AMD Instinct MI300A vs AMD Instinct MI455X Comparison

Head-to-Head Benchmarks

The database contains no head-to-head benchmark entries for the AMD Instinct MI300A versus the AMD Instinct MI455X. With zero recorded wins for either accelerator and an empty head-to-head benchmark array, direct performance comparisons cannot be established from measured data. Both parts sit at the 50th percentile against all GPUs in the database, and both carry an average benchmark score of 0, indicating that no standardized workload results have been logged for either device.

The absence of benchmark data is itself informative. The MI300A, released in December 2023, belongs to the CDNA 3.0 generation and has had time to accumulate test results, yet none appear in the database. The MI455X, with a release date in July 2026, is a newer design under the CDNA 5.0 architecture, and its lack of recorded benchmarks is consistent with a product that may still be in early qualification or pre-production validation.

What the data does allow is a specification-level projection. The MI455X lists 157.3 TFLOPS of FP32 compute, which is 2.57 times the MI300A's 61.29 TFLOPS. The texture rate difference is narrower: the MI455X delivers 2,457.6 GTexel/s against 1,915.2 GTexel/s, a 28.3% advantage. Memory bandwidth shows a more dramatic separation, with the MI455X at 23.3 TB/s versus 5.32 TB/s for the MI300A, a 4.38x gap.

Neither part has pixel rate capability; both are recorded at 0 MPixel/s, and both have no display outputs. The APIs for DirectX, OpenGL, and Vulkan are all listed as N/A for both accelerators, confirming their purpose as compute-only devices rather than graphics cards.

FAQ

Q: Which accelerator has the higher FP32 compute throughput?

A: The AMD Instinct MI455X lists 157.3 TFLOPS of FP32 compute, compared to 61.29 TFLOPS for the AMD Instinct MI300A. The MI455X also lists FP16 at 157.3 TFLOPS with a 1:1 ratio, while the MI300A has no recorded FP16 figure.

Q: How do the memory subsystems differ?

A: The MI300A uses 128 GB of HBM3 memory on an 8192-bit bus with 5.32 TB/s bandwidth and 1300 MHz memory clock (5.2 Gbps effective). The MI455X uses 432 GB of HBM4 on a 24576-bit bus with 23.3 TB/s bandwidth and 1900 MHz memory clock (7.6 Gbps effective). The MI455X has 3.375x the capacity and 4.38x the bandwidth.

Q: What are the thermal design power ratings?

A: The MI300A is rated at 750 W with a suggested power supply of 1150 W. The MI455X is rated at 2300 W with a suggested power supply of 2700 W. The MI455X consumes 3.07x the power of the MI300A.

Q: What process nodes and foundries are used?

A: Both use TSMC as the foundry. The MI300A is built on a 5 nm process with 153,000 million transistors on a 1017 mm² die. The MI455X uses a 2 nm process with 320,000 million transistors on a 2990 mm² die.

Q: What are the shading unit and texture unit counts?

A: The MI300A has 14,592 shading units and 912 TMUs. The MI455X has 32,768 shading units and 1024 TMUs. The MI455X has 2.25x the shading units and 1.12x the texture units.

Q: What interface and form factor does each use?

A: The MI300A uses a PCIe 5.0 x16 bus interface and comes as an OAM Module. The MI455X uses a PCIe 6.0 x16 bus interface and comes as an EAM Module. Neither has power connectors or display outputs.

The Verdict

The recorded data supports distinct roles for these two accelerators. The AMD Instinct MI300A, released in December 2023, is the lower-power option at 750 W with a suggested power supply of 1150 W. Its 128 GB of HBM3 memory and 5.32 TB/s bandwidth suit workloads that do not require the extreme memory footprint of the newer part. The 5 nm process with 153,000 million transistors on a 1017 mm² die places it in a more conventional power envelope for data center deployment.

The AMD Instinct MI455X, releasing in July 2026, is positioned as a high-capacity, high-throughput compute accelerator. Its 432 GB of HBM4 memory on a 24576-bit bus delivers 23.3 TB/s, which is 4.38x the MI300A's bandwidth. The 2 nm process packs 320,000 million transistors onto a 2990 mm² die, and the 2300 W TDP with 2700 W suggested power supply indicates a system designed around maximum compute density rather than power efficiency.

For FP32-heavy workloads, the MI455X's 157.3 TFLOPS is 2.57x the MI300A's 61.29 TFLOPS. The FP16 capability at 157.3 TFLOPS with a 1:1 ratio adds flexibility for mixed-precision training and inference. The MI300A has no recorded FP16 figure, leaving its half-precision performance unspecified in the database.

The choice between these parts depends on whether the workload requires the MI455X's massive memory bandwidth and compute throughput, or whether the MI300A's lower power draw and established CDNA 3.0 platform suffice. The 28.3% texture rate advantage of the MI455X is modest compared to its memory and compute advantages, suggesting that memory-bound and compute-bound workloads will see the largest gains from the newer accelerator. Neither part supports graphics APIs or display output, so both are strictly for compute workloads.

Specification Differences

The two accelerators differ across nearly every measured specification. The MI300A uses the Aqua Vanjaram chip with CDNA 3.0 architecture, while the MI455X uses the MI450 256CU chip with CDNA 5.0 architecture. The process node moves from 5 nm to 2 nm, and transistor count rises from 153,000 million to 320,000 million. Die size increases from 1017 mm² to 2990 mm², while transistor density actually decreases from 150.4M per mm² to 107.0M per mm².

Boost clocks differ: the MI300A boosts to 2100 MHz, the MI455X to 2400 MHz. Both share a 1000 MHz base clock. Memory clocks also differ, with the MI300A at 1300 MHz (5.2 Gbps effective) and the MI455X at 1900 MHz (7.6 Gbps effective).

Memory capacity, type, bus width, and bandwidth all differ. The MI300A has 128 GB HBM3 on 8192 bit with 5.32 TB/s. The MI455X has 432 GB HBM4 on 24576 bit with 23.3 TB/s. Shading units increase from 14,592 to 32,768, TMUs from 912 to 1024, and both have 0 ROPs.

FP32 compute rises from 61.29 TFLOPS to 157.3 TFLOPS. The MI455X adds an FP16 figure of 157.3 TFLOPS with a 1:1 ratio, which the MI300A lacks. Texture rate increases from 1,915.2 GTexel/s to 2,457.6 GTexel/s, a 28.3% difference.

TDP rises from 750 W to 2300 W, and suggested PSU from 1150 W to 2700 W. The form factor changes from OAM Module to EAM Module. The bus interface moves from PCIe 5.0 x16 to PCIe 6.0 x16. Both have no power connectors, no display outputs, and no recorded dimensions.

The MI300A was released on December 5, 2023, and the MI455X on July 22, 2026. Both have Radeon Instinct as their predecessor, and neither has a recorded successor. Neither part has a launch MSRP in the database.

Architecture Differences

The architectural gap between these two accelerators is substantial. The MI300A uses CDNA 3.0, while the MI455X uses CDNA 5.0, representing two full architectural generations. The chip designations differ as well: Aqua Vanjaram for the MI300A versus MI450 256CU for the MI455X.

The manufacturing process moves from TSMC's 5 nm node to its 2 nm node. This process shrink allows the MI455X to integrate 320,000 million transistors, more than double the MI300A's 153,000 million. The die grows to 2990 mm² from 1017 mm², and despite the larger die, transistor density falls from 150.4M per mm² to 107.0M per mm², indicating that the newer node does not pack transistors more densely in this design.

The compute architecture scales significantly. Shading units grow from 14,592 to 32,768, a 2.25x increase. Texture units grow more modestly from 912 to 1024, a 12.3% increase. This imbalance suggests the MI455X is more heavily optimized for compute throughput than texture-mapping workloads, consistent with its data center positioning.

Memory architecture changes fundamentally. The MI300A uses HBM3 with an 8192-bit bus, while the MI455X uses HBM4 with a 24576-bit bus. The bus width triples, and the effective memory clock rises from 5.2 Gbps to 7.6 Gbps. Combined, these changes produce the 4.38x bandwidth advantage. The memory capacity grows to 432 GB, which is 3.375x the MI300A's 128 GB.

The MI455X records FP16 at 157.3 TFLOPS with a 1:1 ratio to FP32. The MI300A has no FP16 entry in the database, leaving its half-precision capabilities unquantified. The FP32 scaling from 61.29 TFLOPS to 157.3 TFLOPS is a 2.57x increase, which exceeds the 2.25x shading unit scaling, implying higher per-shader efficiency in the CDNA 5.0 design.

The interface changes from PCIe 5.0 x16 to PCIe 6.0 x16, doubling the available host interconnect bandwidth per lane generation. Both accelerators are compute-only, with no graphics APIs supported and no display outputs. The MI455X's 2300 W TDP and 2700 W suggested power supply reflect a design that prioritizes absolute throughput over power efficiency, whereas the MI300A's 750 W TDP with 1150 W suggested PSU fits into more conventional server power budgets.