AMD Instinct MI455X vs NVIDIA H800 SXM5 Comparison

Head-to-Head Benchmarks

The recorded database contains no direct head-to-head benchmark comparisons between the AMD Instinct MI455X and the NVIDIA H800 SXM5. Neither processor has any benchmark entries listed in the database, and both hold an identical percentile rank of 50 against all GPUs. Their average benchmark scores are both recorded as zero. Consequently, the head-to-head analysis must rely entirely on the architectural and specification data available, since no measured performance scores exist to compare.

The most decisive difference in the recorded data is raw compute throughput. The AMD Instinct MI455X delivers 157.3 TFLOPS of FP32 performance, which is 2.65 times the 59.30 TFLOPS recorded for the NVIDIA H800 SXM5. In FP16 operations, the comparison shifts: the AMD part again lists 157.3 TFLOPS at a 1:1 ratio, while the NVIDIA part reaches 237.2 TFLOPS at a 4:1 ratio. This means the H800 SXM5 holds a 1.51 times advantage in FP16 throughput, assuming the 4:1 ratio applies to its tensor operations. The MI455X, however, offers FP16 at a 1:1 ratio, which indicates the same throughput as FP32, a configuration that favors workloads requiring consistent precision without the reduced-rate penalty.

Memory capacity and bandwidth heavily favor the AMD part. The MI455X carries 432 GB of HBM4 memory across a 24576-bit bus, producing 23.3 TB/s of bandwidth. The H800 SXM5 has 80 GB of HBM3 memory on a 5120-bit bus, yielding 3.36 TB/s. The MI455X therefore provides 5.4 times the memory capacity and 6.93 times the memory bandwidth. These are not marginal differences; they represent different classes of memory subsystem capability.

Texture throughput also favors AMD. The MI455X records 2,457.6 GTexel/s, while the H800 SXM5 records 926.6 GTexel/s, a 2.65 times advantage. Pixel rate, however, is effectively absent on the AMD part at 0 MPixel/s, whereas the H800 SXM5 records 42.12 GPixel/s. This reflects their differing rasterization pipelines, with the NVIDIA part retaining some fixed-function output capability.

Clock behavior differs notably. The H800 SXM5 has a higher base clock at 1095 MHz versus 1000 MHz, but the MI455X has a much higher boost clock at 2400 MHz versus 1755 MHz. The AMD boost clock is 1.37 times higher, which aligns with its higher FP32 throughput per shading unit. Memory clocks also differ: the MI455X runs at 1900 MHz with 7.6 Gbps effective, while the H800 SXM5 runs at 1313 MHz with 5.3 Gbps effective.

FAQ

Q: Which processor has more FP32 compute throughput?

A: The AMD Instinct MI455X records 157.3 TFLOPS of FP32, which is 2.65 times the 59.30 TFLOPS of the NVIDIA H800 SXM5.

Q: Which processor provides more memory bandwidth?

A: The AMD Instinct MI455X provides 23.3 TB/s of bandwidth from its 432 GB HBM4 memory, which is 6.93 times the 3.36 TB/s of the NVIDIA H800 SXM5 with its 80 GB HBM3 memory.

Q: Does the NVIDIA H800 SXM5 lead in any compute metric?

A: Yes, in FP16 throughput the H800 SXM5 records 237.2 TFLOPS at a 4:1 ratio, which is 1.51 times the 157.3 TFLOPS of the MI455X at a 1:1 ratio.

Q: What are the transistor counts for each processor?

A: The AMD Instinct MI455X uses 320,000 million transistors on a 2990 mm² die with a 2 nm process, while the NVIDIA H800 SXM5 uses 80,000 million transistors on an 814 mm² die with a 5 nm process.

Q: What is the thermal design power for each processor?

A: The AMD Instinct MI455X is rated at 2300 W with a suggested power supply of 2700 W, while the NVIDIA H800 SXM5 is rated at 700 W with a suggested power supply of 1100 W.

Q: What is the memory type and bus width for each?

A: The MI455X uses HBM4 on a 24576-bit bus, while the H800 SXM5 uses HBM3 on a 5120-bit bus.

Architecture Differences

The two processors come from different architecture families. The AMD Instinct MI455X uses CDNA 5.0 architecture, built on a 2 nm process at TSMC with 320,000 million transistors on a 2990 mm² die. The transistor density works out to 107.0M per mm². The NVIDIA H800 SXM5 uses the Hopper architecture, built on a 5 nm process at TSMC with 80,000 million transistors on an 814 mm² die, giving a density of 98.3M per mm². The AMD chip therefore uses 4 times the transistor count and 3.67 times the die area.

The MI455X chip is designated MI450 256CU, indicating 256 compute units. It contains 32,768 shading units and 1,024 texture mapping units, with no ROPs recorded. The H800 SXM5 uses the GH100 chip, containing 16,896 shading units, 528 texture mapping units, and 24 ROPs. The AMD part also lists 528 tensor cores on the NVIDIA side, while the MI455X lists no tensor core count in the data.

Memory architecture differs substantially. The MI455X uses HBM4 with a 24576-bit bus and 432 GB capacity, while the H800 SXM5 uses HBM3 with a 5120-bit bus and 80 GB capacity. The AMD memory clock is 1900 MHz with 7.6 Gbps effective, versus 1313 MHz and 5.3 Gbps effective on the NVIDIA part. The MI455X provides 23.3 TB/s versus 3.36 TB/s.

The interface standards differ as well. The MI455X uses PCIe 6.0 x16, while the H800 SXM5 uses PCIe 5.0 x16. Both have no display outputs, and both list no API support: the AMD side explicitly records DirectX, OpenGL, and Vulkan as N/A, while the NVIDIA side records null values for those fields. The AMD part uses an EAM Module slot width with no power connectors, while the NVIDIA part uses an SXM Module with an 8-pin EPS connector. The suggested power supply ratings are 2700 W for AMD and 1100 W for NVIDIA.

The release timeline also separates them. The H800 SXM5 was released on 2023-03-20 and remains in active production, with its predecessor listed as Server Ada and its successor as Server Blackwell. The MI455X has a release date of 2026-07-22, with its predecessor listed as Radeon Instinct and no successor recorded.

The Verdict

The recorded data supports a clear split in suitability. The AMD Instinct MI455X is the stronger choice for workloads that depend on FP32 throughput, memory capacity, memory bandwidth, and texture processing. Its 157.3 TFLOPS FP32, 432 GB memory, and 23.3 TB/s bandwidth place it far ahead of the NVIDIA H800 SXM5 in these categories. The 2 nm process and PCIe 6.0 interface also indicate a newer platform generation.

The NVIDIA H800 SXM5 is the stronger choice for FP16-intensive workloads and for any scenario requiring a lower power envelope. Its 237.2 TFLOPS FP16 output exceeds the MI455X by a factor of 1.51, and its 700 W TDP is dramatically lower than the 2300 W TDP of the AMD part. The H800 SXM5 also has active production status and a longer market presence, with its release in 2023 versus the MI455X scheduled for 2026.

The data does not include any measured benchmark scores, so no comparison of real-world application performance is possible. The verdict must rest on the specification differences alone. The MI455X targets capacity and raw FP32 throughput; the H800 SXM5 targets FP16 efficiency and power-constrained deployment.

Specification Differences

| Specification | AMD Instinct MI455X | NVIDIA H800 SXM5 |

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

| Architecture | CDNA 5.0 | Hopper |

| Process Node | 2 nm | 5 nm |

| Transistors | 320,000 million | 80,000 million |

| Die Size | 2990 mm² | 814 mm² |

| Transistor Density | 107.0M / mm² | 98.3M / mm² |

| Base Clock | 1000 MHz | 1095 MHz |

| Boost Clock | 2400 MHz | 1755 MHz |

| Memory Clock | 1900 MHz, 7.6 Gbps effective | 1313 MHz, 5.3 Gbps effective |

| Memory Size | 432 GB | 80 GB |

| Memory Type | HBM4 | HBM3 |

| Memory Bus Width | 24576 bit | 5120 bit |

| Memory Bandwidth | 23.3 TB/s | 3.36 TB/s |

| Shading Units | 32768 | 16896 |

| TMUs | 1024 | 528 |

| ROPs | 0 | 24 |

| Tensor Cores | Not listed | 528 |

| Pixel Rate | 0 MPixel/s | 42.12 GPixel/s |

| Texture Rate | 2,457.6 GTexel/s | 926.6 GTexel/s |

| FP32 | 157.3 TFLOPS | 59.30 TFLOPS |

| FP16 | 157.3 TFLOPS (1:1) | 237.2 TFLOPS (4:1) |

| TDP | 2300 W | 700 W |

| Slot Width | EAM Module | SXM Module |

| Power Connectors | None | 8-pin EPS |

| Suggested PSU | 2700 W | 1100 W |

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

| Display Outputs | No outputs | No outputs |

| Release Date | 2026-07-22 | 2023-03-20 |

| Production Status | Not listed | Active |

Where Each One Wins

The AMD Instinct MI455X wins in FP32 compute, memory capacity, memory bandwidth, texture rate, and process technology. Its 157.3 TFLOPS FP32 is 2.65 times the H800 SXM5's 59.30 TFLOPS, making it the clear choice for FP32-heavy simulation, scientific computing, or any workload that relies on single-precision arithmetic. The 432 GB memory capacity is 5.4 times the 80 GB of the NVIDIA part, which matters for large model residency or big dataset processing. The 23.3 TB/s bandwidth is 6.93 times higher, which directly benefits memory-bound kernels. The 2 nm process node represents a newer manufacturing generation than the 5 nm node of the H800 SXM5.

The NVIDIA H800 SXM5 wins in FP16 throughput, pixel rate, power efficiency, and production readiness. Its 237.2 TFLOPS FP16 is 1.51 times the MI455X's 157.3 TFLOPS, which favors deep learning training and inference workloads that use mixed precision. The 42.12 GPixel/s pixel rate, while modest, is infinitely higher than the 0 MPixel/s recorded for the AMD part, indicating some rasterization output capability. The 700 W TDP versus 2300 W means the H800 SXM5 can be deployed in far more power-constrained environments, with a suggested PSU of 1100 W versus 2700 W. The active production status and earlier release date also indicate availability, whereas the MI455X has no recorded production status and a future release date.