Intel Core i7-3960X vs Intel Xeon E3-1275 v5 Comparison

The Intel Xeon E3-1275 v5 and Intel Core i7-3960X occupy similar overall performance tiers despite being separated by four years of architecture evolution. The data shows a remarkably consistent pattern: the Core i7-3960X, a six-core Sandy Bridge-E part, edges out the four-core Skylake Xeon in every single benchmark recorded, though by margins that rarely exceed 2%. This head-to-head comparison is defined not by a decisive victory, but by the narrowness of the older chip's lead.

Head-to-Head Benchmarks

The Core i7-3960X wins all six recorded head-to-head comparisons, but the deltas are small. In Cinebench R15 multi-core, the i7-3960X scores 722 against the Xeon's 712, a 1.4% advantage. The single-core R15 test shows a similar gap: 102 versus 100, a 2% lead for the i7. Moving to Cinebench R20, the i7-3960X posts 3011 multi-core and 425 single-core, while the Xeon E3-1275 v5 manages 2967 and 418 respectively. The deltaPct here is -1.5% for multi-core and -1.6% for single-core, both favoring the i7.

The pattern holds in Cinebench R23. The i7-3960X scores 7170 multi-core and 1012 single-core; the Xeon scores 7065 and 997. The deltas are -1.5% in both cases. Across all six tests, the i7-3960X wins by margins ranging from 1.4% to 2.0%. No test produces a delta larger than 2%, and none favors the Xeon. The average benchmark scores confirm the near-parity: the Xeon E3-1275 v5 averages 2043, while the i7-3960X averages 2037. Both sit at the 45th percentile of all CPUs, and their nearest rivals are nearly identical — the Xeon's closest competitor is the AMD Ryzen 5 7520U at 2046 (-0.1%), while the i7's closest is the AMD Opteron 6386 SE at 2038 (0%).

The interpretation here is straightforward. The i7-3960X's two additional physical cores and four additional threads provide a small but consistent advantage in multi-threaded workloads. Its single-core wins, though narrower, suggest that the older Sandy Bridge architecture's higher per-core performance in these specific Cinebench tests is sufficient to overcome the Xeon's newer Skylake design. The data does not support a narrative of the newer chip leapfrogging the older one; rather, it shows two processors locked in a statistical tie, with the i7 holding a slight edge across every workload measured.

Architecture Differences

The two processors represent different Intel design eras. The Xeon E3-1275 v5 is built on the Skylake architecture, specifically Skylake-DT, using a 14 nm process node. It contains 1,750 million transistors on a 122 mm² die. The Core i7-3960X uses the Sandy Bridge architecture, specifically Sandy Bridge-E, on a 32 nm process. It packs 2,270 million transistors onto a much larger 435 mm² die. The transistor count is higher on the older chip, but the newer 14 nm node allows the Xeon to fit far more density per square millimeter.

Core and cache configurations differ significantly. The Xeon has 4 cores and 8 threads, while the i7-3960X has 6 cores and 12 threads. Both share the same L1 cache structure at 64 KB per core and the same L2 cache at 256 KB per core. The L3 cache is where the gap widens: the Xeon has 8 MB shared, while the i7-3960X has 15 MB shared — nearly double. This larger cache likely contributes to the i7's slight single-core wins, as more data can be held closer to the execution units.

Memory support diverges substantially. The Xeon supports both DDR3 and DDR4 memory in a dual-channel configuration, providing 34.1 GB/s of memory bandwidth. The i7-3960X supports only DDR3, but in a quad-channel configuration, yielding 51.2 GB/s — 50% more bandwidth. The i7 also offers 40 PCIe Gen 3 lanes from the CPU, versus the Xeon's 16 lanes. The Xeon does include integrated graphics (HD Graphics P530), while the i7 has none. The Xeon supports ECC memory; the i7 does not.

Socket and platform targets differ as well. The Xeon uses Intel Socket 1151 and is classified as a Server/Workstation part. The i7-3960X uses Intel Socket 2011 and is classified as Desktop. The Xeon's multiplier is locked, while the i7-3960X's multiplier is unlocked, allowing overclocking. The i7 was released on 2011-11-13 with a launch MSRP of $990; the Xeon was released on 2015-10-18 with a launch MSRP of $350. Both are end-of-life products.

FAQ

Q: Which processor has the higher average benchmark score?

A: The Intel Xeon E3-1275 v5 has an average benchmark score of 2043, while the Intel Core i7-3960X has an average of 2037. The Xeon is 6 points higher, but both sit at the 45th percentile of all CPUs.

Q: Does the Core i7-3960X win in every head-to-head benchmark?

A: Yes. The i7-3960X wins all six recorded head-to-head tests, with deltaPct values ranging from -1.4% to -2.0% in its favor. The largest win is in Cinebench R15 single-core, where it leads by 2 points (102 vs 100).

Q: How do the core counts and memory bandwidth compare?

A: The i7-3960X has 6 cores and 12 threads, while the Xeon E3-1275 v5 has 4 cores and 8 threads. The i7 also has higher memory bandwidth at 51.2 GB/s (quad-channel DDR3) versus the Xeon's 34.1 GB/s (dual-channel DDR3/DDR4).

Q: Does the Xeon support ECC memory?

A: Yes, the Xeon E3-1275 v5 supports ECC memory. The Core i7-3960X does not support ECC memory.

Q: What is the difference in process node and die size?

A: The Xeon is built on a 14 nm process with a 122 mm² die containing 1,750 million transistors. The i7-3960X uses a 32 nm process with a 435 mm² die containing 2,270 million transistors.

Q: Which processor has a larger L3 cache?

A: The Core i7-3960X has a 15 MB shared L3 cache, compared to the Xeon E3-1275 v5's 8 MB shared L3 cache. Both have identical L1 and L2 cache sizes per core.

Specification Differences

• Cores: Xeon E3-1275 v5 has 4; Core i7-3960X has 6.
• Threads: Xeon has 8; i7-3960X has 12.
• Base Clock: Xeon is 3.60 GHz; i7-3960X is 3.30 GHz.
• Boost Clock: Xeon is 4.00 GHz; i7-3960X is 3.90 GHz.
• TDP: Xeon is 80W; i7-3960X is 130W.
• Socket: Xeon uses Intel Socket 1151; i7-3960X uses Intel Socket 2011.
• Architecture: Xeon is Skylake; i7-3960X is Sandy Bridge.
• Process Node: Xeon is 14 nm; i7-3960X is 32 nm.
• Transistors: Xeon has 1,750 million; i7-3960X has 2,270 million.
• Die Size: Xeon is 122 mm²; i7-3960X is 435 mm².
• L3 Cache: Xeon has 8 MB shared; i7-3960X has 15 MB shared.
• Memory Support: Xeon supports DDR3 and DDR4; i7-3960X supports only DDR3.
• Memory Bus: Xeon is dual-channel; i7-3960X is quad-channel.
• Memory Bandwidth: Xeon is 34.1 GB/s; i7-3960X is 51.2 GB/s.
• ECC Memory: Xeon supports it; i7-3960X does not.
• PCIe Lanes: Xeon has 16 lanes (Gen 3); i7-3960X has 40 lanes (Gen 3).
• Integrated Graphics: Xeon has HD Graphics P530; i7-3960X has none.
• Market Segment: Xeon is Server/Workstation; i7-3960X is Desktop.
• Multiplier Unlocked: Xeon is locked; i7-3960X is unlocked.
• Launch MSRP: Xeon is $350; i7-3960X is $990.

The Verdict

The benchmark data shows a clear, if narrow, winner: the Intel Core i7-3960X. It wins every head-to-head test, with the largest margin being 2% in Cinebench R15 single-core and the smallest being 1.4% in Cinebench R15 multi-core. The i7's advantage stems from its two additional cores and four additional threads, which provide a structural edge in multi-threaded workloads, and its larger 15 MB L3 cache, which likely aids single-threaded performance. The Xeon's newer 14 nm process and lower 80W TDP do not translate into benchmark wins in this comparison.

However, the i7-3960X's victory is not a rout. The Xeon E3-1275 v5 matches it within 2% on every test, and both processors land at the same 45th percentile of all CPUs. The Xeon's average benchmark score is actually 6 points higher than the i7's, though this is within the noise of the nearest rivals. The Xeon also brings features the i7 lacks: ECC memory support, integrated graphics, and compatibility with DDR4 memory. For a buyer prioritizing benchmark performance in Cinebench workloads, the i7-3960X is the pick. For a buyer prioritizing platform features like ECC or onboard graphics, the Xeon is the only option that provides them.

Where Each One Wins

Intel Core i7-3960X: Wins all six recorded Cinebench benchmarks, including both multi-core and single-core tests in R15, R20, and R23. Its largest advantage is 2% in Cinebench R15 single-core (102 vs 100). It also offers quad-channel memory bandwidth at 51.2 GB/s, 40 PCIe Gen 3 lanes, an unlocked multiplier, and a 15 MB shared L3 cache. It is the better choice for raw rendering performance in Cinebench workloads and for users who want the flexibility of overclocking.

Intel Xeon E3-1275 v5: Wins no head-to-head benchmarks, but its average benchmark score is 2043 versus the i7's 2037, a 6-point lead. It provides ECC memory support, integrated HD Graphics P530, DDR4 memory compatibility, a lower 80W TDP, and a smaller 122 mm² die on a more efficient 14 nm process. It is the better choice for server or workstation environments requiring ECC memory, for systems needing integrated graphics, or for builds where lower power consumption and a smaller physical footprint matter more than a 1.4-2.0% benchmark delta.