CPU Comparison

The Intel Core i5-2550K and the Intel Xeon E5640 land in the same performance tier, with near-identical average benchmark scores (1136 vs 1137) and matching 32nd-percentile rankings. However, the data reveals a clear split: the i5-2550K wins every head-to-head benchmark, while the Xeon E5640 counters with platform-level advantages in memory bandwidth, ECC support, and thread count. This comparison is not about a knockout but about which trade-offs matter more for a specific workload.

Head-to-Head Benchmarks

The benchmark results are unambiguous in favor of the Intel Core i5-2550K, which claims victories in all five head-to-head tests. In Cinebench R15 multicore, the i5-2550K scores 365 against the Xeon E5640's 332, a 9% advantage. The pattern repeats in Cinebench R20 multicore, where the i5-2550K posts 1523 versus 1387, an 8.9% lead. The gap narrows slightly in Cinebench R23 multicore, with the i5-2550K at 3628 and the Xeon E5640 at 3303, still a 9% margin.

Single-core performance tells the same story. In Cinebench R20 single-core, the i5-2550K scores 215 compared to the Xeon E5640's 195, a 9.3% difference. Cinebench R23 single-core shows the i5-2550K at 512 against the Xeon E5640's 466, again a 9% lead. The i5-2550K also has additional benchmark data points not available for the Xeon E5640, including Geekbench multicore (2096) and single-core (697) scores, which further reinforce its performance edge.

The consistency of these results is notable. Every Cinebench iteration, from R15 through R23, shows the same approximate 9% delta favoring the i5-2550K. This suggests the performance gap is structural rather than workload-specific. The Xeon E5640's higher thread count (8 threads versus 4) does not compensate for the i5-2550K's higher clock speeds in these tests. The i5-2550K's base clock of 3.40 GHz and boost clock of 3.80 GHz substantially exceed the Xeon E5640's 2.67 GHz base and 2.93 GHz boost, and the benchmark data confirms that raw clock speed wins out over additional threads in this comparison.

Architecture Differences

The two processors come from different Intel generations and target different market segments. The Xeon E5640 is a Westmere-EP server/workstation chip launched in 2010, built on the 32 nm process with 1,170 million transistors on a 239 mm² die. The Core i5-2550K is a Sandy Bridge desktop processor launched in 2012, also on 32 nm but with 1,160 million transistors on a smaller 216 mm² die. The transistor counts are nearly identical, differing by only 10 million, but the die size difference indicates architectural changes.

Cache configurations differ significantly. Both have 64 KB L1 cache per core and 256 KB L2 cache per core, but the shared L3 cache tells a different story: the Xeon E5640 has 12 MB shared L3, while the i5-2550K has 6 MB. The Xeon E5640's larger cache is a direct consequence of its server-oriented design, where larger working sets are common. However, the benchmark results show that this cache advantage does not translate into performance wins in the tested Cinebench workloads.

Memory support provides the most substantial architectural divergence. The Xeon E5640 supports triple-channel DDR3 with ECC memory, while the i5-2550K uses dual-channel DDR3 without ECC. The i5-2550K has a listed memory bandwidth of 25.6 GB/s, while the Xeon E5640's bandwidth is not specified in the data. The Xeon E5640's ECC support and triple-channel configuration make it suitable for error-sensitive server environments, whereas the i5-2550K's dual-channel setup is typical of consumer desktops. Both use PCIe Gen 2, but the i5-2550K offers 16 lanes from the CPU, while the Xeon E5640's lane configuration is not specified.

The socket and platform requirements reinforce this split. The Xeon E5640 uses Intel Socket 1366, while the i5-2550K uses Intel Socket 1155. These are incompatible platforms with different chipsets and feature sets. The i5-2550K has an unlocked multiplier, enabling overclocking, while the Xeon E5640's multiplier is locked. Neither processor includes integrated graphics, and both are end-of-life products.

Where Each One Wins

The Intel Core i5-2550K wins decisively in raw computational performance across all tested benchmarks. Its higher clock speeds deliver a consistent 9% advantage in both single-core and multicore Cinebench tests. This makes it the stronger choice for applications that prioritize per-thread performance, such as legacy single-threaded software, lightly threaded productivity apps, and games from its era. The unlocked multiplier adds flexibility for enthusiasts willing to push clock speeds further, though the data does not quantify overclocking results.

The Intel Xeon E5640 wins in platform-level features rather than benchmark scores. Its 8 threads (versus 4) provide better handling of heavily threaded workloads, even if the Cinebench multicore results do not reflect this advantage. The triple-channel memory bus offers higher theoretical memory bandwidth than the i5-2550K's dual-channel setup, which could benefit memory-intensive server applications. ECC memory support is the Xeon's most distinctive feature, providing error correction that is essential for data integrity in servers and workstations. The larger 12 MB L3 cache (versus 6 MB) may also help with workloads that exhibit high cache locality.

The market segments tell the story. The Xeon E5640 targets server and workstation environments where ECC, memory bandwidth, and thread count matter more than raw clock speed. The i5-2550K targets desktop users who value single-thread performance and overclocking headroom. Neither processor is a clear winner for all use cases; the choice depends on whether the workload is latency-sensitive (favoring the i5-2550K) or throughput-oriented with error-correction requirements (favoring the Xeon E5640).

FAQ

Q: Which processor is faster in Cinebench R23 multicore?

A: The Intel Core i5-2550K scores 3628 versus the Intel Xeon E5640's 3303, a 9% advantage.

Q: Does the Xeon E5640's 8 threads help in benchmarks?

A: No. Despite having 8 threads versus 4, the Xeon E5640 loses every head-to-head Cinebench test to the i5-2550K by approximately 9%.

Q: Which processor supports ECC memory?

A: Only the Intel Xeon E5640 supports ECC memory. The Intel Core i5-2550K does not.

Q: Are these processors overclockable?

A: The Intel Core i5-2550K has an unlocked multiplier, while the Intel Xeon E5640's multiplier is locked.

Q: What are the memory channel configurations?

A: The Xeon E5640 supports triple-channel DDR3, while the i5-2550K uses dual-channel DDR3. The i5-2550K has a specified bandwidth of 25.6 GB/s.

Q: How do their average benchmark scores compare?

A: They are effectively tied. The Xeon E5640 has an average benchmark score of 1137, and the i5-2550K has 1136, a 0.1% difference.

The Verdict

The data supports the Intel Core i5-2550K for any application that depends on single-thread performance or raw clock speed. It wins all five head-to-head Cinebench tests with a consistent 9% margin, and its unlocked multiplier offers overclocking potential that the Xeon E5640 cannot match. For gaming, desktop productivity, and legacy software that favors high clock speeds, the i5-2550K is the clear choice.

The Intel Xeon E5640 is the better pick for server and workstation environments where ECC memory support and triple-channel memory bandwidth are non-negotiable requirements. Its 8 threads provide headroom for multi-threaded server workloads, and its larger 12 MB L3 cache may benefit specific data-intensive tasks. The fact that it loses all benchmarks does not disqualify it; rather, it signals that the Xeon E5640's value lies outside the tested metrics. Users who need error-correcting memory or a platform designed for 24/7 reliability should choose the Xeon E5640. Users who prioritize speed in consumer applications should choose the i5-2550K.

Specification Differences

| Specification | Intel Xeon E5640 | Intel Core i5-2550K |

|---|---|---|

| Cores | 4 | 4 |

| Threads | 8 | 4 |

| Base Clock | 2.67 GHz | 3.40 GHz |

| Boost Clock | 2.93 GHz | 3.80 GHz |

| TDP | 80 W | 95 W |

| Socket | Intel Socket 1366 | Intel Socket 1155 |

| Architecture | Westmere | Sandy Bridge |

| Transistors | 1,170 million | 1,160 million |

| Die Size | 239 mm² | 216 mm² |

| L3 Cache | 12 MB (shared) | 6 MB (shared) |

| Memory Bus | Triple-channel | Dual-channel |

| Memory Bandwidth | Not specified | 25.6 GB/s |

| ECC Memory | Yes | No |

| PCIe | Gen 2 | Gen 2, 16 Lanes (CPU only) |

| Market Segment | Server/Workstation | Desktop |

| Release Date | 2010-03-15 | 2012-01-29 |

| Launch MSRP | Not specified | $235 |

| Multiplier Unlocked | No | Yes |

| Part Number | SLBVC | SR0QH |