AMD Instinct MI355X vs AMD Radeon Instinct MI300 Comparison

FAQ

Q: What are the two products compared here?

A: This comparison covers the AMD Instinct MI355X and the AMD Radeon Instinct MI300. The MI355X is built on the CDNA 4.0 architecture with the MI350 256CU chip, while the MI300 uses the CDNA 3.0 architecture with the Aqua Vanjaram chip.

Q: Which product has the larger memory capacity?

A: The AMD Instinct MI355X has 288 GB of HBM3e memory, which is more than double the 128 GB of HBM3 memory found on the AMD Radeon Instinct MI300.

Q: How do the two GPUs compare in terms of FP32 compute?

A: The MI355X delivers 78.64 TFLOPS of FP32 compute, while the MI300 delivers 47.87 TFLOPS. That puts the MI355X ahead by roughly 64% in standard single-precision throughput.

Q: What is the difference in memory bandwidth between the two?

A: The MI355X provides 8.19 TB/s of bandwidth, whereas the MI300 provides 6.55 TB/s. The newer part offers a higher memory throughput, reflecting both a faster memory type and higher effective clock.

Q: Which GPU has a higher boost clock?

A: The MI355X boosts to 2400 MHz, while the MI300 boosts to 1700 MHz. The base clocks are identical at 1000 MHz for both.

Q: Do both GPUs use the same process node?

A: No. The MI355X is manufactured on a 3 nm process at TSMC, while the MI300 is on a 5 nm process at TSMC. The MI355X also has a larger die size at 2380 mm² compared to the MI300's 1017 mm².

Architecture Differences

The AMD Instinct MI355X and AMD Radeon Instinct MI300 represent two successive generations of AMD's data center accelerators. The MI355X is built on the CDNA 4.0 architecture, while the MI300 is based on CDNA 3.0. This generational shift brings substantial changes in chip design, manufacturing, and feature set.

The most visible difference is the process node. The MI355X uses a 3 nm process at TSMC, whereas the MI300 uses a 5 nm process at the same foundry. Despite the smaller node, the MI355X has a significantly larger die: 2380 mm² versus 1017 mm² for the MI300. Transistor counts also differ, with the MI355X containing 185,000 million transistors and the MI300 containing 153,000 million. Interestingly, the transistor density is lower on the newer chip: 77.7M per mm² for the MI355X versus 150.4M per mm² for the MI300. This indicates that the CDNA 4.0 design uses more die area per transistor, likely due to a larger compute and memory architecture.

The chip designations also differ. The MI355X uses the MI350 256CU chip, which suggests a specific compute unit configuration, while the MI300 uses the Aqua Vanjaram chip. The MI355X has 16,384 shading units and 1,024 texture mapping units, compared to the MI300's 14,080 shading units and 880 TMUs. Both parts have zero ROPs and zero pixel rate, which is consistent with their role as compute accelerators with no display output.

Memory architecture shows a clear generational leap. The MI355X uses HBM3e memory with a capacity of 288 GB and an 8192-bit bus, achieving a bandwidth of 8.19 TB/s. The MI300 uses HBM3 memory with a capacity of 128 GB, also on an 8192-bit bus, but with a lower bandwidth of 6.55 TB/s. The memory clock differs as well: the MI355X runs at 2000 MHz (8 Gbps effective), while the MI300 runs at 1600 MHz (6.4 Gbps effective). The MI355X has no PCIe power connectors and is an OAM module, while the MI300 uses 2x 8-pin connectors. Both use a PCIe 5.0 x16 bus interface and have no display outputs.

The FP16 compute rates also differ significantly. The MI355X achieves 78.64 TFLOPS FP16 at a 1:1 ratio with FP32, indicating a straightforward execution path. The MI300 achieves 383.0 TFLOPS FP16 at an 8:1 ratio, meaning it uses a different precision strategy that heavily favors packed half-precision operations. This architectural divergence suggests the MI300 was tuned for workloads that can exploit dense FP16 math, while the MI355X offers more balanced precision scaling.

Head-to-Head Benchmarks

The recorded data shows no direct benchmark scores for either GPU, and the nearest rivals list is empty. However, the specification data provides a basis for performance comparisons across several key metrics. The most decisive difference is in FP32 compute throughput. The MI355X delivers 78.64 TFLOPS, which is 64% higher than the MI300's 47.87 TFLOPS. This is a substantial lead for the newer part in general-purpose single-precision workloads.

In FP16 compute, the comparison is more complex due to different ratio implementations. The MI300's 383.0 TFLOPS at an 8:1 ratio is roughly 4.9 times higher than the MI355X's 78.64 TFLOPS at a 1:1 ratio. This means that in workloads specifically designed for dense FP16 math, the MI300 has a clear advantage in raw throughput. However, the MI355X's 1:1 ratio indicates that its FP16 performance does not require a precision penalty, which may simplify programming and yield more predictable results in mixed-precision scenarios.

Texture rate also favors the MI355X. It achieves 2,457.6 GTexel/s, compared to the MI300's 1,496.0 GTexel/s. This is roughly 64% higher, consistent with the FP32 scaling and reflective of the higher shading unit and TMU counts. Pixel rate is zero for both, as neither GPU has ROPs.

Memory bandwidth is another clear win for the MI355X. Its 8.19 TB/s exceeds the MI300's 6.55 TB/s by about 25%. This higher bandwidth, combined with the larger 288 GB capacity, gives the MI355X a meaningful advantage in memory-bound workloads such as large model inference or training datasets that exceed the MI300's 128 GB capacity.

The boost clock difference also favors the MI355X. It boosts to 2400 MHz, which is 41% higher than the MI300's 1700 MHz. Base clocks are identical at 1000 MHz, so the MI355X has a much wider clock headroom. This higher clock, along with the larger shading unit count, contributes to its compute lead.

The MI355X also has a higher thermal design power at 1400 W, compared to the MI300's 600 W. This higher power envelope supports its higher clocks and larger die. The suggested PSU for the MI355X is 1800 W, while the MI300 suggests 1000 W. These figures indicate that the MI355X requires more substantial power delivery infrastructure.

Specification Differences

The two GPUs differ across nearly every major specification category. The process node is 3 nm for the MI355X versus 5 nm for the MI300. Die size is 2380 mm² versus 1017 mm². Transistor count is 185,000 million versus 153,000 million. Transistor density is 77.7M per mm² versus 150.4M per mm².

The clock specifications differ in boost and memory clocks. The MI355X has a boost clock of 2400 MHz, while the MI300 has a boost clock of 1700 MHz. Base clocks are both 1000 MHz. Memory clock is 2000 MHz (8 Gbps effective) for the MI355X and 1600 MHz (6.4 Gbps effective) for the MI300.

Memory capacity is 288 GB of HBM3e for the MI355X versus 128 GB of HBM3 for the MI300. Both have an 8192-bit bus, but bandwidth is 8.19 TB/s versus 6.55 TB/s. Shading units are 16,384 versus 14,080. TMUs are 1,024 versus 880. ROPs are 0 for both. Pixel rate is 0 MPixel/s for both.

Texture rate is 2,457.6 GTexel/s for the MI355X and 1,496.0 GTexel/s for the MI300. FP32 is 78.64 TFLOPS versus 47.87 TFLOPS. FP16 is 78.64 TFLOPS (1:1) versus 383.0 TFLOPS (8:1). TDP is 1400 W versus 600 W. The MI355X is an OAM Module with no power connectors, while the MI300 has 2x 8-pin connectors. Suggested PSU is 1800 W versus 1000 W.

Dimensions differ. The MI355X is 102 mm long and 165 mm wide. The MI300 is 267 mm long and 111 mm high. The MI355X has no listed height, and the MI300 has no listed width. The MI355X was released on 2025-06-11, while the MI300 was released on 2023-01-03. The MI355X lists its predecessor as Radeon Instinct, and the MI300 lists its predecessor as FirePro Data Center. The MI355X architecture is CDNA 4.0, and the MI300 is CDNA 3.0. The MI355X chip is MI350 256CU, and the MI300 chip is Aqua Vanjaram.

The Verdict

The data indicates that the AMD Instinct MI355X is the stronger part for most compute-heavy workloads. Its FP32 throughput of 78.64 TFLOPS is 64% ahead of the MI300's 47.87 TFLOPS. Its memory bandwidth of 8.19 TB/s is 25% higher, and its memory capacity of 288 GB is more than double the MI300's 128 GB. Its boost clock of 2400 MHz is 41% higher than the MI300's 1700 MHz. For workloads that rely on single-precision math, high memory bandwidth, or large memory footprints, the MI355X is clearly the better choice.

The MI300 does hold one notable advantage: FP16 throughput. Its 383.0 TFLOPS at an 8:1 ratio is roughly 4.9 times higher than the MI355X's 78.64 TFLOPS at a 1:1 ratio. This makes the MI300 more suitable for applications that are specifically optimized for dense half-precision operations and can tolerate the precision ratio. However, the MI355X's 1:1 ratio offers simpler precision handling and avoids the throughput penalty that the MI300's 8:1 approach might impose in mixed-precision workflows.

The MI300 also has a lower power draw at 600 W versus the MI355X's 1400 W, and a lower suggested PSU at 1000 W versus 1800 W. For deployments where power delivery is constrained, the MI300 is the more manageable option. Its smaller die size of 1017 mm² and lower transistor count also indicate a less complex manufacturing footprint.

The MI355X is the newer product, released in June 2025, while the MI300 was released in January 2023. The MI355X uses the newer CDNA 4.0 architecture, a 3 nm process, and HBM3e memory. It is the higher-performance, higher-power option. The MI300, with its CDNA 3.0 architecture, 5 nm process, and HBM3 memory, remains a capable alternative for FP16-heavy workloads and lower-power deployments. The choice between the two should be driven by the specific precision requirements and power constraints of the deployment environment.