Intel Xeon 6521P vs Intel Xeon 658X Comparison

FAQ

Q: How do the two processors compare in overall average benchmark score?

A: The Intel Xeon 658X records an average benchmark score of 116060, while the Intel Xeon 6521P sits at 105845. That difference places the 658X roughly 9.7% higher on average, though both sit in the 97th percentile among all CPUs.

Q: Which chip wins the majority of direct benchmark comparisons?

A: The Intel Xeon 658X wins 16 of the 17 head-to-head tests recorded in the database. The Intel Xeon 6521P claims only one win, in PassMark random string sorting, where it leads by 1.4%.

Q: Are the core and thread counts the same?

A: Yes. Both processors feature 24 cores and 48 threads. The performance gap comes from clock speeds and other architectural differences, not from core count.

Q: What are the clock speed differences?

A: The Intel Xeon 658X has a base clock of 3.00 GHz and a boost clock of 4.90 GHz. The Intel Xeon 6521P runs at 2.60 GHz base and 4.10 GHz boost.

Q: Do both processors support the same memory configuration?

A: Both support DDR5 memory with an eight-channel bus and 409.6 GB/s memory bandwidth, and both support ECC memory. PCIe lane counts differ, with the 658X offering Gen 5 with 128 lanes and the 6521P offering Gen 5 with 136 lanes.

Q: Which processor has the higher TDP?

A: The Intel Xeon 658X is rated at 250 W, while the Intel Xeon 6521P is rated at 225 W. The higher power envelope of the 658X aligns with its higher clock speeds.

Architecture Differences

Both processors share the Granite Rapids architecture and are built by Intel on a 5 nm process. The core layout is identical in structure: each core carries 112 KB of L1 cache and 2 MB of L2 cache, and both share a 144 MB L3 cache. The fundamental compute resources are therefore the same on paper, and the measured differences come down to how those resources are clocked and configured.

The Intel Xeon 658X belongs to the Xeon 600 (Granite Rapids-WS) generation, while the Intel Xeon 6521P belongs to the Xeon 6 (Granite Rapids-SP) generation. The die size differs as well: the 658X uses a dual-die arrangement with two 598 mm² dies, while the 6521P uses a single 598 mm² die. That physical difference reflects a different packaging strategy, even though the per-core cache structure is the same.

Clock behavior is the most visible architectural split. The 658X runs a 3.00 GHz base and boosts to 4.90 GHz. The 6521P runs a 2.60 GHz base and boosts to 4.10 GHz. That 0.80 GHz boost advantage for the 658X explains much of its consistent lead in single-threaded and lightly threaded workloads.

The 658X also carries an unlocked multiplier, meaning frequency adjustments are permitted, whereas the 6521P has a locked multiplier. PCIe lane provisioning differs slightly: the 658X exposes Gen 5 with 128 lanes, and the 6521P exposes Gen 5 with 136 lanes. Both use Intel Socket 4710, both lack integrated graphics, and both are aimed at the server and workstation segment. The 658X was released in February 2026, while the 6521P arrived in February 2025.

Head-to-Head Benchmarks

The data shows a consistent pattern: the Intel Xeon 658X leads in nearly every recorded workload, and in most cases by a double-digit margin. Cinebench results are remarkably uniform. In Cinebench R15 multicore, the 658X scores 6296 against 5711 for the 6521P, a 10.2% lead. The single-core R15 result shows the same 10.2% gap, 888 to 806. Cinebench R20 repeats the pattern exactly: 26235 to 23796 in multicore and 3703 to 3359 in single-core, both again 10.2%. Cinebench R23 nudges the margin slightly higher to 10.3% in both multicore and single-core, with scores of 62466 versus 56658 and 8818 versus 7998 respectively.

PassMark results show where the 658X stretches its advantage further. The largest margin comes in floating point math, where the 658X scores 210480 against 178828, a 17.7% lead. Extended instructions follow closely at 16.2%, with scores of 84626 versus 72820. Find prime numbers shows a 15.9% gap, 649 to 560. Single-thread performance in PassMark is 15.1% higher for the 658X, 3728 versus 3238. The multithread test shows a 10.3% lead, 73490 to 66657.

Other workloads show smaller but still meaningful gaps. Data compression favors the 658X by 9.7%, with scores of 1062062 versus 967721. Physics favors it by 8.3%, 6470 to 5972. Integer math is closer at 7.2%, 263995 to 246263. Data encryption is the tightest contest among the 658X wins, just 2.2%, with scores of 52357 and 51221.

The single exception is random string sorting. Here the 6521P takes the win with 104517 against 103028, a 1.4% margin. It is the only recorded test where the 6521P outperforms the 658X, and the margin is small enough to suggest workload-specific behavior rather than a general advantage.

The Verdict

The Intel Xeon 658X is the stronger processor in almost every measurable way. It wins 16 of 17 head-to-head tests, leads in average benchmark score by roughly 9.7%, and posts double-digit margins in Cinebench multicore, Cinebench single-core, PassMark multithread, PassMark single-thread, floating point math, extended instructions, and prime number finding. Its higher base and boost clocks, 3.00 GHz and 4.90 GHz versus 2.60 GHz and 4.10 GHz, translate directly into faster results across rendering, math, encryption, and compression workloads. The 250 W TDP is the price of that performance, and the unlocked multiplier adds flexibility for those who can manage the thermals.

The Intel Xeon 6521P is the more restrained option. It matches the 658X in core count, thread count, L3 cache, memory bandwidth, and ECC support, and it draws 25 W less power. Its 225 W TDP and locked multiplier make it a simpler drop-in part for systems where power and configuration flexibility matter more than peak throughput. Its only benchmark win, random string sorting by 1.4%, is too narrow to change the overall picture.

For workloads that are heavily threaded and latency-sensitive, the 658X is the clear pick. For systems where the 6521P's lower power draw and adequate performance are sufficient, the 6521P remains a viable choice, but the data does not show any area where it meaningfully outperforms the 658X outside that single sorting test.

Specification Differences

The two processors share many specifications, so the differences are concentrated in a few fields. Clock speeds differ significantly: the 658X runs at 3.00 GHz base and 4.90 GHz boost, while the 6521P runs at 2.60 GHz base and 4.10 GHz boost. TDP also differs, with the 658X rated at 250 W and the 6521P at 225 W.

The die configuration is different: the 658X uses two 598 mm² dies, while the 6521P uses a single 598 mm² die. The generation labels differ, with the 658X listed under Xeon 600 (Granite Rapids-WS) and the 6521P under Xeon 6 (Granite Rapids-SP). PCIe lane counts differ slightly: 128 lanes for the 658X versus 136 lanes for the 6521P.

The multiplier is unlocked on the 658X and locked on the 6521P. Release dates differ by roughly a year, with the 658X launching in February 2026 and the 6521P in February 2025. The launch MSRP for the 658X is $1699, and the launch MSRP for the 6521P is $1250. Part numbers also differ: SA2D2 for the 658X and SRVNS for the 6521P.

Identical specifications include 24 cores, 48 threads, 5 nm process from Intel, 112 KB L1 per core, 2 MB L2 per core, 144 MB shared L3, DDR5 memory support, eight-channel memory bus, 409.6 GB/s memory bandwidth, ECC memory support, Intel Socket 4710, no integrated graphics, and the server/workstation market segment.

Where Each One Wins

The Intel Xeon 658X is the choice for compute-heavy workloads that reward clock speed and multithreaded throughput. Cinebench R23 multicore shows a 10.3% lead, and PassMark multithread shows the same 10.3% margin. Floating point math is its strongest area, with a 17.7% advantage, making it well suited for scientific computing, simulation, and rendering tasks. Extended instructions come in 16.2% higher, which points to workloads using SIMD-style operations. Prime number finding is 15.9% faster, and single-thread PassMark is 15.1% higher, so the 658X also handles lightly threaded applications and legacy single-threaded code with more headroom.

Data compression favors the 658X by 9.7%, and integer math by 7.2%. Encryption is closer at 2.2%, but the 658X still leads. Physics workloads show an 8.3% advantage. The unlocked multiplier gives the 658X additional headroom for tuning in systems where cooling and power delivery can support it.

The Intel Xeon 6521P wins only in random string sorting, where it beats the 658X by 1.4%. That is a narrow, workload-specific result. The 6521P is better framed by its lower 225 W TDP and locked multiplier, which make it a more predictable part for power-constrained deployments. It also offers slightly more PCIe lanes at 136 versus 128, which could matter for configurations with many expansion devices. For most measured workloads, though, the 658X is ahead, and the 6521P is best considered when power draw and simplicity take priority over peak benchmark scores.