CPU Comparison

The Intel Core i7-940 and Intel Core i5-4258U represent two very different approaches to computing, separated by nearly five years of architectural evolution and targeting opposite ends of the performance spectrum. The data shows a surprisingly close overall contest despite their differences, with the i7-940 averaging a benchmark score of 903 against the i5-4258U’s 902, a razor-thin 0.1% margin. Yet the head-to-head results tell a more decisive story: the desktop Nehalem chip wins all five shared Cinebench tests, while the mobile Haswell part counters with additional Geekbench scores the i7-940 lacks entirely. Neither processor escapes the 24th percentile among all CPUs, placing both firmly in entry-level territory by modern standards. The i7-940 pairs 4 cores and 8 threads with a 2.93 GHz base and 3.20 GHz boost, while the i5-4258U makes do with 2 cores and 4 threads at 2.40 GHz base and 2.90 GHz boost. That core advantage translates directly into the benchmark results, but the i5-4258U’s 28W TDP versus the i7-940’s 130W TDP reveals a fundamental philosophy gap that no score can fully capture.

Head-to-Head Benchmarks

The Cinebench suite provides a clean, consistent picture: the Intel Core i7-940 wins every single shared test, and it does so with remarkable uniformity. In Cinebench R15 multicore, the i7-940 scores 264 against the i5-4258U’s 222, a 18.9% advantage. That lead barely moves in Cinebench R20 multicore, where 1102 versus 929 yields an 18.6% margin. The pattern holds through Cinebench R23 multicore at 2626 versus 2213, again 18.7% ahead. The single-core results are nearly identical in proportional terms: the i7-940 posts 155 in R20 single-core against 131, an 18.3% win, and 370 versus 312 in R23 single-core, an 18.6% win. The consistency is striking, across five tests, the deltaPct hovers between 18.3% and 18.9%, suggesting the i7-940’s extra cores and higher clocks deliver a predictable, repeatable performance edge.

The i5-4258U does have its own benchmark entries that the i7-940 cannot match, though they are not head-to-head comparisons. Its Geekbench multicore score of 1664 and single-core score of 844 appear in the FACT PACK, but no corresponding i7-940 numbers exist. This absence limits direct comparison, but the Cinebench data already establishes the hierarchy: the i7-940 wins all five shared tests, giving it a 5-0 record in the head-to-head breakdown. The average benchmark scores of 903 and 902 are effectively tied, which might suggest parity, but that aggregate hides the fact that the i5-4258U’s Geekbench results are included in its average while the i7-940’s are not. When both chips run the same workload, the older desktop part wins every time. The nearest rival data reinforces this: the two chips sit within 0.2% of each other in each other’s rival lists, with the i5-4258U trailing the i7-940 by 0.2% in the latter’s list and by 0.1% in its own.

FAQ

Q: Which processor is faster in multi-core workloads?

A: The Intel Core i7-940 wins every multi-core Cinebench test. It scores 264 versus 222 in R15, 1102 versus 929 in R20, and 2626 versus 2213 in R23, all roughly 18.6-18.9% ahead of the i5-4258U.

Q: Is the single-core performance difference similar to multi-core?

A: Yes, the margins are nearly identical. The i7-940 leads by 18.3% in R20 single-core (155 versus 131) and 18.6% in R23 single-core (370 versus 312), matching its multi-core advantage almost exactly.

Q: Do these CPUs have integrated graphics?

A: Only the Intel Core i5-4258U has integrated graphics, specifically Intel HD 5100. The i7-940 has no integrated graphics listed, meaning it requires a discrete GPU for any display output.

Q: What are the core and thread counts?

A: The i7-940 has 4 cores and 8 threads, while the i5-4258U has 2 cores and 4 threads. The i7-940’s thread count is double its core count via Hyper-Threading, and the i5-4258U similarly doubles its 2 cores to 4 threads.

Q: How do their TDPs compare?

A: The i7-940 has a TDP of 130W, while the i5-4258U draws only 28W. That is a 102W difference, making the i5-4258U dramatically more power-efficient despite its lower performance.

Q: Which CPU has the higher boost clock?

A: The i7-940 boosts to 3.20 GHz, which is 0.30 GHz higher than the i5-4258U’s 2.90 GHz boost. Its base clock of 2.93 GHz is also higher than the i5’s 2.40 GHz base.

Architecture Differences

The architectural gap between these two chips is enormous, reflecting a five-year evolution in Intel’s design philosophy. The i7-940 uses the Nehalem architecture on the Bloomfield codename, built on a 45 nm process at Intel’s foundry. It packs 731 million transistors into a 263 mm² die. In contrast, the i5-4258U uses Haswell architecture with the same Haswell codename, fabricated on a 22 nm process, also at Intel. It contains 1,400 million transistors, nearly double the i7-940, but on a much smaller 118 mm² die. The 22 nm node allows far greater transistor density, which explains how Haswell fits more transistors into less than half the silicon area.

Cache hierarchies differ as well. Both share the same L1 and L2 configurations: 64 KB of L1 per core and 256 KB of L2 per core. The divergence appears at L3, where the i7-940 offers 8 MB of shared cache versus the i5-4258U’s 3 MB. That 5 MB difference matters for workloads that repeatedly access large datasets. Memory support also splits: the i7-940 uses DDR3 with triple-channel memory access, while the i5-4258U also supports DDR3 but has no memory bus specification listed. The i7-940’s triple-channel setup provides a theoretical bandwidth advantage, though no concrete bandwidth figures appear in the data. PCIe support is another differentiator, the i7-940 lists Gen 2 PCIe, while the i5-4258U has no PCIe specification at all, reflecting its mobile BGA 1168 socket versus the i7-940’s desktop Socket 1366.

The i5-4258U includes Intel HD 5100 integrated graphics, a feature entirely absent from the i7-940. This makes the mobile chip a complete system-on-chip solution, capable of driving displays without additional hardware. The i7-940 requires a separate graphics card. Both processors are locked (multiplierUnlocked is false), so neither offers overclocking headroom. The i7-940’s part number is SLBCK, while the i5-4258U’s is SR18A. Release dates differ by about four and a half years: the i7-940 launched on November 16, 2008, and the i5-4258U on June 3, 2013.

The Verdict

The choice between these two processors depends entirely on the use case, and the data supports a clear split. For raw computing performance, the Intel Core i7-940 is the unambiguous winner. It outperforms the i5-4258U by roughly 18.5% across all five shared Cinebench tests, whether single-core or multi-core. Its 4 cores and 8 threads provide double the parallel processing capacity of the i5-4258U’s 2 cores and 4 threads. The 8 MB of L3 cache versus 3 MB further favors the desktop chip. If the task is CPU-bound and performance is the only criterion, the i7-940 is the better choice, provided the system can handle its 130W TDP and lacks integrated graphics.

The i5-4258U wins on efficiency and integration. Its 28W TDP is less than a quarter of the i7-940’s 130W, making it suitable for compact or battery-powered systems. The integrated Intel HD 5100 graphics eliminate the need for a discrete GPU, which the i7-940 cannot do. The newer 22 nm process and 1,400 million transistors in a smaller die indicate a more modern design, even if the benchmark scores do not reflect a performance advantage. For a laptop or a low-power mini PC, the i5-4258U is the only viable option of the two. The i7-940 is end-of-life and requires a desktop Socket 1366 motherboard, while the i5-4258U’s production status is not listed, suggesting it may still be available. Neither chip exceeds the 24th percentile among all CPUs, so buyers should not expect competitive modern performance from either.

Specification Differences

The two processors differ in nearly every major specification category. The i7-940 has 4 cores and 8 threads; the i5-4258U has 2 cores and 4 threads. The i7-940 runs at 2.93 GHz base and 3.20 GHz boost; the i5-4258U runs at 2.40 GHz base and 2.90 GHz boost. TDP is a massive divergence: 130W for the i7-940 versus 28W for the i5-4258U. The i7-940 uses Intel Socket 1366, while the i5-4258U uses Intel BGA 1168. Architecture differs from Nehalem (Bloomfield) to Haswell (Haswell), with process nodes of 45 nm versus 22 nm. Transistor counts are 731 million versus 1,400 million, and die sizes are 263 mm² versus 118 mm².

L3 cache is 8 MB shared on the i7-940 versus 3 MB shared on the i5-4258U. Memory support is DDR3 for both, but the i7-940 offers triple-channel memory bus while the i5-4258U has no memory bus listed. The i7-940 supports Gen 2 PCIe; the i5-4258U has no PCIe specification. Integrated graphics appear only on the i5-4258U as Intel HD 5100. The i7-940 targets the desktop market segment and is end-of-life; the i5-4258U targets mobile with no production status given. Release dates are November 16, 2008 for the i7-940 and June 3, 2013 for the i5-4258U. Part numbers are SLBCK and SR18A respectively. Both have locked multipliers. Neither supports ECC memory.

Where Each One Wins

The Intel Core i7-940 wins in every measured performance category. It takes all five head-to-head Cinebench tests, with wins ranging from 18.3% to 18.9%. Its 8 MB of L3 cache and 4-core/8-thread configuration give it a clear edge in multi-threaded applications like video rendering, compilation, or any workload that scales with thread count. The higher base and boost clocks (2.93 GHz and 3.20 GHz versus 2.40 GHz and 2.90 GHz) contribute to its single-core wins as well. The triple-channel memory bus provides a theoretical bandwidth advantage over the i5-4258U’s unspecified memory configuration, which could benefit memory-intensive tasks. For anyone building a desktop system where power consumption is not a concern and a discrete GPU is already planned, the i7-940 is the superior processor.

The Intel Core i5-4258U wins in efficiency and integration. Its 28W TDP makes it suitable for laptops, ultrabooks, or fanless designs where the i7-940’s 130W would be impractical. The integrated Intel HD 5100 graphics means the i5-4258U can function as a complete platform without additional hardware, whereas the i7-940 requires a separate graphics card. The newer 22 nm process and smaller die size (118 mm² versus 263 mm²) indicate lower manufacturing costs and better thermal characteristics, even though those are not directly benchmarked. The i5-4258U also has Geekbench scores (1664 multi-core, 844 single-core) that the i7-940 lacks entirely, suggesting the mobile chip has been tested in a wider range of scenarios. For mobile use or low-power desktop builds, the i5-4258U is the only sensible pick. The i7-940’s end-of-life status and desktop-only socket further limit its appeal outside traditional tower systems.