AMD Ryzen Embedded 8645HS vs AMD Ryzen Embedded 9900X Comparison

The Verdict

The recorded data presents two fundamentally different Ryzen Embedded processors. The AMD Ryzen Embedded 8645HS is a 6-core, 12-thread mobile part built on Zen 4 with a 45 W TDP, while the AMD Ryzen Embedded 9900X is a 12-core, 24-thread desktop part built on Zen 5 with a 120 W TDP. The benchmark results are empty, and the win counts for each processor are zero, meaning the database contains no head-to-head performance measurements to separate them by speed. The percentile ranking for both is identical at 50, indicating they sit at the median of all CPUs tracked, though this is based on an average benchmark score of zero for each, so the percentile likely reflects the absence of recorded scores rather than actual parity.

Given the data, the choice hinges entirely on the structural differences. The 8645HS targets mobile and embedded low-power applications, with a lower TDP, an AMD Socket FP8, and a Radeon 760M integrated GPU. The 9900X targets desktop and high-throughput embedded roles, with double the cores, a higher boost clock, a larger L3 cache, and PCIe Gen 5 support. Neither processor shows a benchmark victory in the database, so the verdict is dictated by platform requirements: the 8645HS for power-sensitive, compact deployments, and the 9900X for multi-threaded workloads where the 120 W TDP and 24 threads are acceptable.

Architecture Differences

The two processors belong to different generations and microarchitectures. The 8645HS is listed under the 8000 series, using Zen 4 with the codename Hawk Point, released on April 1, 2024. The 9900X is from the 9000 series, using Zen 5 with the codename Granite Ridge, released on October 6, 2025. This generational gap means the 9900X benefits from the newer Zen 5 core design, which typically improves instructions per clock, though specific IPC numbers are not present in the database.

The process node is identical for both: 4 nm, fabricated by TSMC. However, the transistor counts and die sizes differ significantly. The 8645HS has 25,000 million transistors on a single 178 mm² die. The 9900X has 16,630 million transistors spread across two 70.6 mm² dies, for a combined die area of approximately 141.2 mm². The 9900X uses a chiplet design with two CCDs, while the 8645HS is a monolithic die, a structural difference that affects manufacturing yields and thermal density.

Cache hierarchies diverge markedly. The 8645HS has 64 KB of L1 per core, 1 MB of L2 per core, and 16 MB of shared L3. The 9900X has 80 KB of L1 per core, 1 MB of L2 per core, and 64 MB of L3. The 9900X provides four times the L3 capacity, which is critical for workloads with large working sets or heavy inter-core communication. Neither processor supports 3D V-Cache.

Memory support is the same in type and bandwidth: both use DDR5 with dual-channel memory and a bandwidth of 89.6 GB/s. Both support ECC memory, which is a requirement for embedded reliability. PCIe capabilities differ: the 8645HS uses Gen 4 with 20 lanes (CPU only), while the 9900X uses Gen 5 with 24 lanes (CPU only). This gives the 9900X both more lanes and a faster generation for expansion.

The integrated graphics differ as well. The 8645HS includes a Radeon 760M, a specific GPU model, while the 9900X has a generic Radeon Graphics solution. The 760M is a named part, suggesting a more capable iGPU for the mobile chip, though no benchmark scores exist to quantify the difference.

Head-to-Head Benchmarks

The database records no head-to-head benchmark results for these two processors. The `headToHeadBenchmarks` array is empty, and both `winsA` and `winsB` are zero. Consequently, there are no exact scores, percentages, or deltas to report for multi-core, single-core, gaming, or productivity tests.

In the absence of measured data, the only quantitative comparisons come from the specification fields. The 9900X has a base clock of 4.40 GHz versus 4.30 GHz for the 8645HS, a 0.10 GHz advantage. The boost clock is more decisive: the 9900X reaches 5.60 GHz, while the 8645HS tops out at 5.00 GHz, a 0.60 GHz gap. The core count difference is the largest structural gap: the 9900X has 12 cores and 24 threads, exactly double the 6 cores and 12 threads of the 8645HS. For any parallel workload that scales with cores, the 9900X should theoretically process roughly twice the work per clock cycle, assuming equal IPC per core, though Zen 5 may improve upon Zen 4 in that regard.

The L3 cache difference is also notable: 64 MB versus 16 MB, a 4x multiplier. The 9900X also offers PCIe Gen 5 versus Gen 4, which doubles the available bandwidth per lane for compatible devices. The TDP difference is 120 W versus 45 W, meaning the 9900X consumes 2.67x the power budget of the 8645HS.

Because the benchmark arrays are empty, the analysis cannot state which processor wins in any specific test. The data implies that the 9900X is positioned as the higher-performance part based on cores, clocks, cache, and PCIe generation, but the absence of recorded measurements prevents a definitive performance verdict.

FAQ

Q: Which processor has more cores?

A: The AMD Ryzen Embedded 9900X has 12 cores and 24 threads, while the AMD Ryzen Embedded 8645HS has 6 cores and 12 threads.

Q: Do both processors support ECC memory?

A: Yes, both the 8645HS and the 9900X have ECC memory support set to true in the database, and both use DDR5 memory.

Q: What is the difference in L3 cache capacity?

A: The 9900X has 64 MB of shared L3 cache, while the 8645HS has 16 MB of shared L3 cache, a 4x difference.

Q: Which processor has a higher boost clock?

A: The 9900X has a boost clock of 5.60 GHz, compared to 5.00 GHz for the 8645HS.

Q: What PCIe generation does each processor support?

A: The 8645HS supports PCIe Gen 4 with 20 lanes (CPU only), while the 9900X supports PCIe Gen 5 with 24 lanes (CPU only).

Q: Are there any recorded benchmark scores for either processor?

A: No, the database shows an average benchmark score of zero for both processors, and the head-to-head benchmark array is empty.

Where Each One Wins

Without benchmark results, the win analysis must rely on architectural and specification advantages. The 8645HS wins in power efficiency: its 45 W TDP is 75 W lower than the 9900X's 120 W TDP, making it suitable for thermally constrained embedded environments or fanless designs where the 9900X would require substantial cooling. The 8645HS also uses the AMD Socket FP8, which is a mobile socket, and its monolithic 178 mm² die simplifies heat distribution across a single die. The Radeon 760M integrated GPU is a named, specific model, whereas the 9900X's Radeon Graphics is generic, suggesting the 8645HS may have a more defined graphics capability for display output or light GPU compute, though no benchmarks confirm this.

The 9900X wins in raw compute potential. It has double the cores and threads, a 0.60 GHz higher boost clock, and a 64 MB L3 cache compared to 16 MB. For multi-threaded server workloads, database processing, or compilation tasks that scale across 24 threads, the 9900X is the clear choice. Its PCIe Gen 5 support with 24 lanes enables faster NVMe storage and high-bandwidth accelerators, whereas the 8645HS is limited to PCIe Gen 4 with 20 lanes. The 9900X also benefits from the newer Zen 5 architecture (Granite Ridge) versus Zen 4 (Hawk Point), which may deliver better instructions per clock, though no IPC data is recorded.

The 9900X has an unlocked multiplier, while the 8645HS does not. This allows the 9900X to be overclocked, provided the platform supports it, which is a flexibility win for desktop or embedded users who can manage the extra power draw. The 8645HS is locked, limiting performance tuning to fixed settings.

For memory bandwidth, both processors are equal at 89.6 GB/s, so neither wins on that front. For socket compatibility, the 9900X uses AMD Socket AM5, a desktop standard, while the 8645HS uses AMD Socket FP8, a mobile standard, so the platform choice will dictate which is viable.

Specification Differences

The two processors differ in nearly every major specification field. The 8645HS is from the 8000 series, while the 9900X is from the 9000 series. The 8645HS uses Zen 4 (Hawk Point), and the 9900X uses Zen 5 (Granite Ridge). Cores differ: 6 versus 12. Threads differ: 12 versus 24. Base clocks are 4.30 GHz versus 4.40 GHz, and boost clocks are 5.00 GHz versus 5.60 GHz. TDP is 45 W versus 120 W. Sockets are AMD Socket FP8 versus AMD Socket AM5. Transistor counts are 25,000 million versus 16,630 million. Die sizes are 178 mm² versus 2x 70.6 mm². L1 cache is 64 KB per core versus 80 KB per core. L2 cache is 1 MB per core for both, so that field matches. L3 cache is 16 MB shared versus 64 MB. PCIe is Gen 4 with 20 lanes versus Gen 5 with 24 lanes. Integrated graphics are Radeon 760M versus Radeon Graphics. Release dates are April 1, 2024 versus October 6, 2025. The multiplier is locked on the 8645HS and unlocked on the 9900X. The part number for the 9900X is 100-000000662E, while the 8645HS has an unknown part number. Market segments are Mobile versus Desktop. Both share the same process node (4 nm), foundry (TSMC), memory support (DDR5), memory bus (dual-channel), memory bandwidth (89.6 GB/s), and ECC support (true). Neither has a launch MSRP recorded in the database, and both are marked as Active in production status.