AMD Instinct MI355X vs NVIDIA RTX A400 Comparison

FAQ

Q: What are the core architecture differences between the AMD Instinct MI355X and the NVIDIA RTX A400?

A: The MI355X uses AMD’s CDNA 4.0 architecture on a 3 nm TSMC process with 185,000 million transistors on a 2380 mm² die. The RTX A400 uses NVIDIA’s Ampere architecture on an 8 nm Samsung process with 8,700 million transistors on a 200 mm² die.

Q: How do the memory subsystems compare?

A: The MI355X features 288 GB of HBM3e memory on an 8192-bit bus with 8.19 TB/s bandwidth. The RTX A400 has 4 GB of GDDR6 on a 64-bit bus with 96.00 GB/s bandwidth.

Q: What is the compute performance difference in FP32 and FP16?

A: The MI355X delivers 78.64 TFLOPS for both FP32 and FP16 (1:1). The RTX A400 delivers 2.706 TFLOPS for both FP32 and FP16 (1:1).

Q: What are the power requirements for each card?

A: The MI355X has a TDP of 1400 W with a suggested PSU of 1800 W. The RTX A400 has a TDP of 50 W with a suggested PSU of 250 W.

Q: Which card supports display outputs?

A: The RTX A400 provides 4x mini-DisplayPort 1.4a outputs. The MI355X has no display outputs.

Q: What is the RTX A400’s benchmark standing relative to its nearest rivals?

A: The RTX A400 has an average benchmark score of 6078, placing it at the 35th percentile of all GPUs. Its nearest rival, the NVIDIA GeForce MX230, scores 6077 with a 0% delta, while the AMD Radeon 760M scores 6019 with a 1% delta.

The Verdict

The data presents two fundamentally distinct products. The AMD Instinct MI355X is an accelerator module designed for massive compute workloads, evidenced by its 288 GB HBM3e memory, 8.19 TB/s bandwidth, and 78.64 TFLOPS FP32 throughput. Its 1400 W TDP and OAM Module form factor indicate a data-center-class part with no display output.

The NVIDIA RTX A400 is a workstation graphics card with 4 GB GDDR6, 96.00 GB/s bandwidth, and 2.706 TFLOPS FP32. It supports four mini-DisplayPort outputs and fits in a single slot with a 50 W TDP. Its benchmark scores show it competing closely with entry-level mobile and integrated GPUs.

For users requiring compute density, massive memory capacity, and accelerator-class bandwidth, the MI355X is the clear choice. For workstation visualization, multi-display setups, and low-power operation, the RTX A400 serves that role. The two products do not directly compete; the MI355X targets compute clusters, while the RTX A400 targets professional desktop use.

Architecture Differences

The MI355X uses the CDNA 4.0 architecture, which is AMD’s compute-optimized design lineage. It is built on a 3 nm process at TSMC, hosting 185,000 million transistors on a 2380 mm² die. The transistor density is 77.7M per mm². The chip is designated MI350 256CU, indicating a 256 compute unit configuration.

The RTX A400 uses the Ampere architecture, specifically the GA107 chip, built on Samsung’s 8 nm process. It contains 8,700 million transistors on a 200 mm² die, yielding a transistor density of 43.5M per mm². Ampere is a unified graphics and compute architecture, supporting DirectX 12 Ultimate (12_2), OpenGL 4.6, and Vulkan 1.4.

The MI355X has no listed API support for DirectX, OpenGL, or Vulkan, reinforcing its compute-only orientation. The RTX A400 includes 6 ray tracing cores and 24 tensor cores, features absent from the MI355X’s specification sheet. The MI355X has 0 ROPs and a 0 MPixel/s pixel rate, while the RTX A400 has 16 ROPs and a 28.19 GPixel/s pixel rate.

Texture processing differs sharply: the MI355X delivers 2,457.6 GTexel/s from 1024 TMUs, whereas the RTX A400 delivers 42.29 GTexel/s from 24 TMUs. Shading units number 16,384 on the MI355X versus 768 on the RTX A400.

Specification Differences

The MI355X and RTX A400 differ across nearly every hardware field. The MI355X operates at a base clock of 1000 MHz and boost clock of 2400 MHz. The RTX A400 has a higher base clock of 1417 MHz but a lower boost clock of 1762 MHz. Memory clocks are 2000 MHz (8 Gbps effective) for the MI355X and 1500 MHz (12 Gbps effective) for the RTX A400.

Memory capacity and type are fundamentally different: 288 GB HBM3e on a 8192-bit bus versus 4 GB GDDR6 on a 64-bit bus. Bandwidth is 8.19 TB/s versus 96.00 GB/s, a difference of roughly 85 times.

The MI355X has no power connectors and uses an OAM Module slot width. The RTX A400 is single-slot with no power connectors. Suggested PSUs are 1800 W and 250 W respectively. The MI355X uses PCIe 5.0 x16, while the RTX A400 uses PCIe 4.0 x8.

Physical dimensions: the MI355X is 102 mm long and 165 mm wide. The RTX A400 is 163 mm long and 69 mm high. The MI355X has no display outputs; the RTX A400 has 4x mini-DisplayPort 1.4a.

Release dates differ: the MI355X launched on 2025-06-11, while the RTX A400 launched on 2024-04-15. The MI355X’s predecessor is Radeon Instinct, and the RTX A400’s predecessor is Quadro Turing with a successor of Workstation Ada. The RTX A400 has an active production status; the MI355X’s status is not listed.

Head-to-Head Benchmarks

The head-to-head benchmark dataset is empty, so direct comparison relies on the recorded specifications and the RTX A400’s individual benchmark scores.

In FP32 compute, the MI355X delivers 78.64 TFLOPS versus the RTX A400’s 2.706 TFLOPS. This represents a 29-fold advantage for the MI355X. The same ratio applies to FP16, where both cards offer a 1:1 ratio relative to their FP32 figures.

Memory bandwidth shows the largest gap: 8.19 TB/s versus 96.00 GB/s. The MI355X’s 288 GB capacity is 72 times the RTX A400’s 4 GB. The bus width difference, 8192-bit versus 64-bit, is 128 times.

Texture fill rate favors the MI355X at 2,457.6 GTexel/s versus 42.29 GTexel/s. Pixel fill rate favors the RTX A400, which has a measurable 28.19 GPixel/s, while the MI355X is listed at 0 MPixel/s.

The RTX A400’s benchmark results show a Geekbench OpenCL score of 22844 and a Vulkan score of 22237. Its Passmark scores are 32 for DirectX 10, 37 for DirectX 11, 27 for DirectX 12, 87 for DirectX 9, 899 for G2D, 5983 for G3D, and 2557 for GPU compute. The average benchmark score is 6078.

The RTX A400 sits at the 35th percentile of all GPUs with a 0.5% delta above the NVIDIA Quadro P2000 (6049) and a 1% delta above the AMD Radeon 760M (6019). It trails the Intel Iris Pro Graphics 6200 (6117) by 0.6%. The NVIDIA GeForce MX230 scores 6077, essentially tied.

The MI355X has no benchmark entries and sits at the 50th percentile with an average benchmark score of 0. This absence of recorded data means its performance standing is based entirely on architectural specifications.

Clock behavior differs: the RTX A400 has a higher base clock (1417 MHz versus 1000 MHz) but a lower boost clock (1762 MHz versus 2400 MHz). The MI355X’s boost clock is 36% higher than its base, while the RTX A400’s boost is 24% above its base.

Power efficiency is not directly comparable, but the TDP figures show the MI355X consumes 28 times the power of the RTX A400 (1400 W versus 50 W). The MI355X’s FP32 per watt is approximately 0.056 TFLOPS/W, while the RTX A400 achieves approximately 0.054 TFLOPS/W, a near tie.

The RTX A400 supports modern graphics APIs including DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4, enabling workstation visualization workloads. The MI355X lists no API support, confirming its role as a compute accelerator without graphics rendering capabilities.