AMD Instinct MI325X vs AMD Instinct MI350P Comparison

AMD Instinct MI325X and AMD Instinct MI350P are both accelerators in the Instinct (MIx) generation, but they represent distinct design points within AMD's data center GPU lineup. The MI325X, built on the CDNA 3.0 architecture, prioritizes massive memory capacity and raw compute throughput, while the MI350P, using the newer CDNA 4.0 architecture, focuses on a more efficient, higher-bandwidth package. The recorded data for both parts shows a percentile rank of 50 against all GPUs in the database, with no benchmark scores or nearest rivals listed, meaning the analysis here is based entirely on their architectural and specification differences.

Where Each One Wins

The MI325X is positioned for workloads where memory capacity and raw floating-point performance are the primary constraints. Its 256 GB of HBM3e memory is substantially larger, which allows for larger datasets and models to reside on a single accelerator without spilling to system memory. The FP32 and FP16 throughput of 81.72 TFLOPS (1:1) on the MI325X is more than double that of the MI350P, indicating a clear advantage for compute-bound operations that are not memory-bandwidth limited. This makes the MI325X the stronger candidate for training large neural networks or running simulations where the model weights and activations can consume significant memory.

The MI350P wins on memory bandwidth and power efficiency. Its 8.19 TB/s of bandwidth is a 33% increase over the MI325X's 6.14 TB/s, which is critical for memory-bound tasks like inference with large batch sizes or processing high-resolution data streams. The MI350P also operates at a significantly lower thermal design power of 600 W, versus 1000 W for the MI325X, and uses a more conventional dual-slot form factor with a single 16-pin power connector. This suggests the MI350P is intended for denser, more power-conscious deployments where the higher bandwidth per watt is more valuable than raw compute or capacity.

Architecture Differences

The two accelerators are built on different architecture generations and manufacturing processes. The MI325X uses CDNA 3.0 and is fabricated on a 5 nm process at TSMC, with a transistor count of 153,000 million on a die size of 1017 mm². The MI350P moves to CDNA 4.0 and a 3 nm process, also from TSMC, with a notably lower transistor count of 73,000 million on a larger die size of 1190 mm². The transistor density figures reflect this shift: the MI325X has a density of 150.4M transistors per mm², while the MI350P is at 61.3M per mm². This indicates that the MI350P's design is not about maximizing transistor count but rather about optimizing the memory system and clock speeds while reducing power consumption.

The chip designations differ as well, with the MI325X using the "Aqua Vanjaram" chip and the MI350P using "MI350 128CU". The MI350P's name suggests a compute unit count of 128, which aligns with its lower shading unit count of 8192, while the MI325X has 19456 shading units. The clock speeds are broadly similar, with a base of 1000 MHz for both, but the boost clock is slightly higher on the MI350P at 2200 MHz versus 2100 MHz on the MI325X. Both use HBM3e memory with an identical 8192-bit bus width, but the memory clock differs, with the MI350P running at 2000 MHz (8 Gbps effective) and the MI325X at 1500 MHz (6 Gbps effective).

Head-to-Head Benchmarks

Since the database contains no head-to-head benchmark entries or average benchmark scores for either accelerator, direct performance comparisons must be inferred from the specification data. The most significant numerical advantage for the MI325X is in compute throughput. Its FP32 and FP16 performance of 81.72 TFLOPS is 126.8% higher than the MI350P's 36.04 TFLOPS. This is a massive delta in raw compute capability, meaning any workload that is compute-bound will see a substantial performance lead on the MI325X, provided the memory capacity is sufficient.

The MI350P counters with a memory bandwidth advantage. Its 8.19 TB/s is 33.4% higher than the MI325X's 6.14 TB/s. In memory-bound scenarios, where the compute units are waiting on data, this higher bandwidth can translate to a meaningful performance win for the MI350P. The texture rate also differs, with the MI325X delivering 2,553.6 GTexel/s compared to the MI350P's 1,126.4 GTexel/s, a 126.7% difference that again favors the MI325X. Both parts have a pixel rate of 0 MPixel/s and no display outputs, indicating they are purely compute accelerators with no graphics output functionality.

Specification Differences

The two accelerators differ across nearly every major specification category. The most obvious difference is memory size: the MI325X has 256 GB, while the MI350P has 144 GB. The memory type is the same (HBM3e) and the bus width is the same (8192 bit), but the bandwidth is higher on the MI350P. The chip design, architecture, and process node all differ, as detailed above. The shading unit count is 19456 for the MI325X versus 8192 for the MI350P, and the texture mapping units are 1216 versus 512, respectively.

Power and physical characteristics also diverge significantly. The MI325X has a TDP of 1000 W and is an OAM Module with no power connectors, requiring an external power delivery system. The MI350P has a TDP of 600 W, is a dual-slot card with a single 16-pin power connector, and has defined dimensions of 267 mm in length, 111 mm in height, and 40 mm in width. The suggested power supply is 1400 W for the MI325X and 1000 W for the MI350P. Both use a PCIe 5.0 x16 bus interface, have no display outputs, and do not support DirectX, OpenGL, or Vulkan APIs, which is expected for data center accelerators. The release dates are also different, with the MI325X releasing on 2024-10-09 and the MI350P on 2026-05-06.

FAQ

Q: Which accelerator has more memory?

A: The AMD Instinct MI325X has 256 GB of HBM3e memory, while the AMD Instinct MI350P has 144 GB of HBM3e memory.

Q: What is the memory bandwidth difference?

A: The MI350P has a higher memory bandwidth of 8.19 TB/s, compared to the MI325X's 6.14 TB/s, despite the MI325X having a larger memory capacity.

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

A: The MI325X delivers 81.72 TFLOPS of FP32 performance, which is more than double the MI350P's 36.04 TFLOPS.

Q: What are the power requirements for each?

A: The MI325X has a TDP of 1000 W and requires a suggested power supply of 1400 W, while the MI350P has a TDP of 600 W and a suggested power supply of 1000 W.

Q: Are there any differences in physical form factor?

A: Yes, the MI325X is an OAM Module with no power connectors, while the MI350P is a dual-slot card with a single 16-pin power connector and specific dimensions of 267 mm length, 111 mm height, and 40 mm width.

Q: Do both accelerators use the same manufacturing process?

A: No, the MI325X uses a 5 nm process, while the MI350P uses a 3 nm process, both from TSMC.

The Verdict

The data indicates a clear split in intended use cases. The AMD Instinct MI325X is the choice for compute-heavy workloads that need maximum memory capacity and raw floating-point throughput. Its 81.72 TFLOPS of FP16/FP32 performance and 256 GB of memory make it suited for large-scale training runs and complex simulations where the entire model can fit on the accelerator. The higher TDP and OAM form factor suggest it is designed for systems with dedicated power delivery and cooling.

The AMD Instinct MI350P is the choice for memory-bandwidth-bound and power-constrained environments. Its 8.19 TB/s bandwidth is the highest among the two, and its 600 W TDP is significantly lower, making it easier to deploy in dense server configurations. The smaller memory capacity of 144 GB and lower compute throughput mean it is less suited for the largest training jobs, but its higher boost clock of 2200 MHz and more efficient process node could provide advantages in latency-sensitive inference tasks. The dual-slot design with a standard 16-pin connector also simplifies integration compared to the OAM module of the MI325X.