AMD Instinct MI300A vs AMD Instinct MI355X Comparison

AMD Instinct MI300A and AMD Instinct MI355X are both OAM Module accelerators built for dense compute environments, yet they represent different generations of CDNA architecture. The MI300A is built on CDNA 3.0 with a 5 nm process, while the MI355X moves to CDNA 4.0 on a 3 nm node. Both use an 8192-bit memory bus, but the memory type, capacity, and bandwidth differ substantially. The MI355X carries 288 GB of HBM3e with 8.19 TB/s of bandwidth, compared to the MI300A’s 128 GB of HBM3 and 5.32 TB/s. Compute resources also scale upward: the MI355X has 16,384 shading units and 1,024 TMUs, versus 14,592 shading units and 912 TMUs on the MI300A. The MI355X boosts to 2400 MHz, higher than the MI300A’s 2100 MHz boost clock, and delivers 78.64 TFLOPS FP32 versus 61.29 TFLOPS. Power requirements scale as well, with the MI355X rated at 1400 W and a suggested 1800 W PSU, while the MI300A is rated at 750 W with a suggested 1150 W PSU.

FAQ

Q: What is the process node difference between the MI300A and MI355X?

A: The MI300A is fabricated on a 5 nm process at TSMC, while the MI355X uses a 3 nm process, also at TSMC.

Q: How much memory does each accelerator have?

A: The MI300A has 128 GB of HBM3 memory, while the MI355X has 288 GB of HBM3e memory. Both use an 8192-bit bus, but the MI355X achieves 8.19 TB/s bandwidth versus 5.32 TB/s on the MI300A.

Q: Which accelerator has a higher boost clock?

A: The MI355X boosts to 2400 MHz, whereas the MI300A boosts to 2100 MHz. Both have a base clock of 1000 MHz.

Q: How do the FP32 compute figures compare?

A: The MI355X delivers 78.64 TFLOPS FP32, which is higher than the MI300A’s 61.29 TFLOPS FP32. The MI355X also lists FP16 at 78.64 TFLOPS (1:1), while the MI300A does not list an FP16 figure.

Q: What are the physical dimensions of the MI355X?

A: The MI355X measures 102 mm (4 inches) in length and 165 mm (6.5 inches) in width. The MI300A has no listed physical dimensions.

Q: Do either of these accelerators support graphics APIs like DirectX or Vulkan?

A: No. Both the MI300A and MI355X list DirectX, OpenGL, and Vulkan as N/A, and both have no display outputs.

Architecture Differences

The MI300A and MI355X are separated by a full architecture generation. The MI300A uses CDNA 3.0, while the MI355X uses CDNA 4.0. This generation change brings a shift in process technology: the MI300A is built on a 5 nm node, while the MI355X moves to a 3 nm node, both at TSMC. The transistor count rises from 153,000 million on the MI300A to 185,000 million on the MI355X. Die size grows from 1017 mm² to 2380 mm², which is notable because the transistor density actually drops from 150.4M per mm² on the MI300A to 77.7M per mm² on the MI355X. The larger die with a lower density suggests a different design strategy, even though the node is smaller.

The chip names also differ. The MI300A uses the chip name “Aqua Vanjaram,” while the MI355X uses “MI350 256CU.” The MI355X’s chip name explicitly references 256 compute units, which aligns with its higher shading unit count of 16,384 versus 14,592 on the MI300A. Texture mapping units increase from 912 to 1,024. Neither accelerator has ROPs, with pixel rate listed as 0 MPixel/s for both. Tensor cores and ray tracing cores are not listed for either part, and both support PCIe 5.0 x16 as the bus interface.

Memory architecture changes with the generation. The MI300A uses HBM3 with a 1300 MHz memory clock, which the database records as 5.2 Gbps effective. The MI355X uses HBM3e with a 2000 MHz memory clock, recorded as 8 Gbps effective. Bus width stays at 8192 bit for both. The MI300A’s texture rate is 1,915.2 GTexel/s, while the MI355X reaches 2,457.6 GTexel/s. Both accelerators have no display outputs and no power connectors, relying on the OAM Module slot for power delivery. The MI355X has a suggested PSU of 1800 W versus 1150 W for the MI300A, and its TDP is 1400 W versus 750 W. The MI355X also lists physical dimensions of 102 mm by 165 mm, while the MI300A has no listed dimensions.

Where Each One Wins

The MI355X wins on raw compute throughput. Its FP32 figure of 78.64 TFLOPS is higher than the MI300A’s 61.29 TFLOPS, a difference of roughly 17.35 TFLOPS. The MI355X also has a higher texture rate at 2,457.6 GTexel/s versus 1,915.2 GTexel/s, which corresponds to its larger TMU count. In workloads that scale with shading units, the MI355X’s 16,384 shading units give it an advantage over the 14,592 on the MI300A. The boost clock is also higher on the MI355X, 2400 MHz versus 2100 MHz, which helps sustained compute performance.

Memory capacity and bandwidth favor the MI355X significantly. With 288 GB of HBM3e and 8.19 TB/s bandwidth, the MI355X can hold larger working sets and move data faster than the MI300A, which has 128 GB of HBM3 and 5.32 TB/s. For large model inference or training runs where memory footprint is a limiting factor, the MI355X is the clear choice. The MI355X also uses HBM3e, a newer memory type, and runs its memory at 2000 MHz versus 1300 MHz on the MI300A.

The MI300A retains advantages in transistor density and power draw. Its 150.4M transistors per mm² is nearly double the MI355X’s 77.7M per mm², indicating a more compact use of silicon area per transistor. The MI300A’s TDP of 750 W is exactly half of the MI355X’s 1400 W, and its suggested PSU of 1150 W is lower than the 1800 W suggested for the MI355X. In power-constrained environments, the MI300A delivers 61.29 TFLOPS FP32 at a lower power envelope, which may be preferable when system-level power budgets are tight. The MI300A also carries a smaller die, 1017 mm² versus 2380 mm², which could affect manufacturing yield considerations, though the database does not provide yield data.

Specification Differences

The two accelerators differ across process, architecture, chip name, transistor count, die size, density, clocks, memory, compute units, and power. The MI300A is CDNA 3.0 on 5 nm with the Aqua Vanjaram chip, while the MI355X is CDNA 4.0 on 3 nm with the MI350 256CU chip. Transistors increase from 153,000 million to 185,000 million, and die size increases from 1017 mm² to 2380 mm². Transistor density drops from 150.4M per mm² to 77.7M per mm².

Base clocks are the same at 1000 MHz, but boost clocks differ: 2100 MHz on the MI300A and 2400 MHz on the MI355X. Memory clocks differ as well, with the MI300A at 1300 MHz (5.2 Gbps effective) and the MI355X at 2000 MHz (8 Gbps effective). Memory size goes from 128 GB HBM3 to 288 GB HBM3e. Bandwidth increases from 5.32 TB/s to 8.19 TB/s. Bus width remains 8192 bit on both.

Shading units increase from 14,592 to 16,384, and TMUs increase from 912 to 1,024. ROPs are 0 on both. Pixel rate is 0 MPixel/s on both. Texture rate rises from 1,915.2 GTexel/s to 2,457.6 GTexel/s. FP32 rises from 61.29 TFLOPS to 78.64 TFLOPS. The MI355X lists FP16 at 78.64 TFLOPS (1:1), while the MI300A does not list FP16. TDP rises from 750 W to 1400 W. Suggested PSU rises from 1150 W to 1800 W. Both use OAM Module slot width, neither has power connectors, and both use PCIe 5.0 x16. Both have no display outputs and no graphics API support. The MI355X lists dimensions of 102 mm by 165 mm, while the MI300A does not list dimensions. Release dates differ: the MI300A launched on 2023-12-05 and the MI355X on 2025-06-11. Neither lists a launch MSRP.

Head-to-Head Benchmarks

The database shows no recorded head-to-head benchmark runs for these two accelerators, and neither part has an average benchmark score or nearest rival entries. The comparison rests on the specification-level measurements that are recorded. The largest single numerical gap is in memory bandwidth. The MI355X delivers 8.19 TB/s, which is 2.87 TB/s higher than the MI300A’s 5.32 TB/s. That is a 53.9% increase in bandwidth, and when combined with the capacity jump from 128 GB to 288 GB, the MI355X is positioned for workloads that are memory-bound. The memory clock difference contributes to this: 2000 MHz versus 1300 MHz, and the effective data rate rises from 5.2 Gbps to 8 Gbps.

FP32 compute shows a 17.35 TFLOPS gap. The MI355X’s 78.64 TFLOPS is 28.3% higher than the MI300A’s 61.29 TFLOPS. Texture rate follows a similar pattern, with the MI355X at 2,457.6 GTexel/s versus 1,915.2 GTexel/s, a 542.4 GTexel/s difference. The shading unit count difference is 1,792 units, and the TMU count difference is 112 units. The boost clock gap is 300 MHz. Each of these specification deltas points in the same direction: the MI355X has a higher peak throughput in every measured compute category.

The MI300A’s recorded advantages are in transistor density and power. The density of 150.4M per mm² versus 77.7M per mm² is a 72.7M per mm² difference. The TDP of 750 W versus 1400 W is a 650 W difference, and the suggested PSU drops from 1800 W to 1150 W. For deployments where power delivery is capped, the MI300A’s lower TDP is the only recorded power advantage between the two parts. Neither accelerator has a listed FP16 value on the MI300A, while the MI355X records FP16 at 78.64 TFLOPS with a 1:1 ratio to FP32, which is a notable capability difference for mixed-precision workloads.

The release timeline also separates these parts. The MI300A launched on 2023-12-05, while the MI355X launched on 2025-06-11. The 3 nm node on the MI355X, combined with the larger die and higher transistor count, explains the higher compute and memory figures. The die size increase from 1017 mm² to 2380 mm² is the largest physical change, though the density drop indicates that the MI355X uses its area differently than the MI300A. Both parts share the same 8192-bit bus, same PCIe 5.0 x16 interface, same OAM Module form factor, and both lack display outputs and graphics API support. The recorded data shows a generational shift in which the MI355X trades transistor density and power efficiency for higher absolute compute, more memory, and faster bandwidth.