AMD Ryzen 5 8645HS vs AMD Ryzen 7 7800X3D Comparison

The AMD Ryzen 5 8645HS and AMD Ryzen 7 7800X3D represent two distinct philosophies within AMD’s Zen 4 lineup: one is a 6-core mobile processor built for efficiency, and the other is an 8-core desktop chip with a massive cache. The benchmark data shows a clear performance hierarchy, but the choice between them depends entirely on the target platform and workload. The Ryzen 7 7800X3D wins 14 of the 15 head-to-head comparisons, often by substantial margins, while the Ryzen 5 8645HS edges out a single victory in one Cinebench R23 single-core test.

FAQ

Q: Which processor has the higher boost clock?

A: Both processors share the same maximum boost clock of 5.00 GHz, making their single-core potential nominally identical.

Q: How much larger is the L3 cache on the Ryzen 7 7800X3D?

A: The Ryzen 7 7800X3D has 96 MB of shared L3 cache, which is 80 MB more than the 16 MB shared L3 cache found on the Ryzen 5 8645HS.

Q: What are the core and thread counts for each CPU?

A: The Ryzen 5 8645HS has 6 cores and 12 threads, while the Ryzen 7 7800X3D has 8 cores and 16 threads.

Q: In which benchmark does the Ryzen 5 8645HS outperform the Ryzen 7 7800X3D?

A: The Ryzen 5 8645HS wins the Cinebench R23 single-core test with a score of 1714, compared to the Ryzen 7 7800X3D’s 1713, a margin of 0.1%.

Q: Which CPU has the higher TDP?

A: The Ryzen 7 7800X3D has a TDP of 120 watts, while the Ryzen 5 8645HS has a TDP of 45 watts.

Q: What are the memory bandwidth specifications for each processor?

A: The Ryzen 5 8645HS supports a memory bandwidth of 89.6 GB/s, whereas the Ryzen 7 7800X3D supports 83.2 GB/s.

The Verdict

The data points to a straightforward conclusion for desktop builders: the AMD Ryzen 7 7800X3D is the superior performer in nearly every metric. Its 8-core configuration, combined with a 96 MB L3 cache, delivers decisive wins in multi-threaded and cache-sensitive workloads. The Ryzen 5 8645HS, in contrast, is a mobile chip designed for a different environment. Its lower TDP and smaller footprint make it suitable for laptops, but its benchmark scores lag significantly. For anyone assembling a desktop PC with an AM5 socket, the Ryzen 7 7800X3D is the clear choice. The Ryzen 5 8645HS only makes sense in a mobile context where its power envelope is a necessity, but even then, its single-core advantage over the 7800X3D is negligible at 0.1%.

Head-to-Head Benchmarks

The most striking disparity appears in the Cinebench R15 multicore test, where the Ryzen 7 7800X3D scores 2878.5 against the Ryzen 5 8645HS’s 2094. That is a 27.3% lead for the desktop chip. The pattern continues in Cinebench R23 multicore, where the 7800X3D’s 16817 score outpaces the 8645HS’s 13220 by 21.4%. These multi-threaded results reflect the two extra cores and four extra threads available to the 7800X3D.

The single-core picture is nearly identical. In Cinebench R15 single-core, the 7800X3D wins with 281.5 versus 270, a 4.1% lead. The only flip occurs in Cinebench R23 single-core, where the 8645HS scores 1714 against the 7800X3D’s 1713, a razor-thin 0.1% edge. This negligible difference suggests that per-core architecture is effectively tied, with the 8645HS holding a marginal frequency or efficiency advantage.

PassMark’s integer math test shows a 29.9% advantage for the 7800X3D, scoring 103639 versus 72640. Floating point math follows suit, with the 7800X3D at 61187 compared to 44833, a 26.7% lead. The largest percentage gap appears in the prime number finding test: the 7800X3D scores 324, while the 8645HS manages only 75, a crushing 76.9% deficit for the mobile chip. This test highlights the impact of the larger cache and additional cores on algorithmic workloads.

Data compression and encryption follow the expected trend. The 7800X3D scores 384669 in data compression, 31% higher than the 8645HS’s 265483. Encryption shows a 30.2% gap, with scores of 22346 and 15588, respectively. The multithreaded PassMark score widens to a 34.1% difference, as the 7800X3D hits 34293 against 22586.

The 7800X3D also dominates in the physics simulation test, scoring 3522 versus 1095, a 68.9% margin. Random string sorting shows a 30.1% lead for the desktop chip, with 45418 against 31748. Even in single-threaded PassMark tests, the 7800X3D maintains a 2.8% edge, scoring 3759 versus 3653.

Specification Differences

The two processors differ across several fundamental specifications. The Ryzen 5 8645HS has 6 cores and 12 threads, while the Ryzen 7 7800X3D has 8 cores and 16 threads. Base clocks diverge slightly: the 8645HS runs at 4.30 GHz, and the 7800X3D at 4.20 GHz, though both boost to 5.00 GHz. TDP is a major separator, with the 8645HS rated at 45 watts and the 7800X3D at 120 watts.

The memory bandwidth is higher on the mobile chip at 89.6 GB/s versus 83.2 GB/s for the desktop part. ECC memory support is another differentiator: the 7800X3D supports ECC, while the 8645HS does not. PCIe capabilities also differ, with the 8645HS offering Gen 4 with 20 lanes (CPU only) and the 7800X3D providing Gen 5 with 24 lanes (CPU only). The integrated graphics are listed as Radeon 760M for the 8645HS and Radeon Graphics for the 7800X3D. The 8645HS targets the mobile segment on the AMD Socket FP8, while the 7800X3D is a desktop chip on the AMD Socket AM5.

Architecture Differences

Both processors are built on AMD’s Zen 4 architecture, but they use different process nodes and package designs. The Ryzen 5 8645HS uses TSMC’s 4 nm process and is part of the Hawk Point codename family, with a die size of 178 mm² and 25,000 million transistors. The Ryzen 7 7800X3D is manufactured on TSMC’s 5 nm process, belongs to the Raphael codename family, and has a die size of 71 mm² with 11,270 million transistors. The 7800X3D’s smaller die and lower transistor count reflect its chiplet-based desktop design, whereas the 8645HS is a monolithic mobile chip.

Cache differences are the most architecturally significant. Both have 64 KB of L1 cache per core and 1 MB of L2 cache per core. However, the shared L3 cache is vastly different: the 8645HS has 16 MB, while the 7800X3D has 96 MB. This 3D V-Cache technology is the defining feature of the 7800X3D, providing a substantial advantage in cache-sensitive workloads. The 8645HS has no V-Cache equivalent. Both support dual-channel DDR5 memory, but the 8645HS offers slightly higher bandwidth at 89.6 GB/s.

Where Each One Wins

The Ryzen 7 7800X3D is the winner in almost every conceivable desktop workload. Its 8-core, 16-thread configuration delivers a 21.4% lead in Cinebench R23 multicore and a 34.1% lead in PassMark multithread. The 96 MB L3 cache provides a massive boost in cache-heavy tasks like prime number finding, where it leads by 76.9%, and physics simulation, where it leads by 68.9%. For gaming, content creation, and productivity, the 7800X3D’s raw throughput is unmatched by the 8645HS. The 7800X3D also holds a smaller but consistent edge in single-threaded PassMark tests, scoring 2.8% higher.

The Ryzen 5 8645HS’s only victory is a single Cinebench R23 single-core run, where it scores 1714 versus 1713. This 0.1% margin is statistically insignificant, but it does show that the mobile chip’s Zen 4 cores are not inferior on a per-thread basis. The 8645HS also has a lower TDP of 45 watts, making it the only viable option for thin-and-light laptops. Its higher memory bandwidth of 89.6 GB/s is a minor advantage, but it does not translate into benchmark wins. The 8645HS’s integrated Radeon 760M graphics may be more capable than the 7800X3D’s generic Radeon Graphics, but the data does not include graphics benchmarks. Ultimately, the 8645HS wins only where the 7800X3D cannot be used: in a mobile form factor requiring a 45-watt envelope.