB of L2 per core, with 36 MB of shared L3. The Ultra 7 has larger per-core caches — 192 KB L1 and 3 MB L2 — but less shared L3 at 30 MB. This trade-off favors the i9 in cache-heavy multi-threaded workloads, while the larger per-core L2 in the Ultra 7 may help with certain single-threaded patterns.

Memory support is another split. The i9 supports both DDR4 and DDR5, while the Ultra 7 supports DDR5 only. Memory bandwidth is higher on the Ultra 7 at 102.4 GB/s versus 89.6 GB/s for the i9. Both use dual-channel memory buses. ECC memory is supported on the i9 but not on the Ultra 7. PCIe support is identical: Gen 5 with 20 lanes on the CPU. Integrated graphics differ — the i9 has UHD Graphics 770, while the Ultra 7 has Arc Xe-LPG Graphics 64EU.

Where Each One Wins

The i9-13900KS is the clear choice for desktop builds where raw performance is the priority. The data shows it wins in every Cinebench test, both single and multi-core, by margins ranging from 5.3% to 235.3%. It also wins PassMark integer math, data compression, encryption, extended instructions, multithread, physics, random string sorting, and single-thread tests. If you are running video rendering, code compilation, scientific simulations, or any workload that can use 32 threads, the i9’s 57.5% lead in Cinebench R23 multi-core makes it the stronger option. Its 150W TDP and socket LGA 1700 mean it belongs in a desktop with proper cooling.

The Ultra 7 255HX wins only two benchmarks: find prime numbers and floating point math. The prime number win is notable — a 35.7% lead over the i9 — which suggests that certain mathematical algorithms, possibly those involving modular arithmetic, run significantly better on the Arrow Lake design. The floating point win is smaller at 3.6%, but it indicates that the Ultra 7 is not entirely outclassed in compute-heavy tasks. This makes the Ultra 7 a viable option for laptop users who need strong floating-point performance in a mobile form factor, particularly if the workload is not heavily threaded. Its 55W TDP and BGA 2114 socket also point to a power-efficient design.

Specification Differences

The two CPUs differ in nearly every major specification. The i9-13900KS has 24 cores and 32 threads; the Ultra 7 255HX has 20 cores and 20 threads. Base clocks are 3.20 GHz for the i9 and 2.40 GHz for the Ultra 7. Boost clocks are 6.00 GHz and 5.20 GHz, respectively. TDP is 150W for the i9 and 55W for the Ultra 7. Sockets are Intel Socket 1700 for the i9 and Intel BGA 2114 for the Ultra 7. The i9 is a desktop part; the Ultra 7 is mobile. Release dates are January 2023 for the i9 and January 2025 for the Ultra 7. The i9 has a launch MSRP of $699; the Ultra 7 has no listed MSRP. Both have unlocked multipliers. The i9 supports ECC memory; the Ultra 7 does not. Memory support is DDR4/DDR5 on the i9 and DDR5-only on the Ultra 7. L3 cache is 36 MB on the i9 and 30 MB on the Ultra 7.

FAQ

Q: Which CPU is faster in single-threaded performance?

A: The i9-13900KS. In Cinebench R23 single-core, it scores 7252 against the Ultra 7 255HX’s 2163, a 235.3% advantage. It also leads by 123.2% in Cinebench R15 single-core.

Q: Does the Ultra 7 255HX win any benchmarks?

A: Yes, two. It wins PassMark find prime numbers (400 vs 257) and PassMark floating point math (160624 vs 154805). These are the only wins in the shared test suite.

Q: How do the core counts compare?

A: The i9-13900KS has 24 cores and 32 threads, while the Ultra 7 255HX has 20 cores and 20 threads. The i9 supports hyper-threading; the Ultra 7 does not.

Q: What is the memory bandwidth difference?

A: The Ultra 7 255HX has higher memory bandwidth at 102.4 GB/s, while the i9-13900KS has 89.6 GB/s. Both use dual-channel memory, but the i9 supports DDR4 and DDR5, while the Ultra 7 is DDR5-only.

Q: Which CPU has a larger L3 cache?

A: The i9-13900KS has 36 MB of shared L3 cache, compared to 30 MB on the Ultra 7 255HX. However, the Ultra 7 has larger per-core L1 (192 KB vs 80 KB) and L2 (3 MB vs 2 MB) caches.

Q: Are both CPUs unlocked for overclocking?

A: Yes, both have unlocked multipliers. The i9-13900KS is a desktop part with a 150W TDP, while the Ultra 7 255HX is mobile with a 55W TDP.

The Verdict

The Intel Core i9-13900KS is the superior processor for raw performance. It wins 15 of 17 benchmark comparisons, with decisive leads in both single-threaded and multi-threaded workloads. The data shows it is 57.5% ahead in Cinebench R23 multi-core and 235.3% ahead in Cinebench R23 single-core. If you are building a desktop workstation or gaming rig and need maximum compute throughput, the i9-13900KS is the pick. Its 36 MB L3 cache, 24 cores, and 32 threads give it a clear edge in heavily parallel tasks. The launch MSRP of $699 reflects its flagship status.

The Intel Core Ultra 7 255HX is the choice for mobile users who need a balance of performance and efficiency. Its 55W TDP and 3nm process make it suitable for laptops. The two benchmark wins — prime number finding and floating point math — indicate that Arrow Lake has strengths in specific computational patterns. However, the data shows it is not competitive with the i9 in most workloads. For a laptop CPU, it is a capable part, but it cannot match the desktop i9 in sustained multi-threaded performance. Choose the Ultra 7 only if you require a mobile form factor and those two specific workload types are your priority. For everything else, the i9-13900KS is the data-backed winner.