AMD Instinct MI355X vs NVIDIA B300 Comparison

Head-to-Head Benchmarks

The recorded data for both accelerators shows a tie across all measured workloads, with zero wins recorded for either part. The average benchmark score for the AMD Instinct MI355X is 0, and the NVIDIA B300 also posts an average benchmark score of 0, placing both at the 50th percentile against all GPUs in the database. With no head-to-head benchmark entries and no nearest rivals listed, the quantitative comparison rests entirely on the architectural and specification records rather than measured performance deltas.

The FP32 compute figures are the closest point of comparison. The AMD Instinct MI355X delivers 78.64 TFLOPS of FP32 throughput, while the NVIDIA B300 posts 76.99 TFLOPS. The difference is 1.65 TFLOPS in favor of AMD, a margin of roughly 2.1 percent. This is a narrow lead, and benchmark results indicate the two accelerators fall within the same performance tier for general compute workloads that rely on FP32 math. Texture rate favors AMD more clearly, with the MI355X recording 2,457.6 GTexel/s against 1,202.9 GTexel/s for the B300. That is more than double the fill rate, a substantial advantage for workloads that stress texture sampling and filtering. Pixel rate, however, reverses the picture. The B300 records 48.77 GPixel/s, while the MI355X shows 0 MPixel/s, reflecting a fundamental difference in how the two architectures handle rasterization output.

FP16 compute shows a dramatic divergence. The NVIDIA B300 delivers 1,231.8 TFLOPS of FP16 throughput, while the AMD Instinct MI355X records 78.64 TFLOPS with a 1:1 ratio to FP32. The B300’s FP16 figure is roughly 15.7 times higher, a decisive edge for AI training and inference workloads that operate in reduced precision. This single metric separates the two parts more than any other recorded specification. The AMD part’s 1:1 FP16 to FP32 ratio indicates it treats both precisions with equal throughput, whereas the B300’s 16:1 ratio shows a heavy bias toward FP16 compute, consistent with a design optimized for neural network math rather than general-purpose floating point.

Architecture Differences

The two accelerators come from different foundry processes and architectural generations. The AMD Instinct MI355X uses the CDNA 4.0 architecture built on a 3 nm process at TSMC, while the NVIDIA B300 uses the Blackwell Ultra architecture on a 5 nm process, also at TSMC. The AMD chip, designated MI350 256CU, packs 185,000 million transistors onto a 2380 mm² die, yielding a transistor density of 77.7 million transistors per square millimeter. The NVIDIA GB110 chip holds 104,000 million transistors, with no die size or density recorded in the data. AMD’s transistor count is 81,000 million higher than NVIDIA’s, and the smaller 3 nm node explains how that larger count fits into a dense package.

Memory configurations differ substantially. The MI355X carries 288 GB of HBM3e memory across an 8192-bit bus, delivering 8.19 TB/s of bandwidth. The B300 carries 144 GB of HBM3e on a 4096-bit bus, delivering 4.10 TB/s. AMD has exactly twice the memory capacity, twice the bus width, and twice the bandwidth. Both parts use HBM3e and run memory at 2000 MHz with 8 Gbps effective data rate, so the bandwidth difference comes purely from the wider bus and larger capacity.

The compute unit layouts are distinct. The MI355X has 16,384 shading units and 1,024 texture mapping units, with no ROPs recorded. The B300 has 18,944 shading units, 592 texture mapping units, and 24 ROPs. NVIDIA has 2,560 more shading units but 432 fewer TMUs. The B300 also records 592 tensor cores, while the MI355X records no tensor core count. The AMD part has no pixel rate and no ROPs, while the B300 has a functional rasterization pipeline with 24 ROPs. Clock speeds favor NVIDIA: the B300 runs at 1665 MHz base and 2032 MHz boost, while the MI355X runs at 1000 MHz base and 2400 MHz boost. The AMD part has a higher boost clock by 368 MHz, but the NVIDIA part starts from a much higher base clock. Power envelopes are identical, with both parts rated at 1400 W TDP and a suggested PSU of 1800 W. The AMD part uses an OAM module slot width with no power connectors listed, while the NVIDIA part uses an SXM module slot width with no power connector data.

Release timing places the AMD part first. The MI355X has a release date of 2025-06-11, and the B300 follows with a release date of 2025-09-10. The NVIDIA part is marked as Active in production status, while the AMD part has no production status recorded. The AMD predecessor is listed as Radeon Instinct, and the NVIDIA predecessor is Server Hopper. The B300 also has a recorded successor, Server Rubin, while the MI355X successor field is empty.

The Verdict

The recorded data supports a clear division of roles. The NVIDIA B300 is the stronger choice for FP16-heavy compute, specifically AI and machine learning workloads, based on its 1,231.8 TFLOPS FP16 throughput against the MI355X’s 78.64 TFLOPS. The B300 also has functional rasterization with 24 ROPs and a pixel rate of 48.77 GPixel/s, whereas the MI355X has no ROPs and no pixel output. For any workload that requires pixel processing, the B300 is the only viable option from this data.

The AMD Instinct MI355X wins on memory capacity and bandwidth. Its 288 GB of HBM3e and 8.19 TB/s bandwidth are exactly double the B300’s 144 GB and 4.10 TB/s. For model training or inference with very large datasets that exceed 144 GB, the MI355X avoids capacity constraints. Its texture rate of 2,457.6 GTexel/s is more than double the B300’s 1,202.9 GTexel/s, which favors workloads with heavy texture sampling. FP32 throughput is marginally higher on the MI355X at 78.64 TFLOPS versus 76.99 TFLOPS, a small but real edge for general compute.

The B300 uses a 5 nm process with 104,000 million transistors, while the MI355X uses a 3 nm process with 185,000 million transistors. The AMD part has a larger die at 2380 mm² and higher transistor density. The B300 counters with more shading units, 18,944 versus 16,384, and a higher base clock of 1665 MHz versus 1000 MHz. The MI355X has a higher boost clock of 2400 MHz versus 2032 MHz, but the B300’s base clock advantage suggests more sustained performance under load, assuming clock behavior follows the recorded figures.

FAQ

Q: Which accelerator has more FP32 compute power?

A: The AMD Instinct MI355X records 78.64 TFLOPS of FP32 throughput, while the NVIDIA B300 records 76.99 TFLOPS. The MI355X holds a 1.65 TFLOPS lead.

Q: How do the two parts compare in FP16 performance?

A: The NVIDIA B300 delivers 1,231.8 TFLOPS of FP16 throughput, which is far above the AMD Instinct MI355X’s 78.64 TFLOPS. The B300’s FP16 figure is roughly 15.7 times higher.

Q: What is the memory capacity difference?

A: The AMD Instinct MI355X has 288 GB of HBM3e memory, while the NVIDIA B300 has 144 GB. The MI355X also has an 8192-bit bus versus the B300’s 4096-bit bus, and 8.19 TB/s bandwidth versus 4.10 TB/s.

Q: Do both cards have the same power requirement?

A: Yes. Both the AMD Instinct MI355X and the NVIDIA B300 are rated at 1400 W TDP and list a suggested PSU of 1800 W.

Q: Which part has a functional rasterization pipeline?

A: The NVIDIA B300 has 24 ROPs and records a pixel rate of 48.77 GPixel/s. The AMD Instinct MI355X records 0 ROPs and a pixel rate of 0 MPixel/s.

Q: What are the release dates for these accelerators?

A: The AMD Instinct MI355X has a release date of 2025-06-11, and the NVIDIA B300 has a release date of 2025-09-10.

Where Each One Wins

The AMD Instinct MI355X wins in memory-related metrics. It carries 288 GB of HBM3e, which is double the B300’s 144 GB. Its 8.19 TB/s bandwidth is double the B300’s 4.10 TB/s. The 8192-bit bus is twice as wide as the B300’s 4096-bit bus. These figures point to workloads where capacity and bandwidth dominate, such as holding very large model weights or working with massive datasets that do not fit in the B300’s smaller memory pool. The MI355X also wins on texture rate, recording 2,457.6 GTexel/s against the B300’s 1,202.9 GTexel/s. This suggests an advantage in texture-intensive compute tasks, even though the MI355X has no ROPs and cannot output pixels.

The NVIDIA B300 wins on reduced-precision compute. Its 1,231.8 TFLOPS FP16 throughput is the single largest performance gap in the record, making it the clear choice for AI training, inference, and other FP16-centric workloads. The B300 also wins on shading unit count with 18,944 units versus 16,384, and it has 592 tensor cores while the MI355X has no tensor core count recorded. The B300’s 592 TMUs are lower than the MI355X’s 1,024, but the B300 compensates with a higher base clock of 1665 MHz versus 1000 MHz. The B300’s pixel rate of 48.77 GPixel/s and 24 ROPs give it a functional display and rasterization path, which the MI355X lacks entirely.

The FP32 comparison is close. The MI355X leads with 78.64 TFLOPS versus 76.99 TFLOPS, but the margin is under 3 percent. In practical terms, the data shows neither part has a decisive FP32 advantage. The B300’s FP16 ratio of 16:1 versus the MI355X’s 1:1 makes the NVIDIA part the specialized choice for mixed-precision training, while the MI355X’s balanced FP16 to FP32 ratio offers consistent throughput across both precisions.

Specification Differences

The AMD Instinct MI355X and NVIDIA B300 differ across nearly every recorded specification except power draw and interface. Both use PCIe 5.0 x16, both are rated at 1400 W TDP, and both list a suggested PSU of 1800 W. Both use HBM3e memory running at 2000 MHz with 8 Gbps effective data rate. Both have no display outputs and no recorded DirectX, OpenGL, or Vulkan API support.

The process node differs: AMD uses 3 nm, NVIDIA uses 5 nm, both at TSMC. The MI355X chip is MI350 256CU with 185,000 million transistors on a 2380 mm² die, while the B300 chip is GB110 with 104,000 million transistors and no die size recorded. Transistor density for the MI355X is 77.7 million per square millimeter, while the B300 has no density figure.

Compute resources differ in distribution. The MI355X has 16,384 shading units, 1,024 TMUs, and 0 ROPs. The B300 has 18,944 shading units, 592 TMUs, and 24 ROPs. The MI355X has no tensor core count, while the B300 has 592 tensor cores. Texture rate favors the MI355X at 2,457.6 GTexel/s versus 1,202.9 GTexel/s. Pixel rate favors the B300 at 48.77 GPixel/s versus 0 MPixel/s. FP32 favors the MI355X at 78.64 TFLOPS versus 76.99 TFLOPS. FP16 heavily favors the B300 at 1,231.8 TFLOPS versus 78.64 TFLOPS.

Clock speeds differ. The MI355X has a base clock of 1000 MHz and a boost clock of 2400 MHz. The B300 has a base clock of 1665 MHz and a boost clock of 2032 MHz. Memory clocks are identical at 2000 MHz and 8 Gbps effective. Memory capacity, bus width, and bandwidth all favor the MI355X: 288 GB, 8192 bit, and 8.19 TB/s versus 144 GB, 4096 bit, and 4.10 TB/s. The MI355X uses an OAM Module slot width with no power connectors, while the B300 uses an SXM Module slot width with no power connector data. The MI355X has no production status recorded, while the B300 is marked Active. Release dates differ by three months, with the MI355X on 2025-06-11 and the B300 on 2025-09-10. The MI355X predecessor is Radeon Instinct, and the B300 predecessor is Server Hopper, with Server Rubin listed as the B300 successor.