AMD Instinct MI355X vs AMD Radeon Instinct MI308X Comparison

Head-to-Head Benchmarks

The recorded database contains no benchmark scores for either the AMD Instinct MI355X or the AMD Radeon Instinct MI308X. Both entries show an average benchmark score of zero, and no head-to-head benchmark results are listed. The percentile versus all GPUs for both is 50, placing them at the median of the recorded field, though this is a default position given the absence of measured data.

What can be compared directly from the specification sheets are the raw compute ceilings. The MI355X delivers 78.64 TFLOPS of FP32, while the MI308X delivers 81.72 TFLOPS. The MI308X holds a 3.08 TFLOPS lead in FP32, which is roughly 3.9% higher based on the recorded figures. In FP16, the disparity is far larger. The MI308X lists 653.7 TFLOPS with an 8:1 ratio, while the MI355X lists 78.64 TFLOPS with a 1:1 ratio. That means the MI308X has a massive FP16 advantage on paper, over 8 times the throughput when the ratio is considered.

Texture rate also favors the MI308X. The MI308X records 2,553.6 GTexel/s versus the MI355X's 2,457.6 GTexel/s, a difference of 96 GTexel/s. Both GPUs list a pixel rate of 0 MPixel/s, which reflects their compute-focused design with no raster output units.

Memory bandwidth tells a different story. The MI355X records 8.19 TB/s, while the MI308X records 10.3 TB/s. The MI308X holds a 2.11 TB/s bandwidth advantage. However, the MI355X has 288 GB of HBM3e memory compared to the MI308X's 192 GB of HBM3. The MI355X offers 96 GB more capacity, a 50% increase in memory size.

The boost clocks differ by 300 MHz. The MI355X boosts to 2400 MHz, while the MI308X boosts to 2100 MHz. Base clocks are identical at 1000 MHz. The MI355X achieves its memory clock at 2000 MHz with 8 Gbps effective, while the MI308X runs memory at 2525 MHz with 10.1 Gbps effective.

Where Each One Wins

The MI308X wins in raw FP32 compute, FP16 throughput, texture rate, and memory bandwidth. Its FP32 figure of 81.72 TFLOPS exceeds the MI355X's 78.64 TFLOPS. The FP16 figure of 653.7 TFLOPS far exceeds the MI355X's 78.64 TFLOPS, making the MI308X the clear choice for workloads that rely on reduced-precision arithmetic, assuming the 8:1 ratio applies to the intended operations.

The MI355X wins in memory capacity, process node, transistor count, die size, and power efficiency targets. The 288 GB capacity versus 192 GB means larger models or datasets can reside on the GPU without spilling to host memory. The MI355X uses a 3 nm process from TSMC, while the MI308X uses a 5 nm process. The MI355X packs 185,000 million transistors on a 2380 mm² die, compared to 153,000 million transistors on a 1017 mm² die for the MI308X.

The MI355X has a lower transistor density of 77.7 million transistors per mm², versus 150.4 million per mm² for the MI308X. This suggests the MI355X uses its larger die area differently, possibly for the expanded memory capacity and HBM3e stacks. The MI308X crams more transistors into a smaller area, which aligns with its higher FP16 throughput.

Power draw is not a direct performance metric, but the TDP figures are recorded. The MI355X lists a 1400 W TDP with a suggested PSU of 1800 W. The MI308X lists a 750 W TDP with a suggested PSU of 1150 W. The MI308X delivers higher FP32 and FP16 throughput while drawing 650 W less, based on the recorded TDP values. This makes the MI308X the more compute-per-watt option in the database. The MI355X compensates with memory capacity and a newer architecture.

Architecture Differences

The MI355X uses CDNA 4.0 architecture, while the MI308X uses CDNA 3.0. This is a generational gap within AMD's Instinct line. The MI355X is part of the Instinct (MIx) generation, while the MI308X is part of the Radeon Instinct (MIx) generation. The chip names differ as well: the MI355X uses the "MI350 256CU" chip, and the MI308X uses "Aqua Vanjaram."

The process node difference is significant. The MI355X is built on TSMC's 3 nm process, while the MI308X uses TSMC's 5 nm process. The transistor counts reflect the node and die size: 185,000 million on 2380 mm² for the MI355X, and 153,000 million on 1017 mm² for the MI308X. The MI308X has a higher transistor density at 150.4 million per mm², versus 77.7 million per mm² for the MI355X.

Memory architecture diverges. The MI355X uses HBM3e across a 8192-bit bus, delivering 8.19 TB/s. The MI308X uses HBM3 across an equally wide 8192-bit bus, delivering 10.3 TB/s. The MI355X has 288 GB, the MI308X has 192 GB. The memory clock for the MI355X is 2000 MHz with 8 Gbps effective, while the MI308X runs at 2525 MHz with 10.1 Gbps effective.

Shader core counts differ. The MI355X has 16,384 shading units and 1,024 texture mapping units. The MI308X has 19,456 shading units and 1,216 TMUs. The MI355X has no recorded ROPs, and neither does the MI308X, consistent with compute accelerators lacking traditional display output. Both use a PCIe 5.0 x16 bus interface, and both have no display outputs.

The MI355X lists no API support for DirectX, OpenGL, or Vulkan. The MI308X lists null values for these APIs. Both are OAM modules with no power connectors, relying on the module slot for power delivery. The MI355X has dimensions of 102 mm length and 165 mm width. The MI308X has no recorded dimensions.

Release dates differ. The MI355X was released on June 11, 2025. The MI308X was released on December 5, 2023. The MI355X lists its predecessor as "Radeon Instinct," while the MI308X lists its predecessor as "FirePro Data Center." Neither has a recorded successor.

FAQ

Q: Which GPU has more memory capacity?

A: The AMD Instinct MI355X has 288 GB of HBM3e, while the AMD Radeon Instinct MI308X has 192 GB of HBM3. The MI355X offers 96 GB more capacity.

Q: Which GPU has higher FP32 throughput?

A: The AMD Radeon Instinct MI308X records 81.72 TFLOPS of FP32, exceeding the AMD Instinct MI355X's 78.64 TFLOPS.

Q: What is the memory bandwidth difference?

A: The MI308X records 10.3 TB/s, and the MI355X records 8.19 TB/s. The MI308X has a 2.11 TB/s advantage.

Q: What process nodes are used?

A: The MI355X uses TSMC's 3 nm process. The MI308X uses TSMC's 5 nm process.

Q: What are the TDP figures?

A: The MI355X has a TDP of 1400 W with a suggested PSU of 1800 W. The MI308X has a TDP of 750 W with a suggested PSU of 1150 W.

Q: What is the FP16 performance of each?

A: The MI308X records 653.7 TFLOPS at an 8:1 ratio. The MI355X records 78.64 TFLOPS at a 1:1 ratio. The MI308X's FP16 figure is substantially higher.

Specification Differences

| Field | AMD Instinct MI355X | AMD Radeon Instinct MI308X |

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

| Chip | MI350 256CU | Aqua Vanjaram |

| Architecture | CDNA 4.0 | CDNA 3.0 |

| Generation | Instinct (MIx) | Radeon Instinct (MIx) |

| 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 | 16,384 | 19,456 |

| TMUs | 1,024 | 1,216 |

| 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 length, 165 mm width | Not recorded |

| Release Date | June 11, 2025 | December 5, 2023 |

| Predecessor | Radeon Instinct | FirePro Data Center |

Fields not listed above, including base clock (1000 MHz for both), bus width (8192 bit for both), bus interface (PCIe 5.0 x16 for both), display outputs (none for both), pixel rate (0 MPixel/s for both), slot width (OAM Module for both), power connectors (none for both), and API support (N/A or null), are identical or equivalent between the two.

The Verdict

The data indicates a clear split in strengths. The AMD Radeon Instinct MI308X is the stronger compute engine for FP32 and FP16 workloads. Its 81.72 TFLOPS FP32 and 653.7 TFLOPS FP16 figures, combined with a 750 W TDP, make it the higher-throughput and lower-power option in the database. It also has higher memory bandwidth at 10.3 TB/s and a higher texture rate at 2,553.6 GTexel/s.

The AMD Instinct MI355X is the newer design, released on June 11, 2025 versus December 5, 2023 for the MI308X. It uses CDNA 4.0 on a 3 nm node, packs 185,000 million transistors, and carries 288 GB of HBM3e. Its FP32 and FP16 figures are lower than the MI308X, but its memory capacity is 50% larger.

Users who need maximum memory capacity for large working sets would select the MI355X. Users who need peak FP32 or FP16 throughput, or who want lower power draw, would select the MI308X. The MI308X delivers more compute per watt from the recorded TDP values, while the MI355X delivers more memory per GPU. The absence of benchmark scores means these conclusions rest entirely on the specification sheets in the database.