AMD EPYC 4585PX vs AMD Ryzen 9 PRO 9955 Comparison

The AMD Ryzen 9 PRO 9955 and the AMD EPYC 4585PX are two of the closest-matched workstation parts in the database: both sit in the 97th percentile of all recorded CPUs, both use the same 4 nm TSMC silicon on Socket AM5, and both target the server and workstation segment. The recorded data shows a clear division of labor, however. The EPYC 4585PX wins nine of eleven head-to-head benchmarks, while the Ryzen 9 PRO 9955 takes both single-threaded results. The gap between them, in short, is a story of core count, cache, and clocks.

Head-to-Head Benchmarks

The EPYC 4585PX dominates every multi-threaded test in the database. Its largest win comes in passmark physics, where it scores 6612 against 3332 for the Ryzen 9 PRO 9955, a 49.6 percent advantage that reflects how strongly the physics test scales with available threads. Integer math is nearly as lopsided: the EPYC posts 248563 versus 182312, ahead by 26.7 percent. Data encryption goes the same way, 47224 to 33754, a 28.5 percent gap.

The rest of the multi-threaded spread is consistent rather than extreme. Data compression lands at 884774 for the EPYC against 684470 for the Ryzen, a 22.6 percent lead. Floating point math favors the EPYC by 20.7 percent (153219 to 121509), extended instructions by 21 percent (69457 to 54903), and the headline passmark multithread score by 20.4 percent (68908 to 54866). Random string sorting lands 24.5 percent in the EPYC's favor at 95210 versus 71928, and even find prime numbers, a test that rewards raw clock behavior as much as parallelism, goes to the EPYC by 15.7 percent (547 to 461).

The Ryzen 9 PRO 9955 answers in exactly one place, but it is a meaningful one. It wins passmark single thread 4597 to 4538, a 1.3 percent margin. That lead is small, but it is consistent across both single-threaded entries in the database, and it comes despite the EPYC's higher boost clock. For latency-sensitive work that does not scale past a few threads, the two chips are effectively tied, with the Ryzen holding the nominal edge.

The EPYC 4585PX also carries Cinebench results the Ryzen lacks in the database: 60451 multi-core and 8534 single-core in Cinebench R23, 25389 and 3584 in R20, and 6093 and 860 in R15. The single-core scores across those three Cinebench generations sit in a tight band relative to its passmark single-thread result, reinforcing that its per-thread output is essentially on par with the Ryzen's.

Architecture Differences

On paper these are sibling designs. Both are Zen 5 parts built by TSMC on a 4 nm process, both carry the same transistor count of 16,630 million, and both use a two-die layout of 2x 70.6 mm². The Ryzen 9 PRO 9955 is codenamed Granite Ridge within the 9000 series, while the EPYC 4585PX is codenamed Grado within the EPYC 4005 series, but the shared silicon foundation is unmistakable.

The differences start with core count. The EPYC 4585PX has 16 cores and 32 threads against 12 cores and 24 threads for the Ryzen 9 PRO 9955, a 33 percent advantage in hardware threads that explains nearly every multi-threaded result above. Cache is the second divider: the EPYC carries 128 MB of L3 versus 64 MB on the Ryzen, twice the shared last-level cache. Both parts keep identical per-core L1 of 80 KB and per-core L2 of 1 MB.

Clocks also differ. The Ryzen 9 PRO 9955 runs a base clock of 3.40 GHz with a 5.40 GHz boost, while the EPYC 4585PX runs a substantially higher 4.30 GHz base and boosts to 5.70 GHz. That higher base, layered on top of the extra cores, is why the EPYC wins even lightly threaded compute tests like prime number search. The trade-off is power: the EPYC is rated at 170 W TDP versus 120 W for the Ryzen.

Everything else lines up. Both support DDR5 on a dual-channel bus with 89.6 GB/s of bandwidth, both offer ECC memory, both expose 24 lanes of PCIe Gen 5 from the CPU, and both include Radeon integrated graphics. Both are locked, with no unlocked multiplier on either part. Both are active production parts, with the EPYC 4585PX carrying a launch MSRP of $699 and having entered the database earlier, with the Ryzen 9 PRO 9955 recorded later.

FAQ

Q: Which CPU is faster overall?

A: The EPYC 4585PX. It wins nine of eleven head-to-head benchmarks, including the passmark multithread score at 68908 versus 54866, a 20.4 percent lead driven by its 16 cores and 32 threads.

Q: Which one is faster in single-threaded work?

A: The Ryzen 9 PRO 9955, by a hair. It scores 4597 in passmark single thread against 4538 for the EPYC 4585PX, a 1.3 percent margin that is within noise for most real workloads.

Q: Do they use the same socket and platform?

A: Yes. Both are Socket AM5 parts with dual-channel DDR5, 24 PCIe Gen 5 CPU lanes, ECC support, and identical 89.6 GB/s memory bandwidth, so platform capability is not a differentiator here.

Q: How do they compare against rival CPUs in the database?

A: Both sit in the 97th percentile. The Ryzen 9 PRO 9955's average benchmark score of 110612 places it 1.8 percent ahead of the Intel Xeon w7-2595X, 3.9 percent ahead of the Ryzen 9 9850HX, 4.2 percent ahead of the Xeon w7-3555, and 4 percent behind the Xeon 6527P. The EPYC 4585PX averages 99324, landing 0.8 percent ahead of the Threadripper PRO 5965WX, 1.9 percent ahead of the Ryzen 9 9955HX3D, and 1.7 and 2.9 percent behind the Threadripper PRO 9955WX and EPYC 7513 respectively.

Q: What is the difference in cache?

A: The EPYC 4585PX has 128 MB of L3 cache, double the 64 MB on the Ryzen 9 PRO 9955. Per-core L1 and L2 are identical at 80 KB and 1 MB respectively.

Q: Which chip runs cooler by design?

A: The Ryzen 9 PRO 9955 is rated at 120 W TDP versus 170 W for the EPYC 4585PX, so it demands less cooling headroom in the recorded specifications.

Specification Differences

The two parts differ in only a handful of fields. The Ryzen 9 PRO 9955 has 12 cores and 24 threads; the EPYC 4585PX has 16 cores and 32 threads. Base and boost clocks are 3.40 and 5.40 GHz on the Ryzen against 4.30 and 5.70 GHz on the EPYC. L3 cache is 64 MB versus 128 MB. TDP is 120 W versus 170 W. Codenames and series differ, Granite Ridge in the 9000 series versus Grado in the EPYC 4005 series, and part numbers are 100-000001971 versus 100-000001561. The EPYC 4585PX carries a launch MSRP of $699 and an earlier release date in the database.

Every other specification is shared: 4 nm TSMC process, 16,630 million transistors, 2x 70.6 mm² die size, 80 KB L1 and 1 MB L2 per core, DDR5 support on a dual-channel bus with 89.6 GB/s bandwidth, ECC, 24 PCIe Gen 5 CPU lanes, Radeon integrated graphics, Socket AM5, a locked multiplier, server/workstation segmentation, and active production status.

Where Each One Wins

The EPYC 4585PX is the pick wherever throughput is the metric. Its wins span the entire multi-threaded suite: a 49.6 percent advantage in physics, 28.5 percent in encryption, 26.7 percent in integer math, 24.5 percent in string sorting, 22.6 percent in compression, 21 percent in extended instructions, 20.7 percent in floating point, and 20.4 percent in the overall multithread score. Render farms, compile servers, batch media encoding, simulation, and virtualization workloads all map directly onto that profile, and its doubled L3 cache further helps data-heavy server duty. Its Cinebench R23 multi-core score of 60451 underscores the rendering pedigree.

The Ryzen 9 PRO 9955 is the pick where per-thread responsiveness matters more than aggregate throughput, and where efficiency counts. Its 1.3 percent single-thread win at 4597 means latency-bound applications, interactive tooling, and lightly threaded legacy software give up nothing to the EPYC, and its lower 120 W TDP rating makes it the less demanding part to cool and integrate. It also holds the higher average benchmark score in the database at 110612 versus 99324, and stacks up well against its nearest rivals, trading blows with the Intel Xeon w7-2595X, w7-3555, and 6527P within a four percent band.

The verdict from the data is straightforward. Need cores and cache: the EPYC 4585PX wins, and wins big. Need single-thread parity with a leaner power envelope on the same AM5 platform: the Ryzen 9 PRO 9955 delivers it.