AMD Instinct MI300X vs AMD Instinct MI455X Comparison

FAQ

Q: What is the performance difference between the MI300X and the MI455X?

A: The database shows the MI300X has a Geekbench OpenCL score of 317994, while the MI455X has no recorded benchmark scores. The MI455X shows an average benchmark score of 0, so direct measured performance comparison is not possible from the recorded data.

Q: How do the memory specifications differ?

A: The MI300X uses 192 GB of HBM3 memory with an 8192-bit bus and 5.32 TB/s bandwidth. The MI455X uses 432 GB of HBM4 memory with a 24576-bit bus and 23.3 TB/s bandwidth, nearly 4.4 times the bandwidth of the older part.

Q: Which card has more compute units?

A: The MI455X has 32768 shading units, compared to 19456 on the MI300X. This is a 68% increase in shading units.

Q: What are the clock speeds?

A: Both have a 1000 MHz base clock. The MI300X boosts to 2100 MHz while the MI455X boosts to 2400 MHz. The MI455X also runs its memory at 1900 MHz (7.6 Gbps effective) versus 1300 MHz (5.2 Gbps effective) on the MI300X.

Q: What is the transistor count and process node?

A: The MI300X uses 153,000 million transistors on a 5 nm TSMC process. The MI455X uses 320,000 million transistors on a 2 nm TSMC process. The MI455X has more than double the transistor count.

Q: What power delivery is required?

A: The MI300X has a TDP of 750 W and a suggested PSU of 1150 W. The MI455X has a TDP of 2300 W and a suggested PSU of 2700 W.

Where Each One Wins

The MI300X wins in the only measurable benchmark category. Its Geekbench OpenCL score of 317994 places it at the 100th percentile of all GPUs in the database. The MI455X, by contrast, has no recorded benchmark results, which means there is no empirical evidence of a win in any measured workload from the database.

For practical use cases, the MI455X wins on paper specifications that matter for large-scale compute. It has 432 GB of memory versus 192 GB, 23.3 TB/s of bandwidth versus 5.32 TB/s, 32768 shading units versus 19456, and 157.3 TFLOPS FP32 versus 81.72 TFLOPS. These are theoretical maxima, not measured results.

The MI300X wins on power efficiency per the recorded data. It delivers 81.72 TFLOPS at 750 W, while the MI455X delivers 157.3 TFLOPS at 2300 W. The MI300X produces 0.109 TFLOPS per watt versus 0.068 TFLOPS per watt for the MI455X.

The MI300X also wins on existing deployment evidence. The database records it at the 100th percentile with a real score, while the MI455X sits at the 50th percentile with a zero score, indicating a lack of validated results.

Architecture Differences

The MI300X uses the CDNA 3.0 architecture with the Aqua Vanjaram chip. The MI455X uses the CDNA 5.0 architecture with the MI450 256CU chip. This is a two-generation architectural jump.

The fabrication process differs significantly. The MI300X is built on a 5 nm TSMC node with 153,000 million transistors on a 1017 mm² die. The MI455X is built on a 2 nm TSMC node with 320,000 million transistors on a 2990 mm² die. The MI455X die is nearly three times larger in area and holds more than double the transistors. Transistor density is actually lower on the MI455X: 107.0M per mm² versus 150.4M per mm² on the MI300X, which reflects the larger die scaling.

Memory architecture is a major divergence. The MI300X uses HBM3 with a 8192-bit bus. The MI455X uses HBM4 with a 24576-bit bus, triple the bus width. Memory bandwidth jumps from 5.32 TB/s to 23.3 TB/s.

The MI455X has 32768 shading units and 1024 TMUs. The MI300X has 19456 shading units and 1216 TMUs. The MI455X has more shaders but fewer texture units. Both parts have zero ROPs and no display outputs, consistent with accelerator-class hardware.

Both parts have no DirectX, OpenGL, or Vulkan API support, as recorded in the database. Neither has RT cores or tensor cores listed.

The MI455X uses an EAM Module slot width while the MI300X uses an OAM Module. Neither has power connectors, as both are designed for module-based integration.

The bus interface differs: the MI300X uses PCIe 5.0 x16 while the MI455X uses PCIe 6.0 x16.

Specification Differences

The MI455X doubles the memory capacity: 432 GB versus 192 GB.

Memory type changes from HBM3 to HBM4.

Memory bus width triples: 24576 bit versus 8192 bit.

Memory bandwidth increases from 5.32 TB/s to 23.3 TB/s, a 4.38 times increase.

Shading units increase from 19456 to 32768, a 68.4% increase.

TMUs decrease from 1216 to 1024, a 15.8% decrease.

Boost clock rises from 2100 MHz to 2400 MHz, a 14.3% increase. Base clocks are identical at 1000 MHz.

Memory clock rises from 1300 MHz to 1900 MHz, a 46.2% increase.

FP32 compute rises from 81.72 TFLOPS to 157.3 TFLOPS, a 92.5% increase. FP16 is listed at the same rates with 1:1 ratio on both parts.

Texture rate decreases from 2,553.6 GTexel/s to 2,457.6 GTexel/s, a 3.8% decrease, consistent with the lower TMU count.

TDP rises from 750 W to 2300 W, a 206.7% increase.

Suggested PSU rises from 1150 W to 2700 W.

Transistor count rises from 153,000 million to 320,000 million, a 109.2% increase.

Die size rises from 1017 mm² to 2990 mm², a 194% increase.

Process node changes from 5 nm to 2 nm.

Slot width changes from OAM Module to EAM Module.

Bus interface changes from PCIe 5.0 x16 to PCIe 6.0 x16.

Head-to-Head Benchmarks

The database has no head-to-head benchmark entries for these two parts. The MI300X has a single recorded Geekbench OpenCL score of 317994, while the MI455X has no recorded scores.

Looking at the MI300X's nearest rivals provides context for its measured performance. It sits 5% behind the NVIDIA H200 NVL which scores 334891, 8% behind the NVIDIA B200 which scores 345482, 7.5% ahead of the NVIDIA L40S which scores 295763, and 10.7% ahead of the NVIDIA RTX 6000 Ada Generation which scores 287237.

The MI455X has no nearest rivals listed and no benchmark data. Its theoretical FP32 output of 157.3 TFLOPS is 92.5% higher than the MI300X's 81.72 TFLOPS, but this is a computed specification, not a measured result.

The MI455X's 23.3 TB/s memory bandwidth is a 4.38 times improvement over the MI300X's 5.32 TB/s. Its 432 GB capacity is 2.25 times the MI300X's 192 GB.

The MI455X's boost clock of 2400 MHz is 14.3% higher than the MI300X's 2100 MHz. Its memory clock of 1900 MHz is 46.2% higher.

The MI455X has 68.4% more shading units but 15.8% fewer TMUs. The texture rate difference is small: 2,457.6 GTexel/s versus 2,553.6 GTexel/s, a 3.8% deficit for the MI455X.

Power scaling is unfavorable for the MI455X. It consumes 206.7% more power for 92.5% more FP32 throughput. The MI300X maintains a higher compute-per-watt ratio based on the recorded specifications.

The Verdict

The MI300X is the only one of the two with validated performance data. Its Geekbench OpenCL score of 317994 places it at the 100th percentile of all GPUs in the database, and it beats the NVIDIA L40S by 7.5% and the RTX 6000 Ada Generation by 10.7%. It trails the NVIDIA H200 NVL by 5% and the B200 by 8%.

The MI455X is a specification sheet with no measured results. Its 157.3 TFLOPS FP32, 432 GB HBM4 memory, 23.3 TB/s bandwidth, and 32768 shading units are all theoretical maxima. The 50th percentile ranking and zero average benchmark score reflect the absence of recorded data, not a measured performance level.

For a buyer who needs a proven accelerator today, the MI300X is the defensible choice. It has a recorded score, a 100th percentile ranking, and a known competitive position against NVIDIA's current accelerators. Its 750 W TDP and 1150 W suggested PSU are within the range of existing server infrastructure.

For a buyer planning around the MI455X's specifications, the data supports expectations of substantial raw compute and memory advantages. The 23.3 TB/s bandwidth and 432 GB capacity are transformative on paper. The 2400 MHz boost clock and 32768 shading units suggest significant throughput potential. However, the 2300 W TDP and 2700 W suggested PSU demand a power delivery system far beyond what the MI300X requires.

The MI455X's lower transistor density of 107.0M per mm² versus 150.4M per mm² indicates the 2 nm node is being used for a massive die rather than a compact one. The 2990 mm² die size is a physical constraint that will affect packaging and cooling design.

The MI300X wins the measured performance comparison because there is no measurement for the MI455X. The MI455X wins the specification comparison across nearly every compute and memory metric. The absence of head-to-head benchmarks means the actual performance gap between these two parts remains unquantified in the database.

The MI300X is the pick for validated, deployable compute with known competitive standing. The MI455X is the pick for maximum theoretical capability, provided the 2300 W power envelope and EAM Module form factor fit the target system. The 92.5% FP32 advantage and 4.38 times memory bandwidth advantage are substantial on paper, but they carry a 206.7% power increase that cannot be ignored in system design.