AMD EPYC 9255 vs Intel Xeon 6521P Comparison

Head-to-Head Benchmarks

The benchmark data presents a remarkably consistent picture: the AMD EPYC 9255 wins all 17 recorded comparisons against the Intel Xeon 6521P. No benchmark in the database favors the Intel part. The margins, however, vary significantly across workload types, and those variations reveal where each architecture's strengths and weaknesses lie.

The most decisive victory comes in the PassMark physics test, where the AMD EPYC 9255 scores 9,740 against Intel's 5,972, a staggering 63.1% advantage. This is not a marginal difference; it suggests a fundamental gap in how the two processors handle physics simulation workloads. Integer math also shows a wide gulf, with AMD scoring 306,442 versus Intel's 246,263, a 24.4% lead. Random string sorting follows at 23.6% ahead, with AMD scoring 129,202 against 104,517.

The Cinebench suite tells a story of consistent, uniform superiority. Across R15, R20, and R23, in both single-core and multi-core tests, the AMD EPYC 9255 leads by exactly 13.5% in every instance. The multi-core scores are 6,483 vs 5,711 (R15), 27,013 vs 23,796 (R20), and 64,318 vs 56,658 (R23). Single-core results show the same 13.5% gap: 915 vs 806 (R15), 3,813 vs 3,359 (R20), and 9,080 vs 7,998 (R23). This uniformity across different Cinebench versions suggests a consistent architectural advantage rather than workload-specific optimization.

The data encryption test shows a 16.5% gap (59,668 vs 51,221), while PassMark multithread performance lands at 14.9% (76,580 vs 66,657). Single-thread performance in PassMark shows a 12.9% delta (3,655 vs 3,238). The narrower margins appear in data compression at 5.3% (1,018,904 vs 967,721), extended instructions at 3.2% (75,185 vs 72,820), prime number finding at 3.6% (580 vs 560), and floating-point math at 2.5% (183,367 vs 178,828).

The average benchmark score calculation places the AMD EPYC 9255 at 116,388 with a 97th percentile ranking among all CPUs. The Intel Xeon 6521P averages 105,845, also in the 97th percentile. When placed against their nearest rivals, the AMD part sits 0.3% above the Intel Xeon 658X and 1% above the Intel Xeon 6527P, while trailing the Intel Xeon w7-3565X by 1.6% and the AMD EPYC 9384X by 3.4%. The Intel Xeon 6521P, by contrast, sits 0.3% below the Intel Xeon w7-3555 and 0.5% below the AMD Ryzen 9 9850HX, while leading the AMD EPYC 8324P by 2.4% and trailing the Intel Xeon w7-2595X by 2.6%.

Architecture Differences

The two processors take fundamentally different approaches to achieving their core counts. Both offer 24 cores and 48 threads, but the underlying designs diverge sharply.

The AMD EPYC 9255 uses the Zen 5 architecture under the Turin codename, built on TSMC's 4 nm process. It integrates 33,260 million transistors across a multi-chiplet design with four dies, each measuring 70.6 mm². The cache hierarchy allocates 80 KB of L1 and 1 MB of L2 per core, with a shared 128 MB L3 cache. Memory support runs through a twelve-channel DDR5 bus delivering 576.0 GB/s of bandwidth. PCIe connectivity provides Gen 5 with 128 lanes from the CPU.

The Intel Xeon 6521P employs the Granite Rapids architecture, built on Intel's 5 nm process with a monolithic die measuring 598 mm². The cache layout differs notably: 112 KB of L1 and 2 MB of L2 per core, with a larger shared 144 MB L3 cache. Memory runs on an eight-channel DDR5 bus with 409.6 GB/s bandwidth. PCIe capabilities extend to Gen 5 with 136 lanes from the CPU.

These architectural choices explain several benchmark patterns. The AMD part's significantly higher memory bandwidth (576.0 vs 409.6 GB/s) likely contributes to its large leads in data encryption and random string sorting, both memory-sensitive workloads. The Intel part's larger per-core L2 cache (2 MB vs 1 MB) and bigger L3 (144 MB vs 128 MB) did not translate into benchmark wins, suggesting the AMD memory subsystem and core design compensate effectively.

Clock speeds also differ substantially. The AMD EPYC 9255 runs at a 3.25 GHz base clock and boosts to 4.80 GHz. The Intel Xeon 6521P operates at 2.60 GHz base and 4.10 GHz boost. The thermal design power favors AMD at 200W versus Intel's 225W. The AMD part achieves its higher performance at a lower power envelope, a meaningful efficiency indicator.

FAQ

Q: Which processor has the higher boost clock speed?

A: The AMD EPYC 9255 boosts to 4.80 GHz, while the Intel Xeon 6521P reaches 4.10 GHz. The AMD part also has a higher base clock at 3.25 GHz versus 2.60 GHz.

Q: How much faster is the AMD EPYC 9255 in Cinebench multi-core tests?

A: The AMD EPYC 9255 leads by exactly 13.5% across all three Cinebench versions tested. The R23 multi-core scores show 64,318 for AMD versus 56,658 for Intel.

Q: What is the single most lopsided benchmark result between these two CPUs?

A: The PassMark physics test shows the largest gap, with the AMD EPYC 9255 scoring 9,740 against Intel's 5,972, a 63.1% advantage.

Q: Do both processors support ECC memory?

A: Yes, both the AMD EPYC 9255 and the Intel Xeon 6521P support ECC memory. Both also use DDR5 memory, though AMD has a twelve-channel interface while Intel uses eight channels.

Q: How do these processors compare in data compression workloads?

A: The AMD EPYC 9255 scores 1,018,904 in PassMark data compression versus 967,721 for Intel, a 5.3% lead. This is one of the narrower margins between the two parts.

Q: Which CPU has more PCIe lanes?

A: The Intel Xeon 6521P provides 136 PCIe Gen 5 lanes from the CPU, while the AMD EPYC 9255 offers 128 lanes. Both support PCIe Gen 5.

Specification Differences

The recorded specifications differ across nearly every major category. The AMD EPYC 9255 uses the Zen 5 architecture on TSMC's 4 nm process, while Intel employs Granite Rapids on its 5 nm process. AMD's design uses four 70.6 mm² dies with 33,260 million transistors; Intel uses a single 598 mm² die with no transistor count recorded.

Cache allocations diverge: AMD provides 80 KB L1 and 1 MB L2 per core with 128 MB shared L3. Intel provides 112 KB L1 and 2 MB L2 per core with 144 MB shared L3. Memory channels favor AMD at twelve versus Intel's eight, yielding 576.0 GB/s versus 409.6 GB/s bandwidth. PCIe lanes favor Intel at 136 versus 128. Base clocks favor AMD at 3.25 GHz versus 2.60 GHz, as do boost clocks at 4.80 GHz versus 4.10 GHz. TDP favors AMD at 200W versus 225W. Sockets differ: AMD Socket SP5 versus Intel Socket 4710.

The release dates also differ, with AMD launching on October 9, 2024, and Intel on February 23, 2025. The launch MSRP for the AMD EPYC 9255 is $2495, while the Intel Xeon 6521P lists at $1250.

Where Each One Wins

Based on the recorded data, the AMD EPYC 9255 wins every benchmark category, but the magnitude of those wins varies enough to suggest distinct workload suitability.

For physics simulation and integer-heavy workloads, the AMD part is transformative. The 63.1% physics lead and 24.4% integer math advantage indicate workloads in scientific computing, engineering simulation, and data processing would see substantial gains. The 23.6% edge in random string sorting also points to strong performance in data manipulation and text processing tasks.

The Cinebench results, consistent at 13.5% across all versions, show the AMD part delivers broadly superior rendering and content creation performance. The 14.9% multithread advantage and 12.9% single-thread advantage reinforce this pattern for both fully threaded and lightly threaded workloads.

The Intel Xeon 6521P, despite losing all 17 benchmarks, comes closest in floating-point math (2.5% gap), extended instructions (3.2%), and prime number finding (3.6%). These relatively narrow margins suggest that for pure floating-point computation and certain instruction-heavy workloads, the Intel part is competitive. The 5.3% data compression gap also falls on the narrower end. For workloads dominated by these specific operations, the Intel processor would not present a significant disadvantage.

The Intel part's larger L3 cache and higher PCIe lane count may benefit specific deployment scenarios, though no benchmark in the database directly measures those advantages.

The Verdict

The benchmark data is unambiguous: the AMD EPYC 9255 outperforms the Intel Xeon 6521P in every recorded test, with margins ranging from 2.5% to 63.1%. The AMD part achieves this while running at a lower TDP (200W versus 225W) and offering higher memory bandwidth (576.0 GB/s versus 409.6 GB/s).

Organizations deploying for physics simulation, integer processing, or data sorting workloads should strongly favor the AMD EPYC 9255, given the substantial margins in those specific tests. The consistent 13.5% Cinebench advantage also makes the AMD part the clear choice for rendering and content creation workloads.

The Intel Xeon 6521P remains competitive in floating-point math and extended instruction workloads, where the gap narrows to single digits. Its lower launch MSRP of $1250 versus $2495 for the AMD part may factor into procurement decisions, though the database records no price-performance metrics.

For workloads concentrated in floating-point operations, the Intel part could serve adequately. For essentially every other measured workload, the data indicates the AMD EPYC 9255 delivers superior performance, often by substantial margins. The 97th percentile ranking for both parts shows they sit among the top processors in the database, but the AMD EPYC 9255's average benchmark score of 116,388 versus 105,845 for the Intel Xeon 6521P reflects its broader and deeper performance advantage.