Intel Core i7-5820K vs Intel Core i7-7740X Comparison

The data presents an unusual generational matchup. The Intel Core i7-7740X is a modern 7th Gen Kaby Lake-X part, while the Intel Core i7-5820K is an older 5th Gen Haswell-E processor. Despite the age gap, the benchmark results show they are extremely close overall. The i7-5820K wins seven of eight head-to-head tests, while the i7-7740X takes a single, decisive victory in Geekbench single-core. This split makes the choice between them entirely dependent on the specific workload.

Where Each One Wins

The Intel Core i7-5820K is the consistent winner in multi-threaded and most single-threaded legacy benchmarks. It holds a lead in every Cinebench test (R15, R20, R23) for both multi-core and single-core, as well as in Geekbench multi-core. This dominance is driven by its two extra physical cores and four additional threads, which provide a substantial advantage in heavily parallel tasks like video rendering, 3D modeling, and code compilation. Its victory in Cinebench single-core, albeit by a narrow margin, indicates its architecture scales efficiently even when only one core is active.

The Intel Core i7-7740X wins only in Geekbench single-core, and it wins spectacularly. The score of 1619 versus 1174 represents a 37.9% advantage. This is a massive gap that points to the newer Kaby Lake architecture’s superior per-core instructions-per-clock (IPC) and much higher clock speeds. This makes the 7740X the clear choice for lightly threaded applications that are sensitive to single-thread performance, such as older games, certain simulation software, and some productivity tools that haven't been optimized for many cores.

For everything else, the 5820K is the default pick. The data shows it is not just a multi-core specialist; it also edges out the 7740X in single-core Cinebench tests, meaning the 5820K’s six cores do not hold it back in these specific workloads. The 7740X’s single win is a stark outlier, making it a specialist part for a specific type of workload.

Architecture Differences

The two CPUs are built on fundamentally different designs. The i7-7740X uses the Kaby Lake architecture on a 14 nm process node, while the i7-5820K uses the older Haswell architecture on a 22 nm process node. This process shrink is a key reason for the 7740X’s efficiency and higher clock speeds.

The core configurations differ significantly. The 7740X has 4 cores and 8 threads, while the 5820K has 6 cores and 12 threads. This 50% core advantage for the 5820K is its primary weapon in multi-threaded tests. The cache hierarchy also differs. The 7740X has a shared 8 MB L3 cache, while the 5820K has a shared 15 MB L3 cache. The larger cache on the 5820K helps feed its additional cores.

The platforms are entirely different. The 7740X uses the Intel Socket 2066, while the 5820K uses the Intel Socket 2011-3. The 5820K’s specification explicitly lists its PCIe support as Gen 3 with 28 lanes (CPU only). The 7740X is listed simply as Gen 3. Both support DDR4 memory and feature a quad-channel memory bus. The 5820K has a listed memory bandwidth of 68.3 GB/s, a figure not provided for the 7740X.

The process node difference also impacts power. The 7740X has a TDP of 112, while the 5820K has a TDP of 140. The 5820K also has a listed transistor count of 2,600 million on a 356 mm² die, whereas no such figures are in the pack for the 7740X. The 5820K is designated as end-of-life, while the 7740X is marked as active production. Both have unlocked multipliers for overclocking.

Head-to-Head Benchmarks

The benchmark results paint a clear picture of consistent, though often narrow, superiority for the i7-5820K. In Cinebench R15 multi-core, the 5820K scores 841 against the 7740X’s 831, a 1.2% lead. The single-core R15 result is nearly identical, with the 5820K winning 118 to 117, a 0.8% difference. This pattern repeats in Cinebench R20, where the 5820K wins multi-core 3508 to 3465 (1.2%) and single-core 495 to 488 (1.4%).

The Cinebench R23 results show the same trend. The 5820K wins multi-core with a score of 8354 compared to 8250, a 1.2% lead. In single-core, it wins 1179 to 1164, a 1.3% margin. These Cinebench results indicate that despite the 7740X’s newer architecture and higher clocks, the 5820K’s extra cores and larger cache provide a tangible, albeit small, advantage in rendering workloads, even when only one core is utilized.

The Geekbench multi-core test shows a larger gap. The 5820K scores 5464 against the 7740X’s 5246, a 4% advantage. This is the biggest win for the 5820K and suggests Geekbench’s multi-core workload scales well with the 5820K’s six cores.

The single outlier is Geekbench single-core. The 7740X scores 1619, while the 5820K scores 1174. This yields a 37.9% difference in favor of the 7740X. This is a dramatic reversal. The newer Kaby Lake core, combined with a 4.30 GHz base and 4.60 GHz boost clock, dominates the older Haswell core in this specific test.

Specification Differences

The specification sheets reveal the key architectural gaps. The most obvious difference is core count: the i7-7740X has 4 cores and 8 threads, whereas the i7-5820K has 6 cores and 12 threads. The clock speeds are inverted, with the 7740X running at 4.30 GHz base and 4.60 GHz boost, while the 5820K runs at 3.30 GHz base and 3.60 GHz boost.

The process node is a major differentiator, with the 7740X on 14 nm and the 5820K on 22 nm. The L3 cache is also different: 8 MB shared on the 7740X versus 15 MB shared on the 5820K. The memory bandwidth is listed as 68.3 GB/s for the 5820K, with no figure given for the 7740X.

The sockets are incompatible: Socket 2066 for the 7740X and Socket 2011-3 for the 5820K. The TDPs are 112 for the 7740X and 140 for the 5820K. The 5820K has a specified transistor count of 2,600 million and a die size of 356 mm², while the 7740X does not list these. The production status differs, with the 7740X active and the 5820K end-of-life. The release dates are also distinct, with the 7740X launching in 2017-06-25 and the 5820K in 2014-08-31. The 5820K has a part number of SR20S, which the 7740X lacks.

FAQ

Q: Which CPU is faster in multi-core performance?

A: The Intel Core i7-5820K wins in all multi-core tests. It scores 841 vs 831 in Cinebench R15, 3508 vs 3465 in R20, 8354 vs 8250 in R23, and 5464 vs 5246 in Geekbench multi-core.

Q: Is the newer i7-7740X better for single-core tasks?

A: It depends on the benchmark. The 7740X wins Geekbench single-core by a huge margin, scoring 1619 vs 1174 (37.9% ahead). However, the 5820K wins Cinebench single-core tests, including R15 (118 vs 117), R20 (495 vs 488), and R23 (1179 vs 1164).

Q: How many cores and threads does each processor have?

A: The i7-7740X has 4 cores and 8 threads. The i7-5820K has 6 cores and 12 threads.

Q: What are the process node sizes for these CPUs?

A: The i7-7740X is built on a 14 nm process, while the i7-5820K uses a 22 nm process node.

Q: Do they use the same motherboard socket?

A: No. The i7-7740X uses Intel Socket 2066, and the i7-5820K uses Intel Socket 2011-3.

Q: Which processor has a higher base clock speed?

A: The i7-7740X has a base clock of 4.30 GHz, which is higher than the i7-5820K’s 3.30 GHz base clock.

The Verdict

The data dictates a clear split decision. For users whose primary workloads are multi-threaded, such as video editing, 3D rendering, or running virtual machines, the Intel Core i7-5820K is the superior choice. It demonstrates a lead in every Cinebench multi-core test and a 4% advantage in Geekbench multi-core. The two additional cores and 15 MB of L3 cache provide a measurable benefit that the 7740X cannot overcome, despite its architectural advantages.

However, there is a specific scenario where the i7-7740X is the clear winner. The 37.9% margin in Geekbench single-core is a massive indicator of raw per-core power. Any application that relies almost exclusively on a single thread will see a dramatic performance boost on the 7740X. This includes many legacy games, certain scientific applications, and specific scripting workloads.

The overall average benchmark scores are nearly identical, with the 7740X at 2648 and the 5820K at 2642, a 0.2% difference. This places them in the 50th and 49th percentiles of all CPUs, respectively. The decision ultimately comes down to workload. The 5820K is the all-around workhorse, winning the majority of tests. The 7740X is a specialist, offering exceptional performance in a narrow but important niche of single-threaded applications. A buyer must assess whether that single, massive Geekbench win is worth sacrificing the consistent, broad-based performance of the 5820K.