AMD Instinct MI355X vs AMD Radeon Instinct MI300A Comparison

Head-to-Head Benchmarks

The recorded data shows no benchmark scores for either the AMD Instinct MI355X or the AMD Radeon Instinct MI300A. Both entries carry an average benchmark score of 0 and a percentile rank of 50 against all GPUs, meaning the database contains no direct performance measurements for either accelerator. Without head-to-head benchmark results, the comparison relies entirely on the architectural specifications and theoretical compute figures recorded in the database.

The FP32 compute figures show a narrow gap. The MI355X delivers 78.64 TFLOPS, while the MI300A reaches 81.72 TFLOPS, placing the older part approximately 3.9% ahead in single-precision floating-point throughput. This is a modest advantage, and it stems from the MI300A's larger shader array. The MI300A packs 19,456 shading units compared to the MI355X's 16,384, and 1,216 texture mapping units versus 1,024. Despite the MI355X's higher boost clock of 2400 MHz against 2100 MHz, the raw unit count on the MI300A overcomes the frequency deficit.

The FP16 picture reverses dramatically. The MI355X records 78.64 TFLOPS at a 1:1 ratio, meaning its FP16 throughput equals its FP32 throughput. The MI300A records 653.7 TFLOPS at an 8:1 ratio, meaning it uses eight FP16 operations per FP32 operation. This gives the MI300A an 8.3x advantage in peak FP16 compute, a massive difference that reflects the two architectures' different approaches to matrix math. The MI300A's CDNA 3.0 design clearly prioritizes dense FP16 throughput for AI training workloads, while the MI355X's CDNA 4.0 architecture appears to emphasize balanced FP32 and FP16 capabilities.

Texture rate also favors the MI300A. The older part achieves 2,553.6 GTexel/s against the MI355X's 2,457.6 GTexel/s, a 3.9% difference that aligns with the FP32 gap. Both parts record 0 MPixel/s pixel rates, a common trait for compute-focused accelerators that lack traditional raster output units. Neither card has any display outputs, reinforcing their purpose as dedicated data center compute modules.

Where Each One Wins

The MI300A wins in raw FP32 throughput, raw FP16 throughput, and texture fill rate. Its 19,456 shading units provide a structural advantage in any workload that scales with shader count, and the 8:1 FP16 ratio makes it the clear choice for peak half-precision math. The database shows the MI300A also has higher memory bandwidth at 10.3 TB/s against the MI355X's 8.19 TB/s, and a faster effective memory clock at 10.1 Gbps versus 8 Gbps. This suggests the MI300A can feed its compute units more quickly, which matters for bandwidth-bound operations.

The MI355X wins in capacity and efficiency of implementation. It carries 288 GB of HBM3e memory versus 192 GB of HBM3, a 50% capacity increase. This allows larger models and datasets to reside on the accelerator without spilling to host memory. The MI355X also runs at a higher boost clock, 2400 MHz versus 2100 MHz, and uses a smaller 3 nm process node compared to the MI300A's 5 nm. The newer node enables higher transistor density, 77.7M per mm² versus 150.4M per mm² on the older part, although the MI355X's die is much larger at 2380 mm² against 1017 mm².

For power efficiency, the MI355X consumes 1400 W TDP, while the MI300A consumes 750 W. The newer part uses nearly twice the power budget, which means its FP32 performance per watt is lower in absolute terms. The MI300A delivers 81.72 TFLOPS at 750 W, roughly 0.109 TFLOPS per watt, while the MI355X delivers 78.64 TFLOPS at 1400 W, roughly 0.056 TFLOPS per watt. The MI300A is the more power-efficient FP32 performer in the recorded specifications.

Architecture Differences

The two accelerators come from different generations of AMD's CDNA architecture. The MI355X uses CDNA 4.0 and is built on a 3 nm process at TSMC, while the MI300A uses CDNA 3.0 and is built on a 5 nm process at the same foundry. The MI355X uses the MI350 256CU chip, while the MI300A uses the Aqua Vanjaram chip.

Transistor counts differ significantly. The MI355X integrates 185,000 million transistors on a 2380 mm² die, yielding a density of 77.7M per mm². The MI300A integrates 153,000 million transistors on a 1017 mm² die, yielding a density of 150.4M per mm². The MI300A is far denser despite being on an older node, because the MI355X's larger die spreads the transistors thinner. The MI355X has 8,192 additional shading units worth of potential compute, but it does not use them for higher FP32 output.

Memory subsystems differ in both capacity and type. The MI355X uses HBM3e with 288 GB capacity, an 8192-bit bus, and 8.19 TB/s bandwidth. The MI300A uses HBM3 with 192 GB capacity, also an 8192-bit bus, but higher bandwidth at 10.3 TB/s. The MI355X runs its memory at 2000 MHz with 8 Gbps effective speed, while the MI300A runs at 2525 MHz with 10.1 Gbps effective speed. The newer part trades bandwidth for capacity, offering 50% more memory but 20% less throughput.

Clock speeds show the MI355X with a 1000 MHz base and 2400 MHz boost, against the MI300A's 1000 MHz base and 2100 MHz boost. The 300 MHz boost advantage helps the MI355X close some of the gap in FP32, but not enough to overtake the MI300A's larger shader count. Both parts are OAM modules with PCIe 5.0 x16 interfaces, no power connectors (power delivered via the OAM socket), and no display outputs.

The FP16 ratio difference is the most striking architectural divergence. The MI355X records FP16 at 1:1, meaning it processes half-precision at the same rate as full-precision. The MI300A records FP16 at 8:1, meaning it processes eight half-precision operations for every full-precision operation. This is a fundamental design choice: CDNA 3.0 optimized for matrix-heavy FP16 workloads, while CDNA 4.0 appears to prioritize FP32 throughput and possibly newer formats not listed in the database.

FAQ

Q: Which accelerator has higher FP32 compute?

A: The MI300A leads with 81.72 TFLOPS against the MI355X's 78.64 TFLOPS, a 3.9% advantage.

Q: How do the FP16 capabilities compare?

A: The MI300A delivers 653.7 TFLOPS at an 8:1 ratio, while the MI355X delivers 78.64 TFLOPS at a 1:1 ratio. The MI300A has 8.3x higher peak FP16 throughput.

Q: Which part has more memory capacity?

A: The MI355X has 288 GB of HBM3e, while the MI300A has 192 GB of HBM3. The MI355X offers 50% more capacity.

Q: Which part has higher memory bandwidth?

A: The MI300A reaches 10.3 TB/s, while the MI355X reaches 8.19 TB/s. The MI300A has a 25.8% bandwidth advantage.

Q: What are the process nodes for each accelerator?

A: The MI355X uses a 3 nm process at TSMC, while the MI300A uses a 5 nm process at TSMC.

Q: What is the power consumption difference?

A: The MI355X has a 1400 W TDP and a suggested PSU of 1800 W. The MI300A has a 750 W TDP and a suggested PSU of 1150 W.

Specification Differences

| Field | AMD Instinct MI355X | AMD Radeon Instinct MI300A |

|---|---|---|

| Chip | MI350 256CU | Aqua Vanjaram |

| Architecture | CDNA 4.0 | CDNA 3.0 |

| Process Node | 3 nm | 5 nm |

| Transistors | 185,000 million | 153,000 million |

| Die Size | 2380 mm² | 1017 mm² |

| Transistor Density | 77.7M / mm² | 150.4M / mm² |

| Boost Clock | 2400 MHz | 2100 MHz |

| Memory Clock | 2000 MHz, 8 Gbps effective | 2525 MHz, 10.1 Gbps effective |

| Memory Size | 288 GB | 192 GB |

| Memory Type | HBM3e | HBM3 |

| Memory Bandwidth | 8.19 TB/s | 10.3 TB/s |

| Shading Units | 16384 | 19456 |

| TMUs | 1024 | 1216 |

| Texture Rate | 2,457.6 GTexel/s | 2,553.6 GTexel/s |

| FP32 | 78.64 TFLOPS | 81.72 TFLOPS |

| FP16 | 78.64 TFLOPS (1:1) | 653.7 TFLOPS (8:1) |

| TDP | 1400 W | 750 W |

| Suggested PSU | 1800 W | 1150 W |

| Dimensions | 102 mm x 165 mm | Not recorded |

| Release Date | 2025-06-11 | 2023-12-05 |

| Predecessor | Radeon Instinct | FirePro Data Center |

Both parts share the same base clock (1000 MHz), memory bus width (8192 bit), pixel rate (0 MPixel/s), slot width (OAM Module), power connectors (None), bus interface (PCIe 5.0 x16), and display outputs (No outputs). The MI300A records no API support entries, while the MI355X lists DirectX, OpenGL, and Vulkan as N/A. The MI300A's dimensions are not recorded in the database. The MI355X has a later release date by approximately 18 months, and its predecessor is listed as Radeon Instinct, whereas the MI300A's predecessor is FirePro Data Center.