AMD Instinct MI455X vs NVIDIA RTX PRO 4000 Blackwell Comparison

The Verdict

The database comparison between the AMD Instinct MI455X and the NVIDIA RTX PRO 4000 Blackwell presents a fundamental divide in purpose and capability. The AMD Instinct MI455X is a compute-oriented accelerator with a 50th percentile ranking among all GPUs, while the NVIDIA RTX PRO 4000 Blackwell sits at the 72nd percentile. The NVIDIA card has a full suite of benchmark scores, averaging 27,135 points, whereas the AMD part has no recorded benchmarks and an average score of zero. This means the RTX PRO 4000 Blackwell delivers measurable, verified graphics and compute performance, while the MI455X's actual workload behavior remains unquantified in the database.

The RTX PRO 4000 Blackwell is the only part with usable data for standard workstation tasks. Its scores in DirectX 12, Vulkan, and compute tests are all recorded, with the highest being a Geekbench Vulkan score of 194,168 and a Passmark G3D score of 28,427. The MI455X, with its 432 GB of HBM4 memory and 23.3 TB/s bandwidth, is clearly built for massive memory-bound workloads, but without benchmark data, its real-world performance cannot be compared directly. The verdict from the data: choose the NVIDIA RTX PRO 4000 Blackwell for any task requiring verified graphics, ray tracing, or general compute performance. Choose the AMD Instinct MI455X only if the requirement is extreme memory capacity and bandwidth, accepting that no benchmark scores exist to validate its performance.

Architecture Differences

The two accelerators use entirely different architectures and manufacturing approaches. The AMD Instinct MI455X uses the CDNA 5.0 architecture on a 2 nm process from TSMC, with a chip labeled MI450 256CU. The NVIDIA RTX PRO 4000 Blackwell uses the Blackwell 2.0 architecture on a 5 nm process, also from TSMC, with the GB203 chip. The process node difference is substantial: 2 nm versus 5 nm, which directly impacts transistor density and power characteristics.

Transistor counts differ dramatically. The MI455X packs 320,000 million transistors on a die size of 2990 mm², yielding a density of 107.0 million transistors per square millimeter. The RTX PRO 4000 Blackwell has 45,600 million transistors on a 378 mm² die, with a higher density of 120.6 million per square millimeter. Despite the larger node, the NVIDIA chip achieves higher transistor density due to its much smaller die and different design priorities.

The MI455X has 32,768 shading units and 1,024 texture mapping units, but zero ROPs and no pixel rate. This confirms its role as a pure compute accelerator with no rasterization pipeline. The RTX PRO 4000 Blackwell has 8,960 shading units, 280 TMUs, 96 ROPs, 70 ray tracing cores, and 280 tensor cores, with a pixel rate of 197.3 GPixel/s. The NVIDIA part is a full graphics processor with ray tracing and tensor acceleration, while the AMD part is stripped of display and rasterization hardware entirely.

Memory architecture is another major divergence. The MI455X uses 432 GB of HBM4 with a 24,576-bit bus and 23.3 TB/s bandwidth. The RTX PRO 4000 Blackwell uses 24 GB of GDDR7 with a 192-bit bus and 672.0 GB/s bandwidth. The AMD card has 18 times the memory capacity and roughly 35 times the bandwidth, but the NVIDIA card uses a simpler, more power-efficient memory subsystem.

Head-to-Head Benchmarks

Because the AMD Instinct MI455X has no recorded benchmark scores, the head-to-head comparison is entirely one-sided. The NVIDIA RTX PRO 4000 Blackwell has nine benchmark entries in the database, and the AMD part has zero. This absence of data is itself a significant finding: the MI455X cannot be evaluated for standard graphics or compute workloads using the database's measurement suite.

The RTX PRO 4000 Blackwell's benchmark results show a strong, balanced profile. In 3DMark Steel Nomad DX12, it scores 4,648. Its Geekbench Vulkan result is 194,168, which is the highest single score in its record. Passmark tests show varied results: DirectX 9 scores 354, DirectX 10 scores 173, DirectX 11 scores 276, and DirectX 12 scores 97. The G2D score is 1,265, while the G3D score is 28,427. The GPU compute score is 14,805.

The nearest rivals for the RTX PRO 4000 Blackwell provide context for its performance. The AMD Radeon RX 6700 XT has an average score of 27,425, which is 1.1% higher than the RTX PRO 4000 Blackwell's average of 27,135. The NVIDIA GeForce RTX 4070 Mobile also scores 27,435, also 1.1% higher. The NVIDIA GeForce RTX 3090 scores 27,565, which is 1.6% higher. The NVIDIA RTX A4000 scores 26,683, which is 1.7% lower. This places the RTX PRO 4000 Blackwell in a tight cluster of comparable GPUs, all within roughly 2% of each other in average benchmark score.

The MI455X's lack of data means it cannot be placed in this competitive context. Its 50th percentile ranking versus all GPUs, combined with zero benchmark scores, suggests the database has not yet measured its performance. The RTX PRO 4000 Blackwell's 72nd percentile ranking, by contrast, is backed by a full set of measurements.

Specification Differences

The specification sheets for the two parts differ in nearly every field. The AMD Instinct MI455X uses a 2 nm process, while the NVIDIA RTX PRO 4000 Blackwell uses 5 nm. Transistor counts are 320,000 million versus 45,600 million, and die sizes are 2990 mm² versus 378 mm². The MI455X has a higher transistor density in absolute terms, but the NVIDIA part has a higher density per square millimeter.

Clock speeds differ in both base and boost. The MI455X runs at 1000 MHz base and 2400 MHz boost, while the RTX PRO 4000 Blackwell runs at 1230 MHz base and 2055 MHz boost. The memory clocks also differ: the MI455X uses 1900 MHz with 7.6 Gbps effective, while the NVIDIA part uses 1750 MHz with 28 Gbps effective. Memory capacity and type are completely different: 432 GB HBM4 versus 24 GB GDDR7, with bus widths of 24,576 bits versus 192 bits, and bandwidths of 23.3 TB/s versus 672.0 GB/s.

Compute capabilities show the MI455X's raw throughput advantage. Its FP32 performance is 157.3 TFLOPS, and FP16 is also 157.3 TFLOPS at a 1:1 ratio. The RTX PRO 4000 Blackwell delivers 36.83 TFLOPS for both FP32 and FP16, also at 1:1. The AMD part has 4.27 times the FP32 throughput, but this comes at a massive power cost. The TDP is 2300 W for the MI455X versus 140 W for the RTX PRO 4000 Blackwell. The suggested PSU is 2700 W versus 300 W.

Form factor and connectivity also diverge. The MI455X is an EAM Module with no power connectors and no display outputs, using PCIe 6.0 x16. The RTX PRO 4000 Blackwell is a single-slot card with a 1x 16-pin power connector, 4x DisplayPort 2.1b outputs, and PCIe 5.0 x16. The NVIDIA part measures 241 mm in length, 111 mm in height, and 20 mm in width. The AMD part has no recorded dimensions.

API support is another clear differentiator. The MI455X has no DirectX, OpenGL, or Vulkan support, listed as N/A for all three. The RTX PRO 4000 Blackwell supports DirectX 12 Ultimate (12_2), OpenGL 4.6, and Vulkan 1.4. Release dates also differ: the MI455X was released on 2026-07-22, while the RTX PRO 4000 Blackwell was released on 2025-03-17. The NVIDIA part's production status is Active, while the AMD part has no recorded production status.

FAQ

Q: Which GPU has higher benchmark scores in the database?

A: The NVIDIA RTX PRO 4000 Blackwell has all recorded benchmark scores, with an average of 27,135 and a 72nd percentile ranking. The AMD Instinct MI455X has no benchmark scores and an average of zero, placing it at the 50th percentile.

Q: How does the RTX PRO 4000 Blackwell compare to its nearest rivals?

A: The RTX PRO 4000 Blackwell's average score of 27,135 is 1.1% lower than the AMD Radeon RX 6700 XT and the NVIDIA GeForce RTX 4070 Mobile, 1.6% lower than the NVIDIA GeForce RTX 3090, and 1.7% higher than the NVIDIA RTX A4000.

Q: What is the memory capacity difference between the two parts?

A: The AMD Instinct MI455X has 432 GB of HBM4 memory with a 24,576-bit bus and 23.3 TB/s bandwidth. The NVIDIA RTX PRO 4000 Blackwell has 24 GB of GDDR7 memory with a 192-bit bus and 672.0 GB/s bandwidth.

Q: Does the AMD Instinct MI455X support graphics APIs?

A: No. The database lists DirectX, OpenGL, and Vulkan support as N/A for the MI455X. The RTX PRO 4000 Blackwell supports DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4.

Q: What is the power requirement for each card?

A: The AMD Instinct MI455X has a TDP of 2300 W and a suggested PSU of 2700 W. The NVIDIA RTX PRO 4000 Blackwell has a TDP of 140 W and a suggested PSU of 300 W.

Q: Which card has ray tracing and tensor cores?

A: Only the NVIDIA RTX PRO 4000 Blackwell, with 70 ray tracing cores and 280 tensor cores. The AMD Instinct MI455X does not list any ray tracing or tensor core counts.

Q: What are the release dates for the two products?

A: The AMD Instinct MI455X was released on 2026-07-22, and the NVIDIA RTX PRO 4000 Blackwell was released on 2025-03-17. The NVIDIA part has an Active production status, while the AMD part has no recorded status.