AMD Instinct MI455X vs AMD Radeon RX 7800M Comparison

Head-to-Head Benchmarks

The database contains no overlapping benchmark records for the AMD Instinct MI455X and the AMD Radeon RX 7800M. The MI455X lists zero benchmark entries, while the RX 7800M carries ten recorded tests. This absence of shared test data means a direct score-by-score comparison is impossible from the recorded measurements. What the data does provide is a clear asymmetry: one card has a substantial body of performance evidence, the other has none.

The RX 7800M's recorded scores cluster around compute and graphics workloads. Its 3DMark Steel Nomad DX12 result stands at 2994. Geekbench OpenCL returns 120778, and Geekbench Vulkan returns 126668. Passmark tests show a G3D score of 17613, a GPU compute score of 9342, and older API scores ranging from 89 in DirectX 12 to 99 in DirectX 10, with DirectX 11 at 176 and DirectX 9 at 174. The 2D score is 892. These figures place the RX 7800M at the 73rd percentile among all GPUs in the database, with an average benchmark score of 27883.

The MI455X, by contrast, holds a 50th percentile position with an average benchmark score of zero. The percentile value indicates where the card sits relative to the database population, but the zero score reflects the absence of any recorded test results. Without benchmark entries, the MI455X cannot be positioned against the RX 7800M in any workload category using the available data.

The nearest rivals for the RX 7800M provide additional context. The AMD Radeon Pro Vega 20 scores 27839, a delta of 0.2 percent relative to the RX 7800M. The AMD Radeon Pro W5500X scores 27973, a delta of -0.3 percent. The NVIDIA GeForce GTX 980 Ti scores 28020, a delta of -0.5 percent. The AMD FirePro S7150 scores 28117, a delta of -0.8 percent. These deltas show the RX 7800M sitting within a narrow band of comparable cards, all within roughly one percent of each other. The MI455X has no such rival list in the database, further limiting any comparative analysis.

Where Each One Wins

The RX 7800M wins in every category where data exists, simply because it is the only card with recorded results. Its Passmark G3D score of 17613 indicates strong rasterization performance for its class, while the GPU compute score of 9342 shows a separate, moderately capable compute profile. The Geekbench Vulkan score of 126668 slightly exceeds the OpenCL score of 120778, a 4.9 percent gap that suggests Vulkan API efficiency is marginally better on this part.

The MI455X cannot claim any recorded win because it has no benchmark entries. Its specification sheet, however, hints at capabilities the RX 7800M does not approach. The MI455X carries 32768 shading units against the RX 7800M's 3840, an 8.5 times difference. Texture units number 1024 versus 240, a 4.3 times gap. The MI455X lists no ROPs and a pixel rate of 0 MPixel/s, while the RX 7800M has 96 ROPs and a pixel rate of 224.2 GPixel/s. These raw differences suggest the MI455X is designed for compute-heavy workloads where rasterization throughput matters less, while the RX 7800M handles traditional graphics output.

The FP32 figures reinforce this split. The MI455X delivers 157.3 TFLOPS, while the RX 7800M delivers 35.87 TFLOPS. The MI455X leads by 4.4 times in raw floating-point throughput. Texture rate tells a similar story: 2457.6 GTexel/s versus 560.4 GTexel/s, a 4.4 times advantage for the MI455X. These are specification-derived wins, not benchmark wins, but they point to distinct use cases.

Architecture Differences

The two cards share a manufacturer but diverge at nearly every architectural level. The MI455X uses the MI450 256CU chip built on CDNA 5.0 architecture, fabricated at TSMC on a 2 nm process. The RX 7800M uses the Navi 32 chip built on RDNA 3.0 architecture, also from TSMC but on a 5 nm process. The process node difference is direct: 2 nm versus 5 nm, giving the MI455X a density advantage that its transistor count reflects.

Transistor counts show the scale gap. The MI455X packs 320,000 million transistors on a die size of 2990 mm², yielding a density of 107.0 million transistors per square millimeter. The RX 7800M has 28,100 million transistors on a 346 mm² die, a density of 81.2 million per square millimeter. The MI455X die is 8.6 times larger by area and holds 11.4 times more transistors.

Memory architecture differs fundamentally. The MI455X uses 432 GB of HBM4 on a 24576-bit bus, achieving 23.3 TB/s of bandwidth. The RX 7800M uses 12 GB of GDDR6 on a 192-bit bus, achieving 432.0 GB/s. The bandwidth gap is 53.9 times in favor of the MI455X. Memory clock speeds also differ: the MI455X runs at 1900 MHz with 7.6 Gbps effective, while the RX 7800M runs at 2250 MHz with 18 Gbps effective. The RX 7800M's memory clock is higher, but its narrow bus and smaller total capacity cannot compensate for the MI455X's massive HBM4 implementation.

Compute features reveal another split. The MI455X lists no RT cores and no tensor cores, while the RX 7800M includes 60 RT cores. The MI455X's CDNA 5.0 design targets general compute, evidenced by its 1:1 FP16 to FP32 ratio at 157.3 TFLOPS for both. The RX 7800M also shows a 1:1 ratio, but at 35.87 TFLOPS. The MI455X omits display outputs entirely, while the RX 7800M lists outputs as portable device dependent.

API support differs sharply. The MI455X reports no DirectX, OpenGL, or Vulkan support. The RX 7800M supports DirectX 12 Ultimate (12_2), OpenGL 4.6, and Vulkan 1.4. This makes the MI455X a compute-only accelerator, while the RX 7800M functions as a full graphics card.

Power and interface specifications continue the divergence. The MI455X has a TDP of 2300 W with a suggested PSU of 2700 W, while the RX 7800M has a TDP of 180 W and no suggested PSU listed. The MI455X uses a PCIe 6.0 x16 interface, the RX 7800M uses PCIe 4.0 x16. Slot widths differ: the MI455X is an EAM Module, the RX 7800M is an IGP.

FAQ

Q: Does the AMD Instinct MI455X have any recorded benchmark scores?

A: No. The database lists zero benchmark entries for the MI455X, and its average benchmark score is recorded as 0, placing it at the 50th percentile among all GPUs.

Q: What is the RX 7800M's strongest benchmark result?

A: Its Geekbench Vulkan score of 126668 is the highest recorded value, slightly ahead of its Geekbench OpenCL score of 120778. The Passmark G3D score of 17613 is the strongest Passmark result.

Q: How does the RX 7800M compare to its nearest rivals?

A: The RX 7800M sits within 0.8 percent of four rivals. It leads the AMD Radeon Pro Vega 20 by 0.2 percent, trails the AMD Radeon Pro W5500X by 0.3 percent, trails the NVIDIA GeForce GTX 980 Ti by 0.5 percent, and trails the AMD FirePro S7150 by 0.8 percent.

Q: Which card has higher memory bandwidth?

A: The MI455X records 23.3 TB/s from its 432 GB HBM4 pool on a 24576-bit bus, versus the RX 7800M's 432.0 GB/s from 12 GB GDDR6 on a 192-bit bus. The MI455X leads by a factor of 53.9.

Q: Can the MI455X run graphics APIs?

A: No. The database records DirectX, OpenGL, and Vulkan support as N/A for the MI455X. The RX 7800M supports DirectX 12 Ultimate, OpenGL 4.6, and Vulkan 1.4.

Q: What is the release timeline difference?

A: The RX 7800M has a release date of 2024-09-10, while the MI455X has a release date of 2026-07-22. The MI455X lists the Radeon Instinct as its predecessor, while the RX 7800M lists Polaris Mobile.

Specification Differences

The two cards differ in every major specification field. Process node: 2 nm for the MI455X, 5 nm for the RX 7800M. Transistors: 320,000 million versus 28,100 million. Die size: 2990 mm² versus 346 mm². Transistor density: 107.0M per mm² versus 81.2M per mm².

Clocks differ in base and memory speeds. The MI455X has a base clock of 1000 MHz and a boost of 2400 MHz. The RX 7800M has a base of 1295 MHz, a boost of 2335 MHz, and a game clock of 2145 MHz. Memory clocks: 1900 MHz with 7.6 Gbps effective for the MI455X, 2250 MHz with 18 Gbps effective for the RX 7800M.

Memory capacity: 432 GB versus 12 GB. Memory type: HBM4 versus GDDR6. Bus width: 24576 bit versus 192 bit. Bandwidth: 23.3 TB/s versus 432.0 GB/s.

Shading units: 32768 versus 3840. TMUs: 1024 versus 240. ROPs: 0 versus 96. RT cores: none recorded versus 60. Pixel rate: 0 MPixel/s versus 224.2 GPixel/s. Texture rate: 2457.6 GTexel/s versus 560.4 GTexel/s. FP32: 157.3 TFLOPS versus 35.87 TFLOPS. FP16: 157.3 TFLOPS versus 35.87 TFLOPS.

TDP: 2300 W versus 180 W. Slot width: EAM Module versus IGP. Suggested PSU: 2700 W versus none recorded. Bus interface: PCIe 6.0 x16 versus PCIe 4.0 x16. Display outputs: no outputs versus portable device dependent. APIs: N/A versus DirectX 12 Ultimate, OpenGL 4.6, Vulkan 1.4.

Release dates: 2026-07-22 versus 2024-09-10. Predecessors: Radeon Instinct versus Polaris Mobile. Production status: none recorded versus Active. The RX 7800M belongs to the Radeon RX 7000 series and Navi Mobile generation, while the MI455X belongs to the Instinct (MIx) generation with no series listed.

The Verdict

The data supports a clear division of roles. The RX 7800M is the only card with measured performance, showing strong results in both graphics and compute benchmarks. Its 73rd percentile ranking and average score of 27883 place it among capable mobile GPUs, with nearest rivals within one percent. The MI455X has no benchmark evidence, so its performance cannot be verified from the database.

Specifications favor the MI455X overwhelmingly in raw compute scale: 4.4 times the FP32 throughput, 53.9 times the memory bandwidth, 8.5 times the shading units, and 11.4 times the transistor count. But it lacks graphics outputs, API support, and any recorded test scores. The RX 7800M is a complete graphics solution with DirectX 12 Ultimate, Vulkan 1.4, and 60 RT cores, housed in a 180 W IGP package.

The release dates suggest the MI455X is a later part, appearing in 2026-07-22 versus the RX 7800M's 2024-09-10. The MI455X targets compute acceleration with its CDNA 5.0 architecture and 2300 W power envelope. The RX 7800M targets mobile graphics with its RDNA 3.0 architecture and 180 W TDP. Users needing a verified, working graphics card with recorded benchmark data should select the RX 7800M. Users requiring extreme compute throughput without graphics output would consider the MI455X, but its zero benchmark record means no performance validation exists in the database.