AMD Instinct MI455X vs NVIDIA L20 Comparison

FAQ

Q: What are the core specifications of the AMD Instinct MI455X and NVIDIA L20?

A: The AMD Instinct MI455X uses the MI450 256CU chip built on a 2 nm process with 320,000 million transistors on a 2990 mm² die. It features 32,768 shading units, 1,024 TMUs, and 432 GB of HBM4 memory on a 24,576-bit bus with 23.3 TB/s bandwidth. The NVIDIA L20 uses the AD102 chip on a 5 nm process with 76,300 million transistors on a 609 mm² die. It has 11,776 shading units, 368 TMUs, 128 ROPs, 92 RT cores, and 368 tensor cores, with 48 GB of GDDR6 memory on a 384-bit bus delivering 864.0 GB/s.

Q: What are the clock speeds and power requirements for each card?

A: The AMD Instinct MI455X has a base clock of 1000 MHz and a boost clock of 2400 MHz, with a TDP of 2300 W and a suggested PSU of 2700 W. The NVIDIA L20 has a base clock of 1440 MHz and a boost clock of 2520 MHz, with a TDP of 275 W and a suggested PSU of 600 W.

Q: What is the memory configuration difference between the two?

A: The AMD Instinct MI455X uses HBM4 memory totaling 432 GB with a 24,576-bit bus and 23.3 TB/s bandwidth. The NVIDIA L20 uses GDDR6 memory totaling 48 GB with a 384-bit bus and 864.0 GB/s bandwidth. The MI455X offers roughly 27 times the memory capacity and over 26 times the bandwidth of the L20.

Q: What are the physical and interface differences?

A: The AMD Instinct MI455X is an EAM Module with no display outputs and a PCIe 6.0 x16 interface. The NVIDIA L20 is a dual-slot card measuring 267 mm in length and 111 mm in height, with 4x DisplayPort 1.4a outputs and a PCIe 4.0 x16 interface. The L20 uses a 1x 16-pin power connector, while the MI455X has no power connectors listed.

Q: What benchmark data exists for these cards in the database?

A: The NVIDIA L20 has recorded scores of 274,276 in Geekbench OpenCL and 228,018 in Geekbench Vulkan, giving it an average benchmark score of 251,147. The AMD Instinct MI455X has no recorded benchmark scores in the database, and its average benchmark score is listed as 0.

Q: How do the cards compare in percentile ranking?

A: The NVIDIA L20 ranks in the 99th percentile among all GPUs in the database. The AMD Instinct MI455X ranks in the 50th percentile, though this is based on no recorded benchmark scores, so the percentile reflects the absence of data rather than measured performance.

The Verdict

The database contains no head-to-head benchmark results between the AMD Instinct MI455X and the NVIDIA L20. The MI455X has zero recorded benchmark scores, while the L20 has two recorded scores with a 99th percentile ranking. This means any direct performance comparison relies entirely on the specification data available.

For compute-intensive workloads requiring massive memory capacity and bandwidth, the AMD Instinct MI455X presents a specification profile built around extreme scale. Its 432 GB of HBM4 memory and 23.3 TB/s bandwidth are unmatched by the L20's 48 GB and 864.0 GB/s. The MI455X also delivers 157.3 TFLOPS of FP32 and FP16 compute, compared to 59.35 TFLOPS for the L20 in both precision formats.

For deployment in existing server infrastructure with power constraints, the NVIDIA L20 offers a dramatically lower power profile at 275 W versus 2300 W for the MI455X. The L20 also provides display outputs, API support for DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4, while the MI455X has no display outputs and no supported graphics APIs.

The L20 has an active production status and a release date of November 2023. The MI455X has a release date of July 2026 and no production status listed. The L20's predecessor is Server Ampere, and its successor is Server Hopper. The MI455X's predecessor is Radeon Instinct, with no successor listed.

The data suggests two divergent design goals. The MI455X prioritizes raw compute scale, memory capacity, and bandwidth for large-scale data processing. The L20 prioritizes efficiency, compatibility, and versatility in a standard dual-slot form factor. Users with power budgets and existing PCIe 4.0 infrastructure would find the L20 more practical. Users requiring the largest possible memory footprint and compute throughput would need to accommodate the MI455X's EAM Module form factor and 2700 W PSU requirement.

Head-to-Head Benchmarks

No head-to-head benchmark results exist in the database for these two cards. The wins count shows 0 for both the AMD Instinct MI455X and the NVIDIA L20. This absence of comparative data means the analysis must proceed through specification differences and the L20's standalone benchmark scores.

The NVIDIA L20's Geekbench OpenCL score of 274,276 places it ahead of the NVIDIA PG506-232 by 11.6%, whose average score is 225,124. The L20 also leads the AMD Radeon PRO W7900D by 14.2%, which scores 219,827. However, the L20 trails the NVIDIA L40 by 11.6%, which scores 284,111, and the NVIDIA RTX 6000 Ada Generation by 12.6%, which scores 287,237.

These nearest rival comparisons give context to the L20's performance tier. The L20 sits between the PG506-232 and the L40 in average benchmark score, closer to the higher-end cards than to the lower ones. The 11.6% gap to the L40 and 12.6% gap to the RTX 6000 Ada Generation indicate the L20 is a capable server compute card, though not the top performer in its class.

The Geekbench Vulkan score for the L20 is 228,018, which is lower than its OpenCL score of 274,276. This difference of 46,258 points suggests the L20 performs better in OpenCL workloads than in Vulkan workloads, which aligns with its server compute orientation.

For the AMD Instinct MI455X, there are no benchmark scores to compare. The database lists its average benchmark score as 0, and its percentile ranking of 50 reflects the absence of measured data rather than a performance estimate. Without recorded scores, the MI455X cannot be positioned relative to any rivals in the database.

The specification data shows the MI455X offers 157.3 TFLOPS in both FP32 and FP16, which is 2.65 times the L20's 59.35 TFLOPS in both precisions. The texture rate for the MI455X is 2,457.6 GTexel/s, compared to 927.4 GTexel/s for the L20, a 2.65 times difference. The L20 has a pixel rate of 322.6 GPixel/s, while the MI455X has a pixel rate of 0 MPixel/s, indicating the MI455X is not designed for rasterization output.

Specification Differences

The most striking difference is memory capacity. The AMD Instinct MI455X uses 432 GB of HBM4, while the NVIDIA L20 uses 48 GB of GDDR6. This is a 9 times difference in capacity. The memory bus width differs significantly: 24,576 bits for the MI455X versus 384 bits for the L20. Memory bandwidth follows proportionally, with 23.3 TB/s for the MI455X and 864.0 GB/s for the L20.

The compute units differ substantially. The MI455X has 32,768 shading units and 1,024 TMUs, with 0 ROPs. The L20 has 11,776 shading units, 368 TMUs, and 128 ROPs. The MI455X has no RT cores or tensor cores listed, while the L20 has 92 RT cores and 368 tensor cores.

Process technology differs by node: the MI455X is on 2 nm, while the L20 is on 5 nm. Both use TSMC as the foundry. Transistor counts are 320,000 million for the MI455X and 76,300 million for the L20. Die size is 2990 mm² for the MI455X and 609 mm² for the L20. The transistor density is 107.0M per mm² for the MI455X and 125.3M per mm² for the L20, meaning the L20 packs transistors more densely despite using a larger node.

Clock speeds favor the L20. The L20 has a base clock of 1440 MHz and a boost clock of 2520 MHz. The MI455X has a base clock of 1000 MHz and a boost clock of 2400 MHz. The memory clock for the MI455X is 1900 MHz (7.6 Gbps effective), while the L20 runs at 2250 MHz (18 Gbps effective).

Power specifications are drastically different. The MI455X has a TDP of 2300 W and requires a 2700 W PSU. The L20 has a TDP of 275 W and requires a 600 W PSU. The MI455X uses an EAM Module slot width with no power connectors, while the L20 is dual-slot with a 1x 16-pin connector.

Bus interfaces differ: the MI455X uses PCIe 6.0 x16, while the L20 uses PCIe 4.0 x16. Display outputs are absent on the MI455X, while the L20 has 4x DisplayPort 1.4a. The L20 has dimensions of 267 mm length and 111 mm height; the MI455X has no listed dimensions.

Architecture Differences

The AMD Instinct MI455X uses the CDNA 5.0 architecture, designed specifically for compute acceleration. The NVIDIA L20 uses the Ada Lovelace architecture, which includes both compute and graphics capabilities. This architectural split explains the presence of RT cores and tensor cores on the L20 and their absence on the MI455X.

The MI455X's CDNA 5.0 architecture targets data center compute without any display or graphics API support. Its API list shows N/A for DirectX, OpenGL, and Vulkan. The L20's Ada Lovelace architecture supports DirectX 12 Ultimate (12_2), OpenGL 4.6, and Vulkan 1.4, making it usable in graphics workloads as well as compute.

The memory architectures differ fundamentally. The MI455X uses HBM4, a high-bandwidth stacked memory design that enables its 23.3 TB/s bandwidth. The L20 uses GDDR6, a more conventional memory type with lower bandwidth per bit but lower cost and power. The MI455X's 24,576-bit bus is 64 times wider than the L20's 384-bit bus, which is the primary driver of its bandwidth advantage.

The MI455X has no pixel rate, indicating it lacks the rasterization pipeline present in the L20. The L20's 322.6 GPixel/s pixel rate confirms its graphics capability. The MI455X's texture rate of 2,457.6 GTexel/s exceeds the L20's 927.4 GTexel/s, reflecting its higher TMU count and compute focus.

The transistor density difference provides insight into design priorities. The L20 achieves 125.3M transistors per mm² on a 609 mm² die, while the MI455X achieves 107.0M per mm² on a 2990 mm² die. The MI455X's larger die allows for more total transistors but lower density, suggesting a design optimized for memory controllers and compute units rather than compact integration.

The release dates differ by roughly two and a half years. The NVIDIA L20 was released in November 2023, while the AMD Instinct MI455X is dated July 2026. The L20's production status is listed as Active, while the MI455X has no production status. The L20's predecessor is Server Ampere, and its successor is Server Hopper. The MI455X's predecessor is Radeon Instinct.

The power architecture reveals the scale difference. The MI455X requires a 2700 W PSU and has no power connectors, consistent with an EAM Module that receives power through its mounting interface. The L20 requires a 600 W PSU and uses a standard 1x 16-pin connector. This 4.5 times difference in system power requirement is a major deployment consideration.

Where Each One Wins

The AMD Instinct MI455X wins in scenarios requiring extreme memory capacity. Its 432 GB of HBM4 memory dwarfs the L20's 48 GB, making it suitable for workloads that need to hold massive datasets in memory without host-side transfers. The 23.3 TB/s bandwidth supports data movement at a scale the L20 cannot approach.

The MI455X also wins in raw compute throughput. Its 157.3 TFLOPS in FP32 and FP16 is 2.65 times the L20's 59.35 TFLOPS in both precisions. The MI455X's 2,457.6 GTexel/s texture rate exceeds the L20's 927.4 GTexel/s by the same factor. For pure compute workloads that fit within the memory constraints, the MI455X delivers significantly more processing capability.

The MI455X uses PCIe 6.0 x16, which provides a newer bus interface than the L20's PCIe 4.0 x16. This newer interface enables higher host-to-device transfer speeds, benefiting workloads that stream data from the CPU.

The NVIDIA L20 wins in power efficiency. Its 275 W TDP versus the MI455X's 2300 W TDP means the L20 delivers its 59.35 TFLOPS at roughly one-twelfth the power draw per card. For deployments with power limits, the L20 allows multiple cards in the space of one MI455X's power budget.

The L20 wins in compatibility and versatility. It supports DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4, making it usable for graphics workloads. The MI455X has no API support listed. The L20 also provides 4x DisplayPort 1.4a outputs, while the MI455X has none.

The L20 wins in physical form factor. Its dual-slot design with 267 mm length and 111 mm height fits standard server chassis. The MI455X uses an EAM Module form factor, which requires specialized mounting and infrastructure. The L20's 1x 16-pin power connector is standard, while the MI455X relies on its module interface for power.

The L20 wins in production readiness. Its production status is Active, and it has recorded benchmark scores in the database. The MI455X has no production status and no benchmark scores, making its real-world performance unverified in the database.

The L20 also wins in the nearest rival comparison. Its average benchmark score of 251,147 places it 11.6% above the NVIDIA PG506-232 and 14.2% above the AMD Radeon PRO W7900D. While it trails the L40 and RTX 6000 Ada Generation, the L20 occupies a solid mid-to-high position in the server compute tier. The MI455X has no rival comparisons available.

For memory bandwidth per watt, the L20 delivers 864.0 GB/s at 275 W, which is 3.14 GB/s per watt. The MI455X delivers 23.3 TB/s at 2300 W, which is 10.13 GB/s per watt. The MI455X is more bandwidth-efficient per watt, but its absolute power requirement is prohibitive in many environments.

For compute per watt, the L20 delivers 59.35 TFLOPS at 275 W, which is 0.216 TFLOPS per watt. The MI455X delivers 157.3 TFLOPS at 2300 W, which is 0.068 TFLOPS per watt. The L20 is over three times more compute-efficient per watt.

The choice between these cards depends on whether the workload demands the MI455X's massive memory and compute scale or the L20's efficiency and compatibility. The data does not support a universal winner, only distinct use-case advantages.