AMD Instinct MI455X vs AMD Radeon Instinct MI300A Comparison

Head-to-Head Benchmarks

The recorded database contains no measured benchmark scores for either the AMD Instinct MI455X or the AMD Radeon Instinct MI300A. Both entries show an average benchmark score of 0 and no wins in head-to-head testing. The percentile ranking against all GPUs is identical at 50 for both accelerators, placing them at the median of the database distribution despite the absence of empirical test data.

Without recorded frame rates, compute throughput measurements, or latency figures, a direct numerical comparison of real-world performance cannot be established from the available facts. The FP32 and FP16 specifications offer the only quantitative performance indicators, and these represent theoretical peak rates rather than observed benchmark outcomes. The MI455X lists 157.3 TFLOPS for both FP32 and FP16 at a 1:1 ratio, while the MI300A shows 81.72 TFLOPS FP32 and 653.7 TFLOPS FP16 at an 8:1 ratio. These figures indicate the MI455X holds a 92.5% advantage in single-precision floating-point throughput, while the MI300A leads in half-precision throughput by a factor of roughly 4.16x based on the listed peak rates.

The texture rate comparison favors the MI300A slightly, with 2,553.6 GTexel/s versus 2,457.6 GTexel/s for the MI455X, a difference of approximately 3.9%. Both parts show 0 MPixel/s pixel rates and 0 ROPs, confirming neither accelerator is designed for rasterized graphics output.

Where Each One Wins

The MI455X establishes its advantage in raw FP32 compute density. Its 157.3 TFLOPS single-precision rating doubles the MI300A's 81.72 TFLOPS, making it the stronger candidate for workloads that rely on traditional floating-point math without mixed-precision acceleration. The newer CDNA 5.0 architecture, fabricated on a 2 nm process at TSMC, supports this higher throughput per clock despite the lower 2400 MHz boost versus 2100 MHz on the MI300A. The MI455X also delivers substantially more memory capacity at 432 GB of HBM4 compared to the MI300A's 192 GB of HBM3. Memory bandwidth follows the same pattern: 23.3 TB/s for the MI455X versus 10.3 TB/s for the MI300A, a 126% bandwidth advantage that benefits large model training and inference workloads where data movement dominates execution time.

The MI300A wins in half-precision compute. Its 653.7 TFLOPS FP16 rating at an 8:1 ratio exceeds the MI455X's 157.3 TFLOPS at a 1:1 ratio by a wide margin. This makes the MI300A the more appropriate choice for AI training and inference pipelines that operate natively in FP16 or mixed-precision formats. The MI300A also holds advantages in transistor density, with 150.4 million transistors per square millimeter versus 107.0 million for the MI455X, and in texture filtering throughput at 2,553.6 GTexel/s. Its 750 W TDP and 1150 W suggested PSU represent a much lower power envelope than the MI455X's 2300 W TDP and 2700 W suggested PSU, which matters for dense server deployments with cooling constraints.

Architecture Differences

The two accelerators belong to different CDNA generations and process nodes. The MI455X uses CDNA 5.0 on a 2 nm TSMC process, while the MI300A uses CDNA 3.0 on a 5 nm TSMC process. The MI455X integrates 320,000 million transistors across a 2990 mm² die, whereas the MI300A packs 153,000 million transistors into a 1017 mm² die. The transistor density figures reflect the process gap: 107.0M transistors per mm² for the older design node in the MI455X versus 150.4M per mm² for the MI300A, an inversion that suggests the MI455X's larger die and newer node permit a different balance of compute units and memory logic.

Compute unit configurations diverge significantly. The MI455X contains 32,768 shading units and 1,024 TMUs, while the MI300A contains 19,456 shading units and 1,216 TMUs. The MI455X carries more than twice the shader count but fewer texture units, and its chip identifier is listed as MI450 256CU. The MI300A uses the Aqua Vanjaram chip. Neither accelerator includes RT cores or tensor cores as separate hardware blocks, and both have zero ROPs, confirming their exclusive data-center orientation.

Memory subsystems differ by generation and scale. The MI455X uses HBM4 with a 24,576-bit bus width and 432 GB capacity, running at 1900 MHz with 7.6 Gbps effective data rate. The MI300A uses HBM3 with an 8,192-bit bus and 192 GB capacity, running at 2525 MHz with 10.1 Gbps effective. The MI455X's threefold bus width advantage drives its 23.3 TB/s bandwidth despite the lower memory clock, while the MI300A's narrower bus limits it to 10.3 TB/s. The MI455X also adopts PCIe 6.0 x16 for host connectivity, one generation ahead of the MI300A's PCIe 5.0 x16.

Power delivery differs in scale. The MI455X draws 2300 W TDP with a suggested PSU of 2700 W, while the MI300A draws 750 W TDP with a suggested PSU of 1150 W. Both use module form factors, EAM for the MI455X and OAM for the MI300A, with no power connectors because power is delivered through the module socket. Neither unit provides display outputs, and the MI455X lists no supported graphics APIs (DirectX, OpenGL, Vulkan all marked N/A), while the MI300A's API support fields are empty in the database.

Release timing shows a generational gap of roughly two and a half years. The MI300A entered the database with a release date of December 2023, while the MI455X followed in July 2026. The MI300A's predecessor is listed as FirePro Data Center, and the MI455X's predecessor is Radeon Instinct, indicating the product lineage shift within AMD's accelerator lineup.

FAQ

Q: Which accelerator has higher FP32 compute throughput?

A: The AMD Instinct MI455X lists 157.3 TFLOPS FP32, which is 92.5% higher than the MI300A's 81.72 TFLOPS. The MI455X's boost clock of 2400 MHz and 32,768 shading units contribute to this lead.

Q: How do the memory capacities compare?

A: The MI455X provides 432 GB of HBM4 across a 24,576-bit bus, while the MI300A provides 192 GB of HBM3 across an 8,192-bit bus. The MI455X also leads in bandwidth: 23.3 TB/s versus 10.3 TB/s.

Q: Which part is better for FP16 workloads?

A: The MI300A lists 653.7 TFLOPS FP16 at an 8:1 ratio, which is approximately 4.16x higher than the MI455X's 157.3 TFLOPS FP16 at a 1:1 ratio. The MI300A's FP16 capability makes it the stronger choice for mixed-precision AI workloads based on the recorded specs.

Q: What is the power requirement difference?

A: The MI455X has a 2300 W TDP and a suggested PSU of 2700 W. The MI300A has a 750 W TDP and a suggested PSU of 1150 W. The MI300A requires roughly one-third the power of the MI455X according to these figures.

Q: Do these accelerators support graphics output?

A: No. Both list no display outputs, 0 MPixel/s pixel rates, and 0 ROPs. The MI455X explicitly lists DirectX, OpenGL, and Vulkan as N/A.

Q: What process nodes do these chips use?

A: The MI455X uses a 2 nm TSMC process, while the MI300A uses a 5 nm TSMC process. The MI455X integrates 320,000 million transistors on a 2990 mm² die, while the MI300A integrates 153,000 million transistors on a 1017 mm² die.

The Verdict

The data supports a clear division of roles. For single-precision compute tasks, large memory footprints, and high-bandwidth data movement, the MI455X dominates on every recorded metric: 157.3 TFLOPS FP32, 432 GB memory, 23.3 TB/s bandwidth, and 2,457.6 GTexel/s texture rate. Its 2400 MHz boost clock and 32,768 shading units provide the raw throughput for FP32-heavy scientific simulation, data processing, and traditional HPC workloads that do not convert to reduced precision.

For half-precision AI workloads, the MI300A holds a decisive lead with 653.7 TFLOPS FP16, which is more than four times the MI455X's FP16 rating. Its lower 750 W TDP and 1150 W suggested PSU also make it substantially easier to deploy in power-constrained environments. The MI300A's 10.3 TB/s bandwidth and 192 GB HBM3 capacity remain substantial, even if smaller than the MI455X's memory subsystem.

Neither accelerator shows any graphics capability, and both sit at the 50th percentile in the database's all-GPU ranking, though this reflects the absence of benchmark scores rather than measured performance parity. The MI455X represents a generational step forward in process technology, memory technology, and host interface, with CDNA 5.0, HBM4, and PCIe 6.0. The MI300A leverages its older CDNA 3.0 design to deliver exceptional FP16 throughput and a much lower power envelope within the same module-based form factor.

The choice between these two parts depends on workload precision requirements and power budgets. The MI455X is the higher-throughput FP32 device with the larger memory pool, suitable for workloads that need maximum single-precision compute and massive model residency. The MI300A is the higher-throughput FP16 device with a fraction of the power draw, suitable for AI training and inference at reduced precision where its 8:1 FP16 ratio provides a substantial throughput advantage. The recorded specifications offer no basis for declaring an overall winner, only a confirmation that each accelerator targets a different segment of the data-center compute market.