AMD Instinct MI300X vs NVIDIA B300 SXM6 AC Comparison

The NVIDIA B300 SXM6 AC and AMD Instinct MI300X represent two distinct approaches to high-density acceleration, and the benchmark data provides a clear, if narrow, point of comparison. In the single available benchmark test, Geekbench OpenCL, the NVIDIA B300 SXM6 AC posts a score of 369,831, while the AMD Instinct MI300X achieves 317,994. This yields a 16.3% advantage for the NVIDIA part, a substantial margin that establishes it as the faster of the two in this specific compute workload. The data shows a definitive winner, though the broader context of their respective rival sets reveals a more nuanced competitive landscape.

Head-to-Head Benchmarks

The head-to-head comparison is straightforward: the NVIDIA B300 SXM6 AC wins the only benchmark test recorded, the Geekbench OpenCL, with a delta of 16.3% over the AMD Instinct MI300X. This is a significant performance gap, placing the B300 in a class of its own relative to the MI300X. To contextualize this margin, consider the performance relationships each card has with common rivals. The B300’s nearest rival, the NVIDIA B200, scores 345,482, which is 7% lower. This means the B300’s lead over the MI300X is more than double its lead over its direct predecessor, highlighting a generational leap that the AMD card cannot match.

The MI300X is not without its own competitive standing. While it trails the B300 by 16.3%, the data shows it holds a 7.5% advantage over the NVIDIA L40S, which scores 295,763. It also outperforms the NVIDIA RTX 6000 Ada Generation, which scores 287,237, by 10.7%. This suggests the MI300X is a formidable performer in absolute terms, but the gap to the B300 is the defining metric in this matchup. The B300’s 16.3% lead is not merely a marginal victory; it is a decisive performance tier separation. For workloads where OpenCL performance is a proxy for general compute throughput, the B300 is the clear choice based on this data alone.

Interestingly, the rival comparisons also show how each card positions against the NVIDIA H200 NVL. The B300 is 10.4% ahead of the H200 NVL (which scores 334,891), while the MI300X is 5% behind the same card. This triangulation reinforces the hierarchy: the B300 leads the pack, the H200 NVL and MI300X occupy a similar mid-tier, and the L40S trails. The delta between the B300 and MI300X (16.3%) is larger than the delta between the MI300X and the H200 NVL (5%), indicating that the AMD card is much closer to the previous-generation NVIDIA flagship than it is to the current one.

FAQ

Q: Which GPU has the higher Geekbench OpenCL score?

A: The NVIDIA B300 SXM6 AC scores 369,831, which is 16.3% higher than the AMD Instinct MI300X’s score of 317,994.

Q: How does the AMD Instinct MI300X compare to the NVIDIA B200?

A: The MI300X scores 317,994, which is 8% lower than the NVIDIA B200’s score of 345,482.

Q: What is the performance relationship between the AMD Instinct MI300X and the NVIDIA L40S?

A: The MI300X is 7.5% ahead of the NVIDIA L40S, which has an average score of 295,763.

Q: Is the NVIDIA B300 SXM6 AC the fastest GPU in its immediate rival group?

A: Yes, the B300’s score of 369,831 is higher than all its nearest rivals, including the B200 (345,482), H200 NVL (334,891), MI300X (317,994), and L40S (295,763).

Q: Which card has a larger performance lead over the NVIDIA H200 NVL?

A: The NVIDIA B300 SXM6 AC is 10.4% ahead of the H200 NVL, while the AMD Instinct MI300X is 5% behind it.

Q: What does the deltaPct of 16.3% signify in the head-to-head?

A: It signifies that the NVIDIA B300 SXM6 AC outperforms the AMD Instinct MI300X by 16.3% in the Geekbench OpenCL test, representing the only recorded benchmark win in this comparison.

Architecture Differences

The architectural philosophies of the two cards diverge sharply, starting with the silicon itself. The NVIDIA B300 is built on the Blackwell Ultra architecture, using the GB110 chip manufactured on a 5 nm process by TSMC. The AMD MI300X uses the CDNA 3.0 architecture with the Aqua Vanjaram chip, also on a 5 nm TSMC process. Both are large dies, but the B300’s is notably bigger: 1628 mm² compared to the MI300X’s 1017 mm². This size difference is reflected in transistor count, where the B300 packs 208,000 million transistors versus the MI300X’s 153,000 million. However, the MI300X achieves a higher transistor density of 150.4M / mm², compared to the B300’s 127.8M / mm², indicating a more tightly packed design on a smaller die.

Memory subsystems also differ significantly. The B300 features 288 GB of HBM3e memory with a bandwidth of 8.19 TB/s, while the MI300X offers 192 GB of HBM3 with a bandwidth of 5.32 TB/s. Both utilize an 8192-bit bus width, but the B300’s faster memory type and higher effective speed (2000 MHz, 8 Gbps effective) give it a substantial bandwidth advantage over the MI300X’s 1300 MHz, 5.2 Gbps effective. In terms of compute resources, the MI300X has more shading units (19,456 vs. 18,944) and more texture mapping units (1,216 vs. 592), leading to a higher texture rate of 2,553.6 GTexel/s versus the B300’s 1,202.9 GTexel/s. Conversely, the B300 has dedicated tensor cores (592 of them), while the MI300X does not list any, relying instead on its raw FP32/FP16 compute. In raw floating-point throughput, the MI300X edges out the B300: 81.72 TFLOPS for FP32 and FP16 versus the B300’s 76.99 TFLOPS for both. The B300 also has a minimal pixel rate of 48.77 GPixel/s with 24 ROPs, while the MI300X reports 0 MPixel/s and 0 ROPs, reflecting its compute-focused design.

Power and interface specs further separate the two. The B300 is a 1100 W SXM Module with a suggested PSU of 1500 W, while the MI300X is a 750 W OAM Module with a suggested PSU of 1150 W. The B300 uses a PCIe 6.0 x16 interface, whereas the MI300X uses PCIe 5.0 x16. Neither card has display outputs, and both list N/A for DirectX, OpenGL, and Vulkan APIs, indicating they are purely accelerators for headless compute environments.

The Verdict

Based strictly on the benchmark data, the NVIDIA B300 SXM6 AC is the superior performer in this comparison. Its 16.3% lead in Geekbench OpenCL, combined with its higher average benchmark score (369,831 vs. 317,994), makes it the definitive choice for workloads where that specific compute metric is the primary consideration. The data shows the B300 not only beats the MI300X but also outpaces every other rival in its list, including the B200, H200 NVL, and L40S. For users prioritizing peak raw performance in a single accelerators, the B300 is the clear winner.

However, the AMD Instinct MI300X is not a poor performer; it holds a 7.5% lead over the L40S and a 10.7% lead over the RTX 6000 Ada Generation. Its advantages in FP32/FP16 throughput (81.72 TFLOPS) and texture rate (2,553.6 GTexel/s) suggest it may excel in specific compute patterns not captured by the single OpenCL test. Furthermore, its lower power draw (750 W vs. 1100 W) and lower suggested PSU (1150 W vs. 1500 W) indicate a more power-efficient design per unit of compute, though the data does not provide a direct performance-per-watt metric. The MI300X also offers a lower transistor density on a smaller die, which could imply different thermal or manufacturing characteristics.

The choice hinges on whether the 16.3% performance gap matters more than the MI300X’s alternative strengths. If the workload is dominated by the exact type of compute measured by Geekbench OpenCL, the NVIDIA B300 SXM6 AC is the only logical pick. If the workload leverages the MI300X’s higher raw FP32 throughput or if power constraints are a factor, the AMD card could be viable, but the data does not support it as the faster overall option.

Specification Differences

| Specification | NVIDIA B300 SXM6 AC | AMD Instinct MI300X |

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

| Chip | GB110 | Aqua Vanjaram |

| Architecture | Blackwell Ultra | CDNA 3.0 |

| Transistors | 208,000 million | 153,000 million |

| Die Size | 1628 mm² | 1017 mm² |

| Transistor Density | 127.8M / mm² | 150.4M / mm² |

| Base Clock | 1665 MHz | 1000 MHz |

| Boost Clock | 2032 MHz | 2100 MHz |

| Memory Size | 288 GB | 192 GB |

| Memory Type | HBM3e | HBM3 |

| Memory Clock | 2000 MHz (8 Gbps effective) | 1300 MHz (5.2 Gbps effective) |

| Memory Bandwidth | 8.19 TB/s | 5.32 TB/s |

| Shading Units | 18,944 | 19,456 |

| TMUs | 592 | 1,216 |

| ROPs | 24 | 0 |

| Tensor Cores | 592 | null |

| Pixel Rate | 48.77 GPixel/s | 0 MPixel/s |

| Texture Rate | 1,202.9 GTexel/s | 2,553.6 GTexel/s |

| FP32 / FP16 | 76.99 TFLOPS | 81.72 TFLOPS |

| TDP | 1100 W | 750 W |

| Slot Width | SXM Module | OAM Module |

| Suggested PSU | 1500 W | 1150 W |

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

| Release Date | 2025-09-10 | 2023-12-05 |