AMD Instinct MI455X vs AMD Radeon Instinct MI308X Comparison

Head-to-Head Benchmarks

The database records no executed benchmark runs for either the AMD Instinct MI455X or the AMD Radeon Instinct MI308X. Both parts show an average benchmark score of 0 and a percentile ranking of 50 against all GPUs in the database. Consequently, there are no head-to-head results, no win counts, and no rival comparisons to reference. The analysis below must therefore rely entirely on the recorded architectural and specification data, which provides a clear basis for projecting relative performance in compute workloads.

The FP32 throughput figures offer the most direct comparison. The MI455X delivers 157.3 TFLOPS of FP32 compute, while the MI308X delivers 81.72 TFLOPS. This means the MI455X provides roughly 92.5% higher FP32 throughput than the MI308X, a substantial advantage for workloads that rely on single-precision floating-point math. In FP16, the picture changes dramatically. The MI455X reports 157.3 TFLOPS at a 1:1 ratio to FP32, while the MI308X reports 653.7 TFLOPS at an 8:1 ratio. The MI308X therefore delivers over four times the FP16 throughput of the MI455X, but only when the workload can exploit the 8:1 packed math path. For FP16 tasks that require full precision per operation, the MI455X maintains its 1:1 rate, whereas the MI308X would drop to its FP32-equivalent rate of 81.72 TFLOPS.

Memory bandwidth also favors the newer part. The MI455X boasts 23.3 TB/s of bandwidth across a 24576-bit bus with HBM4 memory, while the MI308X provides 10.3 TB/s across an 8192-bit bus with HBM3. The MI455X more than doubles the bandwidth, which directly benefits large matrix operations, training loops, and inference batches that are memory-bound. Texture rate is the one metric where the MI308X leads: 2,553.6 GTexel/s versus 2,457.6 GTexel/s for the MI455X. This is a narrow 3.9% margin, and given that both cards are accelerator modules with no display outputs, texture rate is unlikely to be the deciding factor in any real deployment.

Architecture Differences

The MI455X uses the CDNA 5.0 architecture on TSMC's 2 nm process node, while the MI308X uses CDNA 3.0 on a 5 nm node. The process shrink is significant: the MI455X packs 320,000 million transistors into a 2990 mm² die, yielding a transistor density of 107.0M per mm². The MI308X contains 153,000 million transistors on a 1017 mm² die, with a higher density of 150.4M per mm². The MI455X has more than double the transistor count and nearly triple the die area, but the older MI308X is actually denser, meaning the MI455X uses its larger die more for raw compute resources than for packing efficiency.

The MI455X carries 32,768 shading units and 1,024 texture mapping units. The MI308X has 19,456 shading units and 1,216 TMUs. Despite having fewer shading units, the MI308X has more TMUs, which explains its slightly higher texture rate. Neither part has ROPs, as both are compute accelerators with zero pixel output. Ray tracing cores and tensor cores are not listed for either product, so no comparison is possible there.

Memory architecture differs substantially. The MI455X uses 432 GB of HBM4 on a 24576-bit interface, while the MI308X uses 192 GB of HBM3 on an 8192-bit bus. The MI455X offers 2.25 times the capacity and 2.26 times the bandwidth. Effective memory clock also differs: 7.6 Gbps for the MI455X versus 10.1 Gbps for the MI308X. The MI308X runs its memory faster per pin, but the MI455X compensates with a much wider bus.

The MI455X is built on the "MI450 256CU" chip, while the MI308X uses "Aqua Vanjaram". The MI455X belongs to the Instinct (MIx) generation with a predecessor of Radeon Instinct. The MI308X belongs to the Radeon Instinct (MIx) generation with a predecessor of FirePro Data Center. Both are accelerator modules: the MI455X is an EAM Module, and the MI308X is an OAM Module. Neither has display outputs, and both use no power connectors, relying instead on the module socket for power delivery.

FAQ

Q: Which GPU has higher FP32 compute performance?

A: The MI455X delivers 157.3 TFLOPS of FP32, which is 92.5% higher than the MI308X's 81.72 TFLOPS. For single-precision compute tasks, the MI455X has a clear advantage.

Q: Does the MI308X have any compute advantage over the MI455X?

A: Yes, in FP16 throughput. The MI308X reaches 653.7 TFLOPS at an 8:1 ratio, while the MI455X provides 157.3 TFLOPS at a 1:1 ratio. The MI308X also has a slightly higher texture rate at 2,553.6 GTexel/s versus 2,457.6 GTexel/s.

Q: How do the memory systems compare?

A: The MI455X has 432 GB of HBM4 with a 24576-bit bus and 23.3 TB/s bandwidth. The MI308X has 192 GB of HBM3 with an 8192-bit bus and 10.3 TB/s bandwidth. The MI455X offers more than double the capacity and bandwidth.

Q: What are the power requirements for each module?

A: The MI455X has a TDP of 2300 W and a suggested PSU of 2700 W. The MI308X has a TDP of 750 W and a suggested PSU of 1150 W. The MI455X requires substantially more power.

Q: Which GPU uses a newer manufacturing process?

A: The MI455X uses TSMC's 2 nm process, while the MI308X uses TSMC's 5 nm process. The MI455X is built on the newer CDNA 5.0 architecture, whereas the MI308X uses CDNA 3.0.

Q: Do either of these cards support display output?

A: No. Both the MI455X and the MI308X have no display outputs. They are compute accelerators with no pixel rate (0 MPixel/s) and no ROPs.

Specification Differences

The two accelerators differ in nearly every major specification category. The MI455X uses the MI450 256CU chip with CDNA 5.0 architecture, while the MI308X uses the Aqua Vanjaram chip with CDNA 3.0. Process nodes are 2 nm for the MI455X and 5 nm for the MI308X, both from TSMC. The MI455X contains 320,000 million transistors on a 2990 mm² die, versus 153,000 million transistors on a 1017 mm² die for the MI308X. Transistor density is 107.0M per mm² for the MI455X and 150.4M per mm² for the MI308X.

Clock speeds: both have a 1000 MHz base clock. The MI455X boosts to 2400 MHz, while the MI308X boosts to 2100 MHz. Memory clocks are 1900 MHz (7.6 Gbps effective) for the MI455X and 2525 MHz (10.1 Gbps effective) for the MI308X. The MI455X has 32,768 shading units and 1,024 TMUs; the MI308X has 19,456 shading units and 1,216 TMUs. Both have 0 ROPs.

Memory: 432 GB of HBM4 on a 24576-bit interface with 23.3 TB/s bandwidth for the MI455X, versus 192 GB of HBM3 on an 8192-bit interface with 10.3 TB/s for the MI308X. FP32 rates are 157.3 TFLOPS and 81.72 TFLOPS respectively. FP16 rates are 157.3 TFLOPS (1:1) for the MI455X and 653.7 TFLOPS (8:1) for the MI308X. Texture rates are 2,457.6 GTexel/s and 2,553.6 GTexel/s.

Power and form factor: the MI455X has a 2300 W TDP with a 2700 W suggested PSU, and uses an EAM Module slot. The MI308X has a 750 W TDP with a 1150 W suggested PSU, and uses an OAM Module slot. Neither uses power connectors. Bus interfaces differ: PCIe 6.0 x16 for the MI455X, PCIe 5.0 x16 for the MI308X. The MI455X has no API support listed for DirectX, OpenGL, or Vulkan; the MI308X has null entries for all three. Release dates are 2026-07-22 for the MI455X and 2023-12-05 for the MI308X.

The Verdict

The recorded data shows two accelerators with opposite strengths. The MI455X wins decisively on FP32 compute, memory capacity, memory bandwidth, transistor count, die size, boost clock, and bus interface generation. The MI308X wins on FP16 throughput, texture rate, transistor density, memory clock speed, TDP efficiency, and release timing. Neither part has display outputs, ROPs, or benchmark scores in the database, so any deployment decision must rest on workload characteristics.

For workloads dominated by FP32 math or by memory-bound operations, the MI455X is the stronger part. Its 157.3 TFLOPS FP32 and 23.3 TB/s bandwidth give it a commanding edge over the MI308X in these areas. The 432 GB memory capacity also allows it to hold far larger models or datasets in memory without spilling to host storage. The 2400 MHz boost clock versus 2100 MHz further reinforces the MI455X's compute advantage.

For workloads that can use packed FP16 math, the MI308X is the better choice. Its 653.7 TFLOPS at 8:1 ratio is more than four times the MI455X's 157.3 TFLOPS at 1:1. The MI308X also draws 1550 W less power, which matters in dense server racks with limited power delivery. Its 750 W TDP and 1150 W suggested PSU make it far easier to deploy in existing infrastructure.

Where Each One Wins

The MI455X wins in FP32 compute, where it offers 157.3 TFLOPS versus 81.72 TFLOPS. It also wins in memory capacity (432 GB versus 192 GB), memory bandwidth (23.3 TB/s versus 10.3 TB/s), and memory bus width (24576-bit versus 8192-bit). The MI455X has a higher boost clock (2400 MHz versus 2100 MHz), more shading units (32,768 versus 19,456), more transistors (320,000 million versus 153,000 million), a larger die (2990 mm² versus 1017 mm²), a newer process node (2 nm versus 5 nm), newer architecture (CDNA 5.0 versus CDNA 3.0), newer memory type (HBM4 versus HBM3), and a newer bus interface (PCIe 6.0 x16 versus PCIe 5.0 x16). It also uses a more recent generation per the release date of 2026-07-22.

The MI308X wins in FP16 throughput, delivering 653.7 TFLOPS at an 8:1 ratio compared to 157.3 TFLOPS at 1:1 for the MI455X. It has a higher texture rate (2,553.6 GTexel/s versus 2,457.6 GTexel/s), more TMUs (1,216 versus 1,024), higher transistor density (150.4M per mm² versus 107.0M per mm²), and a faster effective memory clock (10.1 Gbps versus 7.6 Gbps). It also wins in power efficiency, with a 750 W TDP and 1150 W suggested PSU compared to 2300 W and 2700 W for the MI455X. The MI308X has an earlier release date of 2023-12-05, meaning it has been available longer.