AMD Ryzen 9 3900 vs AMD Ryzen 9 PRO 5945 Comparison

The data is unambiguous: the AMD Ryzen 9 PRO 5945 is the faster processor in nearly every measurable workload, but the AMD Ryzen 9 3900 remains a relevant contender with specific strengths. The benchmark results show a clear generational shift, with the PRO 5945 winning 11 of the 13 head-to-head comparisons, while the 3900 manages only 2 victories. However, the magnitude of the wins varies dramatically across workloads, and the architecture differences explain why.

Head-to-Head Benchmarks

The most decisive victory for the AMD Ryzen 9 PRO 5945 comes in single-core performance, where the gap is nothing short of massive. In Cinebench R15 single-core, the PRO 5945 scores 417 against the 3900’s 197, a 52.8% advantage. This is not an incremental improvement; it represents a fundamental leap in per-thread efficiency. The PassMark single-thread test confirms the trend, with the PRO 5945 posting 3499 versus 2604 for the 3900, a 25.6% lead. This pattern holds in multi-core tests, though the margins are smaller. In Cinebench R15 multi-core, the PRO 5945 scores 2959 against 2804, a 5.2% edge, while PassMark multithread shows 34549 against 30586, an 11.5% advantage.

The PRO 5945’s dominance extends into compute-heavy integer and floating-point workloads. PassMark integer math shows the PRO 5945 at 129768, a full 24.7% ahead of the 3900’s 97698. Floating-point math is similarly lopsided: 70291 for the PRO 5945 versus 56730 for the 3900, a 19.3% margin. Even in prime number finding, the PRO 5945 leads with 228 against 203, an 11% difference. Physics simulation favors the PRO 5945 as well, with 1772 versus 1617, an 8.7% edge.

The AMD Ryzen 9 3900’s two wins are narrower but still noteworthy. In data encryption, the 3900 scores 26657 against the PRO 5945’s 26313, a 1.3% advantage. In random string sorting, the 3900 posts 44902 versus 43447, a 3.3% lead. These are the only areas where the older chip manages to outpace its successor, and the margins are modest. Data compression is effectively a tie, with the PRO 5945 at 416599 against the 3900’s 413887, a 0.7% difference that is within noise. Extended instructions also favor the PRO 5945, but only by 3.5%, with scores of 27031 and 26073 respectively.

Where Each One Wins

The AMD Ryzen 9 PRO 5945 is the clear winner for any workload that benefits from modern single-thread performance or heavy parallel compute. Its 25.6% lead in single-thread benchmarks makes it the superior choice for everyday responsiveness, lightly-threaded applications, and legacy software that relies on one or two cores. The 24.7% advantage in integer math and 19.3% lead in floating-point math position it as the better option for scientific computing, financial modeling, and any task that involves heavy arithmetic. The 11.5% multithread lead and 8.7% physics advantage further cement its status for rendering, video encoding, and simulation workloads.

The AMD Ryzen 9 3900 wins in two specific, narrow niches. Its 1.3% advantage in data encryption suggests it handles certain cryptographic workloads slightly better, though the margin is small enough that real-world differences would be imperceptible. The 3.3% lead in random string sorting indicates a minor edge in specific data-manipulation tasks, possibly related to memory access patterns or cache behavior. Neither of these wins is large enough to recommend the 3900 over the PRO 5945 for any general-purpose use case, but they do show that the older architecture is not completely obsolete.

Architecture Differences

The two processors represent two distinct generations of AMD’s Zen architecture. The AMD Ryzen 9 3900 is built on Zen 2, with the codename Matisse, while the AMD Ryzen 9 PRO 5945 uses Zen 3, codenamed Vermeer. Both are manufactured on TSMC’s 7 nm process node, and both use a dual-chiplet design with a die size of 2x 74 mm². The transistor count differs, however: the 3900 packs 7,600 million transistors, while the PRO 5945 has 8,300 million, a 9.2% increase that reflects the architectural improvements.

The cache hierarchy is identical between the two: 64 KB of L1 per core, 512 KB of L2 per core, and 64 MB of L3 total. This means the performance differences are not explained by cache capacity but by the efficiency of the cores themselves. Zen 3 introduced a unified 8-core complex (CCX) design, which reduces latency between cores and improves inter-core communication. This architectural change is the primary driver behind the PRO 5945’s significant single-core and multi-core performance advantages, particularly the 52.8% lead in Cinebench R15 single-core.

The fact that the PRO 5945 achieves its performance with a lower base clock (3.00 GHz versus 3.10 GHz) but a much higher boost clock (4.70 GHz versus 4.30 GHz) shows that Zen 3 is fundamentally more efficient per clock. The PRO 5945 also features a locked multiplier, while the 3900 has an unlocked multiplier, meaning overclocking is only possible on the older chip. Both processors support DDR4 memory on a dual-channel bus with 51.2 GB/s bandwidth, and both lack integrated graphics. The 3900 offers 24 PCIe Gen 4 lanes, while the PRO 5945 offers 20, a difference that matters for users with multiple high-speed storage devices or expansion cards.

Specification Differences

The most significant specification difference is the architecture: Zen 2 for the 3900 versus Zen 3 for the PRO 5945. This drives all other performance-related differences. The base clock is slightly higher on the 3900 (3.10 GHz versus 3.00 GHz), but the boost clock is significantly higher on the PRO 5945 (4.70 GHz versus 4.30 GHz). The transistor count differs, with the PRO 5945 at 8,300 million versus 7,600 million for the 3900.

The PRO 5945 supports ECC memory, while the 3900 does not, making the PRO chip more suitable for workstation or server-adjacent tasks where data integrity is critical. The PCIe lane count differs: 24 lanes on the 3900 versus 20 on the PRO 5945. The 3900 has an unlocked multiplier, while the PRO 5945’s multiplier is locked. The 3900 was released on 2019-09-23 with a launch MSRP of $499, while the PRO 5945 was released on 2022-04-03 with no launch MSRP listed. Both are desktop parts with 12 cores and 24 threads, and both are actively in production.

FAQ

Q: Which processor has a higher boost clock?

A: The AMD Ryzen 9 PRO 5945 has a boost clock of 4.70 GHz, compared to 4.30 GHz on the AMD Ryzen 9 3900.

Q: Is the AMD Ryzen 9 3900 faster in any benchmark?

A: Yes, the 3900 wins in two head-to-head tests: data encryption (26657 versus 26313, a 1.3% lead) and random string sorting (44902 versus 43447, a 3.3% lead).

Q: Do both processors have the same amount of L3 cache?

A: Yes, both have 64 MB of L3 cache, along with identical L1 (64 KB per core) and L2 (512 KB per core) caches.

Q: Can the AMD Ryzen 9 PRO 5945 be overclocked?

A: No, the PRO 5945 has a locked multiplier. The AMD Ryzen 9 3900 has an unlocked multiplier, allowing overclocking.

Q: Which processor supports ECC memory?

A: The AMD Ryzen 9 PRO 5945 supports ECC memory, while the AMD Ryzen 9 3900 does not.

Q: What is the transistor count difference between the two?

A: The PRO 5945 has 8,300 million transistors, while the 3900 has 7,600 million, a difference of 700 million transistors.

The Verdict

The data is clear: the AMD Ryzen 9 PRO 5945 is the superior processor for virtually all workloads. Its 52.8% lead in Cinebench R15 single-core and 24.7% lead in integer math show that Zen 3 delivers a massive IPC improvement over Zen 2. The PRO 5945 wins 11 out of 13 benchmarks, and the two losses are by margins of 1.3% and 3.3%, which are unlikely to be noticeable in real-world use. The PRO 5945 also offers ECC memory support and a lower base clock with a higher boost clock, making it the more efficient and capable chip.

The AMD Ryzen 9 3900 should only be considered by users who specifically need an unlocked multiplier for overclocking or who require more PCIe lanes (24 versus 20). Its two benchmark wins are too narrow to justify choosing it over the PRO 5945 on performance grounds. For anyone building a new system or upgrading, the PRO 5945 is the obvious choice. Its single-core performance alone is worth the upgrade, and its multi-core leads ensure it will handle any task thrown at it. The 3900 remains a capable processor, but the benchmark results show that it is firmly in the previous generation, and the PRO 5945 is the clear winner in this comparison.