Intel Core i5-5257U vs Intel Core i7-875K Comparison

The Intel Core i7-875K and Intel Core i5-5257U are two fundamentally different processors that happen to land near each other in aggregate benchmark scores. The data shows a clear split: the i7-875K wins 5 of 7 head-to-head tests, while the i5-5257U takes the remaining 2, but the margins and the nature of those wins tell the real story. The i7-875K is the multi-threaded rendering champion, while the i5-5257U delivers a crushing single-core advantage in Geekbench, making it the better choice for lightly-threaded, latency-sensitive workloads.

Where Each One Wins

The i7-875K dominates the Cinebench suite across the board. In cinebench_r15_multicore, it scores 275 versus 242 for the i5-5257U, a 13.6% advantage. The pattern repeats in cinebench_r20_multicore (1146 vs 1010, +13.5%), cinebench_r23_multicore (2729 vs 2406, +13.4%), and even in single-core Cinebench tests, where the i7-875K leads by 13.4% in r20_singlecore (161 vs 142) and 13.6% in r23_singlecore (385 vs 339). This is a complete sweep of the Cinebench tests, indicating that the older Nehalem architecture’s 4 cores and 8 threads provide a decisive edge in rendering workloads that scale with thread count and sustained throughput.

The i5-5257U’s wins are concentrated in Geekbench, and they are dramatic. In geekbench_multicore, it scores 1773 against the i7-875K’s 1696, a 4.3% margin. But the headline result is geekbench_singlecore: 922 versus 499, a staggering 45.9% advantage for the i5-5257U. This is not a marginal win; it is a generational leap in per-core efficiency. The Broadwell architecture’s 14 nm process and modern design deliver nearly double the single-thread performance in this specific workload, which reflects real-world responsiveness in applications that rely on one or two heavily-utilized cores.

Architecture Differences

The two CPUs come from opposite ends of Intel’s design philosophy. The i7-875K is a Lynnfield desktop part built on the Nehalem architecture, fabricated on a 45 nm process with 774 million transistors on a 296 mm² die. It features 4 cores and 8 threads, with a base clock of 2.93 GHz and a boost clock of 3.60 GHz. Its cache layout includes 64 KB L1 per core, 256 KB L2 per core, and 8 MB of shared L3. It supports DDR3 memory over a dual-channel bus with 21.3 GB/s of bandwidth, and it has an unlocked multiplier, making it a desktop enthusiast part.

The i5-5257U is a Broadwell-U mobile chip, built on a 14 nm process with 1,900 million transistors packed into a 133 mm² die. It has only 2 cores and 4 threads, running at a base clock of 2.70 GHz and a boost clock of 3.10 GHz. Its cache is much smaller: 64 KB L1 per core, 256 KB L2 per core, and just 3 MB of shared L3. It supports DDR3 over dual-channel with higher bandwidth at 29.9 GB/s. It also integrates Intel Iris 6100 graphics, which the i7-875K lacks entirely. The i5-5257U’s multiplier is locked, and its socket is BGA 1168, meaning it is soldered to the motherboard.

The architectural gap is vast. The i7-875K relies on raw core count and high clock speeds from 2010, while the i5-5257U leverages a 14 nm process from 2015 to achieve higher efficiency per clock. The transistor count difference—1,900 million versus 774 million—reflects the integration of newer features and the Iris 6100 GPU. The die size difference (133 mm² vs 296 mm²) shows how process shrinkage enables far more transistors in less space.

Head-to-Head Benchmarks

The Cinebench results are the i7-875K’s strongest statement. In cinebench_r15_multicore, the 275 vs 242 score gives it a 13.6% lead. The same margin appears in cinebench_r23_singlecore (385 vs 339, +13.6%), which is notable because single-core tests typically favor newer architectures. The i7-875K’s higher boost clock of 3.60 GHz versus 3.10 GHz likely explains this, as does the fact that the i5-5257U’s lower TDP of 28 W forces more aggressive power management.

The Geekbench results flip the script entirely. In geekbench_singlecore, the i5-5257U scores 922 versus 499, a 45.9% advantage that is the largest margin in any test. This is a massive gap that cannot be explained by clock speed alone; it points to a fundamental improvement in instruction-level efficiency and memory latency in the Broadwell core. In geekbench_multicore, the i5-5257U still wins, 1773 vs 1696, but by a much smaller 4.3% margin, since the i7-875K’s extra cores help close the gap.

The overall win count is 5-2 in favor of the i7-875K, but that statistic is misleading. The i5-5257U’s single-core Geekbench win is so large that it dominates real-world desktop responsiveness, while the i7-875K’s Cinebench wins are consistent but narrower. The average benchmark scores are nearly identical—984 for the i7-875K and 976 for the i5-5257U—placing both CPUs at the 27th and 26th percentiles of all CPUs respectively.

Specification Differences

The two processors differ in nearly every key specification. The i7-875K has twice the cores (4 vs 2) and twice the threads (8 vs 4). Its base clock is higher at 2.93 GHz versus 2.70 GHz, and its boost clock is 3.60 GHz versus 3.10 GHz. The TDP is 95 W for the i7-875K versus 28 W for the i5-5257U, reflecting the desktop versus mobile design.

The process node is 45 nm for the i7-875K and 14 nm for the i5-5257U. Transistors are 774 million versus 1,900 million, and die size is 296 mm² versus 133 mm². The L3 cache is 8 MB shared versus 3 MB shared. Memory bandwidth is higher on the i5-5257U at 29.9 GB/s versus 21.3 GB/s, despite both using dual-channel DDR3. The PCIe lanes differ: the i7-875K has Gen 2 with 16 lanes, while the i5-5257U has Gen 2 with 12 lanes.

The i5-5257U includes integrated Intel Iris 6100 graphics, while the i7-875K has none. The i7-875K has an unlocked multiplier, while the i5-5257U is locked. The sockets are incompatible: LGA 1156 for the i7-875K and BGA 1168 for the i5-5257U. The launch MSRP for the i7-875K was $353, and for the i5-5257U it was $315. Both are end-of-life products, with release dates in May 2010 and February 2015 respectively.

FAQ

Q: Which CPU has more cores and threads?

A: The Intel Core i7-875K has 4 cores and 8 threads, while the Intel Core i5-5257U has 2 cores and 4 threads.

Q: Which processor wins in Cinebench multicore tests?

A: The Intel Core i7-875K wins all Cinebench multicore tests, with a 13.6% lead in cinebench_r15_multicore (275 vs 242) and a 13.5% lead in cinebench_r20_multicore (1146 vs 1010).

Q: How large is the single-core Geekbench gap?

A: The Intel Core i5-5257U scores 922 in geekbench_singlecore versus 499 for the Intel Core i7-875K, a 45.9% advantage.

Q: Do both CPUs support the same memory?

A: Both support DDR3 over a dual-channel bus, but the i5-5257U has higher bandwidth at 29.9 GB/s versus 21.3 GB/s for the i7-875K.

Q: Which CPU has integrated graphics?

A: Only the Intel Core i5-5257U has integrated graphics, specifically the Intel Iris 6100. The i7-875K has no integrated graphics.

Q: What is the TDP difference?

A: The Intel Core i7-875K has a TDP of 95 W, while the Intel Core i5-5257U has a TDP of 28 W.

The Verdict

The data supports two distinct user profiles. For anyone running heavily-threaded rendering workloads, the Intel Core i7-875K is the clear choice. It wins every Cinebench test by 13.4% to 13.6%, thanks to its 4 cores and 8 threads, and its higher boost clock of 3.60 GHz. Its 8 MB of L3 cache and 95 W TDP also indicate it is designed for sustained performance without thermal throttling.

For users prioritizing snappy single-threaded performance, the Intel Core i5-5257U is the better pick. Its 45.9% lead in geekbench_singlecore is overwhelming, and it even wins geekbench_multicore by 4.3% despite having half the cores. The 14 nm process and 1,900 million transistors deliver modern efficiency, and the integrated Iris 6100 graphics make it a complete package for a compact system.

The aggregate benchmarks are nearly tied—984 vs 976—but that obscures the functional reality. The i7-875K is a desktop workhorse for parallel tasks, while the i5-5257U is a mobile-efficient part that excels at the single-threaded tasks that dominate everyday computing. The i5-5257U’s 28 W TDP and smaller 133 mm² die also make it suitable for fanless or low-power designs, where the i7-875K’s 95 W TDP would be impractical. The choice is not about which is faster overall; it is about which workload matters more.