AMD Instinct MI355X vs NVIDIA Rubin GPU Comparison

The Verdict

The database records two distinct server accelerators with no direct benchmark overlap, making a performance winner impossible to declare from measured results. The AMD Instinct MI355X and NVIDIA Rubin GPU occupy the same 288 GB memory class but diverge sharply in architecture and execution strategy. The data indicates the MI355X targets workloads that favor raw FP32 throughput and massive texture processing, while the Rubin GPU prioritizes FP16 compute and memory bandwidth at a significantly higher power envelope. Neither device shows a benchmark advantage over the other because the recorded benchmark arrays are empty for both entries. The MI355X presents a 3 nm design with a 1000 MHz base clock and 2400 MHz boost, while the Rubin GPU operates at a 700 MHz base and 2267 MHz boost, suggesting different thermal and power design points. For buyers, the choice hinges on software ecosystem and specific compute ratios rather than measured performance, as the database shows no head-to-head results. The MI355X uses CDNA 4.0 architecture with a 256 CU chip, while the Rubin GPU uses the GR100 chip with a Rubin architecture, indicating different instruction sets and optimization targets. The Rubin GPU's 2:1 FP16 to FP32 ratio versus the MI355X's 1:1 ratio points to different intended precision profiles.

Architecture Differences

The MI355X employs the CDNA 4.0 architecture built on a 3 nm process at TSMC, featuring the MI350 256CU chip. The Rubin GPU uses a Rubin architecture on the same 3 nm TSMC process but with the GR100 chip. Transistor counts differ substantially: the MI355X integrates 185,000 million transistors on a 2380 mm² die, while the Rubin GPU packs 336,000 million transistors into a 1456 mm² die. This yields a transistor density of 77.7M per mm² for the MI355X versus 230.8M per mm² for the Rubin GPU, indicating a much denser packing on the NVIDIA side. The MI355X uses HBM3e memory with an 8192 bit bus, while the Rubin GPU uses HBM4 with a 16384 bit bus, doubling the memory interface width.

Shading unit counts diverge: the MI355X has 16,384 shading units and 1,024 texture mapping units, while the Rubin GPU has 28,672 shading units and 896 TMUs. The Rubin GPU also includes 896 tensor cores and 24 ROPs, whereas the MI355X reports 0 ROPs and no tensor core field. The MI355X delivers a texture rate of 2,457.6 GTexel/s against the Rubin GPU's 2,031.2 GTexel/s, despite the latter having more shading units. Pixel rates tell a different story: the MI355X reports 0 MPixel/s, while the Rubin GPU delivers 54.41 GPixel/s. Both devices have no display outputs and no DirectX, OpenGL, or Vulkan API support, confirming their server-only orientation.

The MI355X uses a PCIe 5.0 x16 interface, while the Rubin GPU uses PCIe 6.0 x16. Power delivery differs markedly: the MI355X has a 1400 W TDP with no power connectors (OAM Module slot width), while the Rubin GPU has a 2300 W TDP with a SXM Module slot width. The suggested PSU ratings are 1800 W for the MI355X and 2700 W for the Rubin GPU. The MI355X measures 102 mm in length and 165 mm in width, while the Rubin GPU has no recorded dimensions. The MI355X has a release date of 2025-06-11, and the Rubin GPU follows on 2025-12-31. The MI355X's predecessor is Radeon Instinct, while the Rubin GPU's predecessor is Server Blackwell. The Rubin GPU carries an "Active" production status, while the MI355X's status is not recorded.

Head-to-Head Benchmarks

The database contains no head-to-head benchmark entries for these two accelerators. The winsA and winsB counters both read 0, and the headToHeadBenchmarks array is empty. Consequently, no direct performance comparisons can be drawn from measured results. The MI355X has an average benchmark score of 0 and a percentile vs all GPUs of 50, matching the Rubin GPU's identical 0 score and 50th percentile. Without recorded benchmark data, the analysis must rely on architectural specifications and compute ratios.

The MI355X delivers 78.64 TFLOPS FP32 and 78.64 TFLOPS FP16 (1:1 ratio). The Rubin GPU outputs 130.0 TFLOPS FP32 and 260.0 TFLOPS FP16 (2:1 ratio). This means the Rubin GPU achieves 65.3% higher FP32 throughput and 230.6% higher FP16 throughput compared to the MI355X, based purely on the recorded specification values. Memory bandwidth favors the Rubin GPU at 22.1 TB/s versus 8.19 TB/s for the MI355X, a 169.8% advantage. The MI355X's texture rate of 2,457.6 GTexel/s exceeds the Rubin GPU's 2,031.2 GTexel/s by 21.0%. The Rubin GPU's pixel rate of 54.41 GPixel/s contrasts with the MI355X's 0 MPixel/s, though neither device has display outputs, making pixel rate largely irrelevant for compute workloads.

Clock speeds show the MI355X running at 1000 MHz base and 2400 MHz boost, against the Rubin GPU's 700 MHz base and 2267 MHz boost. The MI355X's memory runs at 2000 MHz (8 Gbps effective), while the Rubin GPU's memory operates at 2695 MHz (10.8 Gbps effective). The Rubin GPU's 16384 bit bus width is double the MI355X's 8192 bit width, which explains its superior bandwidth despite the narrower relative clock advantage. The MI355X's higher boost clock (2400 MHz vs 2267 MHz) partially compensates for its lower shading unit count in texture operations, as evidenced by its higher texture rate.

Specification Differences

| Specification | AMD Instinct MI355X | NVIDIA Rubin GPU |

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

| Chip | MI350 256CU | GR100 |

| Architecture | CDNA 4.0 | Rubin |

| Generation | Instinct (MIx) | Server Rubin (Rxx) |

| Process Node | 3 nm | 3 nm |

| Transistors | 185,000 million | 336,000 million |

| Die Size | 2380 mm² | 1456 mm² |

| Transistor Density | 77.7M / mm² | 230.8M / mm² |

| Base Clock | 1000 MHz | 700 MHz |

| Boost Clock | 2400 MHz | 2267 MHz |

| Memory Clock | 2000 MHz 8 Gbps effective | 2695 MHz 10.8 Gbps effective |

| Memory Type | HBM3e | HBM4 |

| Memory Bus Width | 8192 bit | 16384 bit |

| Memory Bandwidth | 8.19 TB/s | 22.1 TB/s |

| Shading Units | 16384 | 28672 |

| TMUs | 1024 | 896 |

| ROPs | 0 | 24 |

| Tensor Cores | Not recorded | 896 |

| Pixel Rate | 0 MPixel/s | 54.41 GPixel/s |

| Texture Rate | 2,457.6 GTexel/s | 2,031.2 GTexel/s |

| FP32 | 78.64 TFLOPS | 130.0 TFLOPS |

| FP16 | 78.64 TFLOPS (1:1) | 260.0 TFLOPS (2:1) |

| TDP | 1400 W | 2300 W |

| Slot Width | OAM Module | SXM Module |

| Suggested PSU | 1800 W | 2700 W |

| Bus Interface | PCIe 5.0 x16 | PCIe 6.0 x16 |

| Release Date | 2025-06-11 | 2025-12-31 |

| Predecessor | Radeon Instinct | Server Blackwell |

| Production Status | Not recorded | Active |

| Dimensions | 102 mm length, 165 mm width | Not recorded |

FAQ

Q: Which GPU has higher FP32 compute performance?

A: The NVIDIA Rubin GPU delivers 130.0 TFLOPS FP32, which is 65.3% higher than the AMD Instinct MI355X's 78.64 TFLOPS FP32.

Q: How do the memory systems compare?

A: The Rubin GPU uses HBM4 with a 16384 bit bus and achieves 22.1 TB/s bandwidth, while the MI355X uses HBM3e with an 8192 bit bus and achieves 8.19 TB/s. The Rubin GPU's bandwidth is 169.8% higher.

Q: What is the FP16 performance difference?

A: The Rubin GPU delivers 260.0 TFLOPS FP16 (2:1 ratio), which is 230.6% higher than the MI355X's 78.64 TFLOPS FP16 (1:1 ratio).

Q: Which accelerator has a higher boost clock?

A: The MI355X has a boost clock of 2400 MHz, compared to the Rubin GPU's 2267 MHz, a difference of 133 MHz in favor of the AMD part.

Q: What are the power requirements for each?

A: The MI355X has a 1400 W TDP with a suggested PSU of 1800 W, while the Rubin GPU has a 2300 W TDP with a suggested PSU of 2700 W.

Q: Are these devices compatible with display outputs?

A: No, both the MI355X and Rubin GPU have no display outputs and no DirectX, OpenGL, or Vulkan API support, confirming their server-only design.

Where Each One Wins

The AMD Instinct MI355X wins in texture processing, with a texture rate of 2,457.6 GTexel/s versus the Rubin GPU's 2,031.2 GTexel/s. This 21.0% advantage, combined with its higher boost clock of 2400 MHz, suggests the MI355X is better suited for workloads that depend on texture sampling and filtering operations. Its lower TDP of 1400 W versus 2300 W also makes it a more power-efficient option per watt, though the database does not record performance per watt metrics. The MI355X's 1:1 FP16 to FP32 ratio indicates it treats both precisions equally, which could benefit mixed-precision workloads that require consistent throughput across formats. Its PCIe 5.0 x16 interface, while older than the Rubin GPU's PCIe 6.0 x16, remains compatible with existing server infrastructure.

The NVIDIA Rubin GPU wins decisively in FP16 compute, delivering 260.0 TFLOPS versus the MI355X's 78.64 TFLOPS. Its 2:1 FP16 to FP32 ratio indicates a design optimized for AI training and inference workloads that heavily leverage reduced precision. The Rubin GPU also wins on memory bandwidth at 22.1 TB/s, a 169.8% advantage over the MI355X, which benefits memory-bound operations such as large model parameter updates and data streaming. Its 28,672 shading units and 896 tensor cores provide substantially more parallel execution resources than the MI355X's 16,384 shading units. The Rubin GPU's 130.0 TFLOPS FP32 output also exceeds the MI355X's 78.64 TFLOPS, giving it a 65.3% edge in single-precision compute. The 16384 bit memory bus allows the Rubin GPU to feed its larger compute units more effectively. Its PCIe 6.0 x16 interface provides newer interconnect technology for multi-GPU communication. The Rubin GPU's 54.41 GPixel/s pixel rate, while irrelevant for compute-only servers, indicates the hardware can perform rasterization if ever needed, though no display outputs exist. Its higher transistor count of 336,000 million and density of 230.8M per mm² suggest a more complex and potentially more capable design, though the database records no benchmark scores to confirm this. The Rubin GPU's later release date of 2025-12-31 gives it additional time for software optimization and ecosystem maturity compared to the MI355X's 2025-06-11 release.