AMD Instinct MI300 vs AMD Instinct MI455X Comparison

Head-to-Head Benchmarks

The recorded database contains no direct head-to-head benchmark results for the AMD Instinct MI300 and AMD Instinct MI455X. Both accelerators hold a 50th percentile position in the overall GPU distribution, and neither has an average benchmark score recorded. The absence of measured performance data means the comparison must rely entirely on architectural specifications and theoretical throughput figures derived from the factory specifications.

The most decisive gap appears in raw compute throughput. The MI455X delivers 157.3 TFLOPS for both FP32 and FP16 operations, while the MI300 reaches 47.87 TFLOPS in both precisions. That places the MI455X at roughly 3.3 times the FP32 throughput of the MI300, a substantial generational leap. Texture rate follows a similar pattern: the MI455X achieves 2,457.6 GTexel/s versus 1,496.0 GTexel/s for the MI300, a 64 percent advantage. Both parts report 0 MPixel/s pixel rates, as neither has ROPs enabled, so rasterization throughput is effectively nonexistent for both.

Memory bandwidth is another area where the MI455X dominates. The newer accelerator pairs 432 GB of HBM4 memory across a 24,576-bit bus to reach 23.3 TB/s. The MI300 uses 128 GB of HBM3 on an 8,192-bit bus for 5.32 TB/s. The MI455X therefore carries 3.4 times the memory capacity and 4.4 times the bandwidth. Effective memory clock also rises from 5.2 Gbps to 7.6 Gbps, while the memory base clock moves from 1,300 MHz to 1,900 MHz.

Boost clocks show a narrower gap. The MI300 boosts to 1,700 MHz, while the MI455X reaches 2,400 MHz, a 41 percent increase. Both share a 1,000 MHz base clock. The MI455X also expands shading units from 14,080 to 32,768, more than doubling the compute core count, and increases texture mapping units from 880 to 1,024, a 16 percent rise.

Transistor counts reflect the manufacturing leap. The MI455X packs 320,000 million transistors on a 2,990 mm² die using a 2 nm TSMC process. The MI300 contains 153,000 million transistors on a 1,017 mm² die fabricated on 5 nm TSMC. Interestingly, the MI300 has a higher transistor density at 150.4M per mm², compared to 107.0M per mm² for the MI455X, which suggests the newer part uses a more spacious layout or incorporates different structural elements.

Power requirements scale dramatically with the performance increase. The MI455X carries a 2,300 W TDP and a suggested 2,700 W power supply, whereas the MI300 draws 600 W with a 1,000 W suggested PSU. The MI455X uses no power connectors and ships as an EAM Module, while the MI300 relies on 2x 8-pin connectors. Both use PCIe interfaces, with the MI300 on PCIe 5.0 x16 and the MI455X on PCIe 6.0 x16.

Where Each One Wins

The MI300 wins in operational accessibility. Its 600 W TDP fits within conventional server power envelopes, and its 2x 8-pin connectors match standard power delivery infrastructure. Physical dimensions are recorded at 267 mm length and 111 mm height, allowing installation in typical accelerator slots. The MI455X, by contrast, requires a 2,300 W power budget and a 2,700 W suggested PSU, which restricts deployment to specialized high-density systems. The EAM Module form factor with no power connectors indicates a proprietary installation approach.

The MI300 also wins on transistor density. At 150.4M transistors per mm², it exceeds the MI455X density of 107.0M per mm², meaning the older part packs its resources more tightly. This could translate to better thermal concentration management or simpler manufacturing yields, though the database does not provide yield data.

The MI455X wins everywhere raw capability matters. Its FP32 throughput of 157.3 TFLOPS versus 47.87 TFLOPS gives it a 3.3x edge in general compute workloads. The FP16 ratio matches at 3.3x, so mixed-precision training and inference tasks see the same scaling. Memory capacity of 432 GB versus 128 GB provides 3.4x more working set headroom for large model parameters or massive datasets. Bandwidth of 23.3 TB/s versus 5.32 TB/s means the MI455X can feed its compute units far more effectively, reducing stalls in memory-bound kernels.

Texture rate favors the MI455X at 2,457.6 GTexel/s versus 1,496.0 GTexel/s, a 64 percent advantage. While neither part targets traditional graphics workloads, texture sampling throughput can matter in certain scientific visualization or signal processing pipelines. The MI455X also doubles the shading units, which directly scales wavefront execution capacity.

The MI455X wins on clock headroom. Its 2,400 MHz boost clock versus 1,700 MHz for the MI300 represents a 41 percent frequency advantage, which compounds with the wider execution resources. The memory subsystem also favors the newer part with 7.6 Gbps effective speed versus 5.2 Gbps.

The MI300 wins on release timing. Its 2023 launch date (2023-01-03) means the part has been available for longer, and its predecessor lineage from Radeon Instinct suggests established software stacks. The MI455X arrives later with a 2026-07-22 release date, so ecosystem maturity may still be developing.

Architecture Differences

The MI300 uses CDNA 3.0 architecture on a 5 nm TSMC process, while the MI455X uses CDNA 5.0 architecture on 2 nm TSMC. The chip designations differ as well: the MI300 carries the Aqua Vanjaram chip, while the MI455X uses the MI450 256CU die. Both belong to the Instinct (MIx) generation and share the Radeon Instinct predecessor label, but the architectural generation gap spans two full revisions.

Transistor integration scales from 153,000 million on the MI300 to 320,000 million on the MI455X, more than doubling the total transistor budget. Die size grows from 1,017 mm² to 2,990 mm², nearly tripling the physical area. The transistor density decrease from 150.4M per mm² to 107.0M per mm² indicates the newer process node allows larger structures or additional interconnect layers, even though the per-area count drops.

Memory architecture differs fundamentally. The MI300 uses HBM3 with 128 GB capacity, an 8,192-bit bus, and 5.32 TB/s bandwidth. The MI455X moves to HBM4 with 432 GB capacity, a 24,576-bit bus, and 23.3 TB/s bandwidth. The bus width triples, and the bandwidth more than quadruples. Effective memory speed increases from 5.2 Gbps to 7.6 Gbps.

Compute resources scale significantly. Shading units increase from 14,080 to 32,768, a 2.33x expansion. Texture mapping units grow from 880 to 1,024, a more modest 1.16x increase. Neither part includes ray tracing cores or tensor cores in the recorded data, and both report N/A for DirectX, OpenGL, and Vulkan APIs, confirming their compute-only positioning. Both have zero ROPs and zero pixel rate, so display output is absent on both.

The MI455X introduces PCIe 6.0 x16 connectivity, while the MI300 uses PCIe 5.0 x16. This doubles the potential host interface bandwidth for data transfer, though the database does not record specific transfer rates. The MI455X also changes the physical form factor to an EAM Module with no power connectors, whereas the MI300 uses a standard slot with 2x 8-pin power. The MI455X has no recorded dimensions, while the MI300 measures 267 mm by 111 mm.

Power delivery differs substantially. The MI300's 600 W TDP pairs with a 1,000 W suggested PSU. The MI455X's 2,300 W TDP requires a 2,700 W suggested PSU, a 3.8x increase in power draw and a 2.7x increase in PSU recommendation. Clock behavior also diverges: base clocks match at 1,000 MHz, but boost clocks separate to 1,700 MHz versus 2,400 MHz.

FAQ

Q: How much faster is the MI455X in FP32 compute than the MI300?

A: The MI455X delivers 157.3 TFLOPS FP32, while the MI300 delivers 47.87 TFLOPS. The MI455X is approximately 3.3 times faster in FP32 throughput.

Q: What memory configuration differences exist between the two accelerators?

A: The MI300 uses 128 GB of HBM3 with an 8,192-bit bus and 5.32 TB/s bandwidth. The MI455X uses 432 GB of HBM4 with a 24,576-bit bus and 23.3 TB/s bandwidth, providing 3.4x more capacity and 4.4x more bandwidth.

Q: Which process nodes do the two chips use?

A: The MI300 is fabricated on a 5 nm TSMC process, while the MI455X uses a 2 nm TSMC process. Both are manufactured by TSMC.

Q: What are the power requirements for each accelerator?

A: The MI300 has a 600 W TDP with a suggested 1,000 W power supply and uses 2x 8-pin connectors. The MI455X has a 2,300 W TDP with a suggested 2,700 W power supply and uses no power connectors, shipping as an EAM Module.

Q: Do either of these accelerators support graphics APIs?

A: No. Both report N/A for DirectX, OpenGL, and Vulkan, and both have zero pixel rate with no display outputs. They are compute-only accelerators.

Q: What is the release date difference between the two parts?

A: The MI300 was released on 2023-01-03, while the MI455X is dated 2026-07-22. The MI455X launches roughly three and a half years later.

The Verdict

The data indicates a clear generational split. The MI455X offers dramatically higher compute throughput, memory capacity, and bandwidth, making it the superior choice for workloads that can utilize its scale. Its 157.3 TFLOPS FP32 performance and 23.3 TB/s bandwidth position it for large-scale AI training, scientific simulation, and data-intensive inference tasks. The 432 GB memory capacity accommodates models that would not fit within 128 GB.

However, the MI455X demands infrastructure that many deployments cannot provide. Its 2,300 W TDP and 2,700 W suggested PSU require specialized power delivery and cooling systems. The EAM Module form factor with no power connectors suggests proprietary integration, which may limit compatibility with standard server chassis. The lack of recorded dimensions also complicates physical planning.

The MI300 remains viable for environments with conventional power budgets. Its 600 W TDP and standard 2x 8-pin connectors allow integration into existing server infrastructure. The 5 nm process with 150.4M transistors per mm² density indicates efficient manufacturing, and the 2023 release date means the software ecosystem has had time to mature.

For organizations with power and cooling headroom, the MI455X delivers 3.3x the FP32 throughput and 4.4x the memory bandwidth, which can translate to proportionally shorter job completion times. For those constrained to standard power envelopes, the MI300 provides a functional path with 47.87 TFLOPS and 5.32 TB/s, sufficient for many mid-range workloads. The choice comes down to whether the infrastructure can support the MI455X's 2,300 W draw and whether the workload requires more than 128 GB of memory or more than 5.32 TB/s of bandwidth. If neither constraint applies, the MI300 may be the practical option. If both apply, the MI455X is the only part in this comparison that meets the requirement.