AMD Instinct MI325X vs AMD Instinct MI355X Comparison

Head-to-Head Benchmarks

The database currently records no completed benchmark runs for either the AMD Instinct MI325X or the AMD Instinct MI355X. Both parts have an average benchmark score of 0 and hold the 50th percentile position among all GPUs in the database, which is a neutral placeholder pending actual workload results. With no head-to-head benchmark entries, no wins are awarded to either accelerator, and there is no performance delta percentage to report between the two.

The absence of measured data means that direct comparisons of compute throughput, memory bandwidth scaling, or application-level performance cannot be quantified from the recorded information. The MI325X and MI355X both sit at the 50th percentile, which in the database's ranking scheme indicates that neither has yet demonstrated a measurable advantage over the other in real-world tests. Benchmark results will be required to populate the head-to-head table before any definitive performance verdict can be drawn.

FAQ

Q: What is the memory capacity difference between the MI325X and MI355X?

A: The MI325X ships with 256 GB of HBM3e memory, while the MI355X carries 288 GB of the same memory type. That is a 32 GB increase in capacity for the newer part.

Q: How does memory bandwidth compare between the two accelerators?

A: The MI325X delivers 6.14 TB/s of bandwidth, and the MI355X reaches 8.19 TB/s. Both use an 8192-bit memory bus, but the MI355X runs its HBM3e at a higher effective data rate.

Q: Which accelerator has a higher boost clock?

A: The MI355X boosts to 2400 MHz, whereas the MI325X boosts to 2100 MHz. The base clock is identical at 1000 MHz for both parts.

Q: Are the FP32 and FP16 compute figures different between the two?

A: Yes. The MI325X provides 81.72 TFLOPS for both FP32 and FP16 (1:1 ratio). The MI355X provides 78.64 TFLOPS for both FP32 and FP16 (1:1 ratio). The MI325X holds a small compute lead despite the older architecture.

Q: What is the transistor count and die size for each chip?

A: The MI325X uses the Aqua Vanjaram chip with 153,000 million transistors on a 1017 mm² die. The MI355X uses the MI350 256CU chip with 185,000 million transistors on a 2380 mm² die.

Q: Do both accelerators support the same PCIe interface?

A: Yes, both use PCIe 5.0 x16 as their bus interface. Neither has any display outputs, and both are OAM Modules with no power connectors on the card itself.

Architecture Differences

The MI325X is built on CDNA 3.0 architecture, while the MI355X moves to CDNA 4.0. This architectural generation change brings the MI355X to a 3 nm process node at TSMC, compared to the 5 nm node used for the MI325X. The chip design differs substantially: the MI325X uses the Aqua Vanjaram die, and the MI355X uses the MI350 256CU die.

Transistor density tells an interesting story. The MI325X crams 150.4 million transistors per square millimeter into its 1017 mm² die. The MI355X spreads 185,000 million transistors across a much larger 2380 mm² die, yielding a lower density of 77.7 million transistors per square millimeter. The larger die and higher transistor count for the MI355X indicate a fundamentally different physical layout despite the refined process node.

Shader engine configuration also differs. The MI325X has 19,456 shading units, 1,216 texture mapping units, and no raster output units. The MI355X scales down to 16,384 shading units and 1,024 texture mapping units, also with zero ROPs. The pixel rate for both is recorded as 0 MPixel/s, consistent with their compute-focused design that lacks traditional rasterization hardware.

Texture rate favors the MI325X at 2,553.6 GTexel/s versus 2,457.6 GTexel/s for the MI355X. This is a direct consequence of the higher shading unit count in the older part, even though the newer part has a higher boost clock.

The MI355X has physical dimensions recorded in the database: 102 mm in length and 165 mm in width. The MI325X has no recorded dimensions. Both are OAM Modules, which means they are designed for system-level integration rather than standard expansion slots.

The FP32 and FP16 compute figures are identical within each part, indicating a 1:1 ratio that is typical for CDNA accelerators focused on matrix math and AI workloads. The MI325X achieves 81.72 TFLOPS in both precisions, while the MI355X achieves 78.64 TFLOPS in both precisions. Despite the architecture upgrade, the MI325X retains a compute throughput advantage of roughly 3.08 TFLOPS.

Specification Differences

The clock speeds differ in the boost frequency. The MI325X has a 1000 MHz base and 2100 MHz boost. The MI355X has the same 1000 MHz base but a 2400 MHz boost, which is a 300 MHz higher ceiling.

Memory specifications diverge on capacity and bandwidth. The MI325X offers 256 GB of HBM3e with 6.14 TB/s bandwidth. The MI355X offers 288 GB of HBM3e with 8.19 TB/s bandwidth. The memory clock is 1500 MHz with 6 Gbps effective data rate for the MI325X, and 2000 MHz with 8 Gbps effective for the MI355X. The bus width is identical at 8192 bits, so the bandwidth gain comes entirely from the faster memory clock.

Compute resources differ in count. The MI325X has 19,456 shading units and 1,216 TMUs. The MI355X has 16,384 shading units and 1,024 TMUs. The texture rate is 2,553.6 GTexel/s for the MI325X and 2,457.6 GTexel/s for the MI355X. Both parts report 0 MPixel/s pixel rate and no RT or tensor core counts in the database.

Power requirements are higher for the newer part. The MI325X has a TDP of 1000 W and a suggested PSU rating of 1400 W. The MI355X has a TDP of 1400 W and a suggested PSU rating of 1800 W. Both use OAM Module slot width, have no power connectors, and support PCIe 5.0 x16. Neither has display outputs, and neither supports DirectX, OpenGL, or Vulkan APIs.

The die characteristics are markedly different. The MI325X uses a 5 nm process with 153,000 million transistors on a 1017 mm² die. The MI355X uses a 3 nm process with 185,000 million transistors on a 2380 mm² die. The transistor density drops from 150.4M per mm² to 77.7M per mm² despite the smaller process node.

Release timing also differs. The MI325X was released on October 9, 2024, and the MI355X followed on June 11, 2025. Both are in the Instinct (MIx) generation and list Radeon Instinct as their predecessor. Neither has a successor recorded in the database, and neither has a launch MSRP listed.

The Verdict

The recorded data favors the MI325X in raw compute throughput. Its 81.72 TFLOPS FP32 and FP16 figures exceed the MI355X's 78.64 TFLOPS in both precisions. The MI325X also has more shading units (19,456 versus 16,384), more TMUs (1,216 versus 1,024), and a higher texture rate (2,553.6 GTexel/s versus 2,457.6 GTexel/s). For workloads that scale with shader count and texture throughput, the MI325X holds the edge based on specifications.

The MI355X wins on memory and power efficiency per unit of bandwidth. It offers 288 GB of HBM3e versus 256 GB, and its 8.19 TB/s bandwidth is substantially higher than the 6.14 TB/s of the MI325X. The 2400 MHz boost clock is also 300 MHz higher. However, this comes at a cost of 400 W additional TDP, raising the total from 1000 W to 1400 W, and the suggested PSU requirement jumps from 1400 W to 1800 W.

The MI355X uses a 3 nm process with 185,000 million transistors, while the MI325X uses a 5 nm process with 153,000 million transistors. The newer part packs more transistors onto a larger die, but the MI325X achieves much higher transistor density. The architecture shift from CDNA 3.0 to CDNA 4.0 does not translate into higher compute numbers in the database; the MI325X remains ahead in FP32 and FP16 throughput.

For memory-bound workloads such as large language model inference or training with massive batch sizes, the MI355X is the stronger choice due to its 288 GB capacity and 8.19 TB/s bandwidth. For compute-bound workloads where raw TFLOPS matter more than memory capacity, the MI325X delivers greater throughput at a lower power draw.

Both parts have no display outputs, no API support for graphics, and are OAM Modules requiring external power delivery through the system. The MI355X has recorded physical dimensions of 102 mm by 165 mm, while the MI325X has none in the database.

The absence of benchmark data means that real-world performance differences cannot be confirmed. The database shows both at the 50th percentile with zero average benchmark scores. Until workloads are run and recorded, the specification comparison is the only basis for selection. The MI325X suits compute-dense environments with a 1400 W PSU budget, and the MI355X suits memory-hungry deployments that can accommodate an 1800 W PSU and the larger die.