AMD Ryzen 7 3800X vs AMD Ryzen 7 7840H Comparison

The Verdict

The data presents an unusually decisive generational sweep. The AMD Ryzen 7 7840H wins 16 of the 17 head-to-head benchmarks against the AMD Ryzen 7 3800X, with the only loss coming in a single niche test. Despite the 3800X being a desktop part with a 105 W TDP and the 7840H being a mobile part with a 35 W TDP, the newer Zen 4 architecture delivers superior performance across nearly every measurable workload.

The 7840H is the clear choice for any workload where single-threaded responsiveness, multi-core throughput, or floating-point math matters. Its 21.2% advantage across all Cinebench R15, R20, and R23 tests—both single-core and multi-core—is remarkably consistent, indicating a pure architectural generational gain rather than workload-specific optimization. The 3800X retains a single advantage in prime number finding, where it scores 103 versus 83, a 19.4% edge, but this is an outlier against an otherwise uniform defeat.

For a user prioritizing the legacy desktop platform with its unlocked multiplier and higher base clock, the 3800X has niche appeal. However, the benchmark data shows that the 7840H, despite being designed for mobile, outperforms the older desktop chip by 21.1% in PassMark multithread and 34.3% in single-thread tests. The verdict is unambiguous: the 7840H is the superior processor in almost every measurable way, and the 3800X is only relevant for those specifically needing the AM4 socket or the unlocked multiplier.

Architecture Differences

The two processors represent two distinct generations of AMD design philosophy. The 7840H is built on the Zen 4 architecture with the Phoenix codename, fabricated on a 4 nm TSMC process. Its transistor count is listed at 25,000 million across a 178 mm² die. In contrast, the 3800X uses the Zen 2 architecture with the Matisse codename, on a 7 nm TSMC process, with 3,800 million transistors on a 74 mm² die. The process node shrink from 7 nm to 4 nm and the correspondingly higher transistor density explain much of the performance differential.

The 7840H features 8 cores and 16 threads, with a base clock of 3.80 GHz and a boost clock of 5.10 GHz. The 3800X also has 8 cores and 16 threads, with a base clock of 3.90 GHz and a boost clock of 4.50 GHz. Despite the 3800X starting at a 100 MHz higher base clock, the 7840H's 600 MHz higher boost clock and superior IPC from Zen 4 allow it to dominate.

Cache configurations differ significantly. The 7840H has 64 KB of L1 per core, 1 MB of L2 per core, and 16 MB of shared L3 cache. The 3800X also has 64 KB of L1 per core but only 512 KB of L2 per core, and a larger 32 MB of shared L3 cache. The 7840H's doubled L2 cache per core likely contributes to its single-threaded advantage, despite the 3800X having twice the total L3 capacity.

Memory support is another fundamental divergence. The 7840H supports DDR5 memory with a dual-channel bus and a memory bandwidth of 89.6 GB/s, while the 3800X supports DDR4 with a dual-channel bus and 51.2 GB/s bandwidth. The 7840H also supports ECC memory, whereas the 3800X does not. The 7840H's 75% higher memory bandwidth directly benefits memory-sensitive workloads.

The 7840H integrates a Radeon 780M graphics unit, while the 3800X has no integrated graphics. The 7840H has 20 PCIe Gen 4 lanes, while the 3800X has 24 PCIe Gen 4 lanes. The 7840H is a mobile part on the AMD Socket FP8, while the 3800X is a desktop part on the AM4 socket. The 3800X's multiplier is unlocked for overclocking, while the 7840H's is locked. The 3800X was released on July 6, 2019, while the 7840H's release date is not listed.

Head-to-Head Benchmarks

The most striking result is the uniform 21.2% advantage for the 7840H across all six Cinebench tests. In Cinebench R23 multicore, the 7840H scores 23,731 against the 3800X's 19,588. In single-core R23, the scores are 3,350 versus 2,765. This consistency suggests a fundamental IPC improvement rather than any scaling quirk. The R15, R20, and R23 results all show the same 21.2% delta, which is unusual and indicates a clean architectural lead.

The floating-point math test shows the largest single delta. The 7840H scores 58,724 in PassMark floating-point math, against 39,759 for the 3800X—a 47.7% advantage. This is nearly double the Cinebench margin and suggests the Zen 4 execution units are substantially wider or more efficient for FP workloads. Integer math also shows a massive 42.8% gap, with 96,692 versus 67,725.

Single-threaded performance is where the 7840H shines in a way typical of a newer architecture. In PassMark single-thread, the 7840H scores 3,641 versus 2,712, a 34.3% advantage. This aligns with the 600 MHz boost clock advantage and the IPC improvements from Zen 4. Extended instructions show a 28% lead for the 7840H (25,654 versus 20,037), indicating better SIMD execution.

The multithread PassMark score shows a 21.1% lead (27,919 versus 23,046), which is consistent with the Cinebench results. Data compression shows a 12% lead (341,520 versus 304,853), while data encryption shows a narrower 4.3% lead (20,162 versus 19,337). Random string sorting shows an 18.5% lead (38,938 versus 32,869). Physics simulation shows a modest 6.1% lead (1,301 versus 1,226).

The single loss for the 3800X comes in PassMark's find prime numbers test, where it scores 103 against the 7840H's 83—a 19.4% advantage. This is a peculiar result, as the 3800X's larger 32 MB L3 cache may benefit this specific workload, which often relies on large lookup tables. It is the only test where the older chip wins, and it is not a typical representative of general computing workloads.

Specification Differences

The two processors differ in nearly every specification field. The 7840H has a base clock of 3.80 GHz versus 3.90 GHz for the 3800X. The boost clock favors the 7840H at 5.10 GHz versus 4.50 GHz. TDP is dramatically different: 35 W for the 7840H versus 105 W for the 3800X. The 7840H uses the AMD Socket FP8, while the 3800X uses the AM4 socket.

The cache hierarchy differs in L2 and L3. The 7840H has 1 MB L2 per core while the 3800X has 512 KB L2 per core. The L3 cache is 16 MB shared on the 7840H versus 32 MB on the 3800X. Memory support is DDR5 for the 7840H versus DDR4 for the 3800X. Memory bandwidth is 89.6 GB/s versus 51.2 GB/s. ECC memory is supported on the 7840H but not the 3800X.

The 7840H has an integrated Radeon 780M GPU, while the 3800X has none. The 7840H has 20 PCIe Gen 4 lanes, while the 3800X has 24. The 7840H's multiplier is locked; the 3800X's is unlocked. The market segment is mobile for the 7840H and desktop for the 3800X. The 7840H has a listed part number of 100-000000955(FP7r2), 100-000000964(FP7), and 100-000001129(FP8), while the 3800X's part number is 100-000000025. The 3800X has a launch MSRP of $399.

FAQ

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

A: The AMD Ryzen 7 7840H wins all multi-core tests. In Cinebench R23 multicore, it scores 23,731 versus 19,588 for the 3800X, a 21.2% advantage. PassMark multithread shows 27,919 versus 23,046, a 21.1% lead.

Q: How do they compare in single-threaded performance?

A: The 7840H leads by 34.3% in PassMark single-thread, scoring 3,641 versus 2,712. In Cinebench R23 single-core, the scores are 3,350 versus 2,765, also a 21.2% delta.

Q: Does the 3800X win any benchmark?

A: Yes, the 3800X wins the PassMark find prime numbers test, scoring 103 versus 83 for the 7840H, a 19.4% advantage. This is the only test it wins out of 17 head-to-head comparisons.

Q: What is the TDP difference between the two?

A: The 7840H has a TDP of 35 W, while the 3800X has a TDP of 105 W. Despite the much lower power envelope, the 7840H outperforms the 3800X in 16 of 17 benchmarks.

Q: Which processor supports faster memory?

A: The 7840H supports DDR5 with a memory bandwidth of 89.6 GB/s, while the 3800X supports DDR4 with 51.2 GB/s. The 7840H also supports ECC memory, which the 3800X does not.

Q: What is the core and thread count for each?

A: Both processors have 8 cores and 16 threads. The difference lies in the architecture: the 7840H uses Zen 4 (Phoenix) while the 3800X uses Zen 2 (Matisse).