AMD Ryzen 5 PRO 7645 vs AMD Ryzen 7 PRO 8840U Comparison

The AMD Ryzen 5 PRO 7645 and AMD Ryzen 7 PRO 8840U are both Zen 4 parts, yet they serve almost opposing market segments: the former is a 65W desktop-class chip on Socket AM5, while the latter is a 28W mobile processor on Socket FP7. Despite the Ryzen 7's two extra cores, the benchmark data consistently favors the Ryzen 5 PRO 7645, which wins 15 of 17 head-to-head tests. However, the Ryzen 7 PRO 8840U reclaims ground in specific math workloads, making the choice between them a clear question of workload priority rather than raw core count.

Where Each One Wins

The AMD Ryzen 5 PRO 7645 is the decisive winner in rendering and general productivity. Across the entire Cinebench suite—R15, R20, and R23—it beats the Ryzen 7 PRO 8840U by a consistent 7.2% margin in both multi-core and single-core tests. For example, in Cinebench R23 multi-core, the 7645 scores 21710 against the 8840U's 20254. This pattern extends to PassMark's multithread test, where the 7645 posts 25489 versus 23850, a 6.9% advantage. The 7645 also dominates in physics simulation, scoring 1598 versus 1174—a massive 36.1% lead—and in prime number finding, where it scores 198 against the 8840U's 76, a 160.5% gap.

The Ryzen 7 PRO 8840U, however, is not without its strongholds. It wins two PassMark tests decisively: floating point math (50746 vs 45202, a 10.9% advantage) and integer math (88339 vs 74782, a 15.3% lead). These are heavy compute loops that scale with core count and raw execution resources, and the 8840U's 8 cores and 16 threads clearly pay off there. Beyond those two wins, the 8840U is also the more power-efficient option, with a 28W TDP compared to the 7645's 65W, making it the practical choice for battery-powered systems where sustained all-core loads are less common.

Architecture Differences

Both processors are built on AMD's Zen 4 architecture, but they diverge in nearly every physical aspect. The Ryzen 5 PRO 7645 uses the Raphael codename and is manufactured on TSMC's 5nm process node, while the Ryzen 7 PRO 8840U uses the Hawk Point codename and a more advanced 4nm node. This node difference is reflected in transistor counts: the 7645 packs 6,570 million transistors on a 71 mm² die, whereas the 8840U contains 25,000 million transistors on a 178 mm² die. The 8840U's larger die and transistor budget accommodate its 8 cores (16 threads) against the 7645's 6 cores (12 threads), plus a more capable integrated GPU.

Cache configurations also differ significantly. Both have 64 KB of L1 and 1 MB of L2 per core, but the shared L3 cache is halved on the mobile part: the 7645 has 32 MB shared L3, while the 8840U has only 16 MB shared L3. This is a critical structural difference—the desktop chip has more cache per core, which helps explain its single-core and gaming-like benchmark wins. Memory bandwidth is slightly higher on the 8840U at 89.6 GB/s versus 83.2 GB/s for the 7645, though both use dual-channel DDR5 and support ECC memory. PCIe support also differs: the 7645 offers Gen 5 with 24 CPU lanes, while the 8840U offers Gen 4 with 20 lanes, reflecting their desktop versus mobile positioning.

The integrated graphics are another major split. The 7645 includes basic "Radeon Graphics," while the 8840U features the Radeon 780M, a significantly beefier iGPU that is a key selling point for thin-and-light laptops. The sockets are incompatible: AM5 for the 7645 and FP7 for the 8840U. The 7645 is classified as Server/Workstation segment and released on 2023-06-12, while the 8840U is a Mobile part released on 2024-04-15. Neither has an unlocked multiplier, and both are currently Active in production.

Head-to-Head Benchmarks

The Cinebench results are remarkably uniform. The 7645 wins R15 multi-core with 2188 versus 2041 (7.2% delta), R15 single-core with 308 versus 288 (6.9%), R20 multi-core with 9118 versus 8506 (7.2%), R20 single-core with 1287 versus 1200 (7.3%), R23 multi-core with 21710 versus 20254 (7.2%), and R23 single-core with 3065 versus 2859 (7.2%). This consistency suggests the 7645's higher boost clock (5.10 GHz, same as the 8840U) combined with its larger L3 cache provides a per-thread advantage that the 8840U's extra cores cannot overcome in these heavily cache-sensitive workloads.

PassMark tests tell a more varied story. The 7645 wins data compression (286298 vs 272664, 5% delta), data encryption (16657 vs 16441, 1.3%), extended instructions (21813 vs 19132, 14%), find prime numbers (198 vs 76, 160.5%), multithread (25489 vs 23850, 6.9%), physics (1598 vs 1174, 36.1%), and random string sorting (34557 vs 33109, 4.4%). The single-thread scores are nearly identical at 3652 versus 3641 (0.3% delta), which aligns with the identical 5.10 GHz boost clock.

The 8840U's two wins are substantial. Floating point math at 50746 beats the 7645's 45202 by 10.9%, and integer math at 88339 beats 74782 by 15.3%. These are throughput-oriented tests that leverage all 8 cores and 16 threads efficiently, showing that when the workload is purely arithmetic and not constrained by cache or memory latency, the extra cores deliver a tangible advantage. The overall average benchmark scores are extremely close—32446 for the 7645 and 32233 for the 8840U, a 0.7% delta—placing both in the 83rd percentile of all CPUs.

FAQ

Q: Which processor is faster in Cinebench R23 multi-core?

A: The AMD Ryzen 5 PRO 7645 scores 21710, beating the AMD Ryzen 7 PRO 8840U's 20254 by 7.2%.

Q: Does the Ryzen 7 PRO 8840U win any benchmarks?

A: Yes, it wins two PassMark tests: floating point math (50746 vs 45202) and integer math (88339 vs 74782), with margins of 10.9% and 15.3% respectively.

Q: How do their single-thread performance compare?

A: They are nearly identical. The 7645 scores 3652 in PassMark single-thread versus the 8840U's 3641, a 0.3% delta. In Cinebench R23 single-core, the 7645 leads 3065 to 2859, a 7.2% advantage.

Q: What is the biggest performance gap between them?

A: The largest gap is in PassMark's find prime numbers test, where the 7645 scores 198 versus the 8840U's 76, a 160.5% difference.

Q: Which chip has more cores and threads?

A: The AMD Ryzen 7 PRO 8840U has 8 cores and 16 threads, while the AMD Ryzen 5 PRO 7645 has 6 cores and 12 threads.

Q: How do their cache sizes differ?

A: The 7645 has 32 MB of shared L3 cache, while the 8840U has only 16 MB. Both have 64 KB L1 and 1 MB L2 per core.

Specification Differences

| Field | AMD Ryzen 5 PRO 7645 | AMD Ryzen 7 PRO 8840U |

|-------|----------------------|------------------------|

| Series | 7000 series | 8000 series |

| Cores | 6 | 8 |

| Threads | 12 | 16 |

| Base Clock | 3.80 GHz | 3.30 GHz |

| Boost Clock | 5.10 GHz | 5.10 GHz |

| TDP | 65 W | 28 W |

| Socket | AMD Socket AM5 | AMD Socket FP7 |

| Codename | Raphael | Hawk Point |

| Process Node | 5 nm | 4 nm |

| Transistors | 6,570 million | 25,000 million |

| Die Size | 71 mm² | 178 mm² |

| L3 Cache | 32 MB (shared) | 16 MB (shared) |

| Memory Bandwidth | 83.2 GB/s | 89.6 GB/s |

| PCIe | Gen 5, 24 Lanes (CPU only) | Gen 4, 20 Lanes (CPU only) |

| Integrated Graphics | Radeon Graphics | Radeon 780M |

| Market Segment | Server/Workstation | Mobile |

| Release Date | 2023-06-12 | 2024-04-15 |