AMD Radeon R9 M390X vs AMD Radeon RX 7900 XTX Comparison

The AMD Radeon R9 M390X and AMD Radeon RX 7900 XTX represent two vastly different eras of GPU design, separated by seven years of architectural evolution. The R9 M390X is an end-of-life mobile graphics solution built for laptops in 2015, while the RX 7900 XTX is a flagship desktop card from 2022 that has also reached end-of-life status. Benchmark data shows the newer card dominates the single shared test, but the comparison reveals fundamental shifts in GPU technology, from manufacturing processes to memory subsystems and compute capabilities.

Architecture Differences

The R9 M390X is built on the GCN 3.0 architecture, codenamed Amethyst, and belongs to the Gem System (R9 M300) generation. It uses a 28 nm process from TSMC, housing 5,000 million transistors on a 366 mm² die for a transistor density of 13.7M per mm². The RX 7900 XTX, by contrast, employs the RDNA 3.0 architecture on TSMC's 5 nm node, packing 57,700 million transistors into a 529 mm² die, achieving a density of 109.1M per mm². This represents a nearly 8-fold increase in transistor density.

The R9 M390X features 2,048 shading units, 128 texture mapping units, and 32 raster operations pipelines. The RX 7900 XTX scales this dramatically to 6,144 shading units, 384 TMUs, and 192 ROPs. The newer card also introduces 96 dedicated ray tracing cores, a feature entirely absent from the older GCN design. The R9 M390X offers FP32 performance of 2.961 TFLOPS and FP16 at a 1:1 ratio, while the RX 7900 XTX delivers 61.39 TFLOPS FP32 and 122.8 TFLOPS FP16 at a 2:1 ratio.

Memory architecture differs fundamentally between the two. The R9 M390X uses 4 GB of GDDR5 on a 256-bit bus, yielding 160.0 GB/s of bandwidth. The RX 7900 XTX ships with 24 GB of GDDR6 across a 384-bit interface, providing 960.0 GB/s — six times the bandwidth. Clock speeds tell a similar story: the R9 M390X memory runs at 1250 MHz (5 Gbps effective), while the RX 7900 XTX memory operates at 2500 MHz (20 Gbps effective).

API support has also evolved. The R9 M390X supports DirectX 12 (12_0), OpenGL 4.6, and Vulkan 1.2.170. The RX 7900 XTX supports DirectX 12 Ultimate (12_2), OpenGL 4.6, and Vulkan 1.4. The newer card also features PCIe 4.0 x16 connectivity versus PCIe 3.0 x16 on the older part.

Where Each One Wins

The R9 M390X wins in the portability and power efficiency domain. With a TDP of 75 W and a compact MXM Module form factor, it was designed for notebooks where space and thermal limits are paramount. It requires no external power connectors and uses a PCIe 3.0 x16 interface. The RX 7900 XTX, at 355 W TDP, demands a dual-slot cooling solution, two 8-pin power connectors, and a suggested 750 W power supply. The R9 M390X is portable-device dependent for display outputs, meaning it adapts to whatever the laptop manufacturer provides.

The RX 7900 XTX wins in every performance metric. Its pixel rate of 479.6 GPixel/s dwarfs the R9 M390X's 23.14 GPixel/s. Texture rate reaches 959.2 GTexel/s versus 92.54 GTexel/s. The 7900 XTX also provides a full complement of desktop display outputs: 1x HDMI 2.1a, 2x DisplayPort 2.1, and 1x USB Type-C. Physical dimensions reflect the desktop orientation — 287 mm length, 110 mm height, and 51 mm width.

The R9 M390X holds an advantage in environmental flexibility. Its lower power draw allows deployment in laptops and compact systems where the 7900 XTX simply cannot fit. The 7900 XTX compensates with raw compute capability that enables 4K gaming, ray tracing workloads, and professional content creation tasks that would overwhelm the older mobile chip.

Head-to-Head Benchmarks

The single shared benchmark between these two GPUs is Geekbench Vulkan, and the results are lopsided. The R9 M390X scores 16,951, while the RX 7900 XTX achieves 85,612. This represents a delta of -80.2% for the older card, meaning the 7900 XTX is approximately five times faster in this compute-oriented test. The gap reflects not just the generational improvement in raw throughput but also the architectural efficiency gains from GCN 3.0 to RDNA 3.0.

Looking at broader benchmark data, the RX 7900 XTX demonstrates its strength across multiple test suites. In Passmark G3D, it scores 31,238, while GPU compute reaches 17,689. Geekbench OpenCL yields 50,465. The R9 M390X's average benchmark score is 20,662, whereas the 7900 XTX averages 19,410 across all its tested workloads. Interestingly, this aggregate figure places both cards in similar percentile territory — 66th percentile for the R9 M390X versus 64th for the RX 7900 XTX — but this is misleading due to different test sets.

The nearestRivals data provides context for each card's standing. The R9 M390X sits within 0.6% of the AMD Radeon RX 5600 XT (delta -0.2%), Intel Arc A750 (+0.4%), Intel Arc B570 (+0.5%), and NVIDIA GeForce RTX 3070 Mobile (+0.6%). The RX 7900 XTX's nearest rivals include the NVIDIA GeForce GTX 1060 3 GB (+0.4%), NVIDIA Quadro K5200 (-1%), AMD FirePro D300 (-1.2%), and NVIDIA TITAN Xp (+1.2%). This indicates that despite vastly different absolute performance levels, both cards cluster with their respective peer groups in the aggregate benchmark database.

FAQ

Q: Which GPU has better ray tracing performance?

A: The AMD Radeon RX 7900 XTX features 96 dedicated ray tracing cores, while the R9 M390X has no ray tracing hardware at all. This makes the 7900 XTX the only option for hardware-accelerated ray tracing workloads.

Q: What is the memory capacity difference between these cards?

A: The R9 M390X ships with 4 GB of GDDR5, while the RX 7900 XTX provides 24 GB of GDDR6. The newer card also offers a wider 384-bit bus versus 256-bit, resulting in 960.0 GB/s bandwidth compared to 160.0 GB/s.

Q: Can the R9 M390X run modern games?

A: The R9 M390X supports DirectX 12 (12_0) and Vulkan 1.2.170, so it can run modern titles at reduced settings. However, its 2.961 TFLOPS FP32 performance and 4 GB memory capacity are severely limited compared to contemporary GPUs.

Q: What power supply is recommended for the RX 7900 XTX?

A: The RX 7900 XTX has a TDP of 355 W, requires two 8-pin power connectors, and AMD suggests a 750 W power supply for the overall system.

Q: How does the transistor density compare?

A: The R9 M390X achieves 13.7 million transistors per mm² on a 28 nm process, while the RX 7900 XTX reaches 109.1 million per mm² on 5 nm. The newer card packs 57,700 million total transistors versus 5,000 million.

Q: Which card has better API support?

A: The RX 7900 XTX supports DirectX 12 Ultimate (12_2) and Vulkan 1.4, while the R9 M390X is limited to DirectX 12 (12_0) and Vulkan 1.2.170. Both support OpenGL 4.6.

Specification Differences

| Specification | AMD Radeon R9 M390X | AMD Radeon RX 7900 XTX |

|---|---|---|

| Architecture | GCN 3.0 | RDNA 3.0 |

| Process Node | 28 nm | 5 nm |

| Transistors | 5,000 million | 57,700 million |

| Die Size | 366 mm² | 529 mm² |

| Transistor Density | 13.7M / mm² | 109.1M / mm² |

| Memory Size | 4 GB | 24 GB |

| Memory Type | GDDR5 | GDDR6 |

| Memory Bus Width | 256 bit | 384 bit |

| Memory Bandwidth | 160.0 GB/s | 960.0 GB/s |

| Shading Units | 2048 | 6144 |

| TMUs | 128 | 384 |

| ROPs | 32 | 192 |

| RT Cores | None | 96 |

| FP32 Performance | 2.961 TFLOPS | 61.39 TFLOPS |

| FP16 Performance | 2.961 TFLOPS (1:1) | 122.8 TFLOPS (2:1) |

| Pixel Rate | 23.14 GPixel/s | 479.6 GPixel/s |

| Texture Rate | 92.54 GTexel/s | 959.2 GTexel/s |

| TDP | 75 W | 355 W |

| Slot Width | MXM Module | Dual-slot |

| Power Connectors | None | 2x 8-pin |

| Suggested PSU | None | 750 W |

| Bus Interface | PCIe 3.0 x16 | PCIe 4.0 x16 |

| DirectX Support | 12 (12_0) | 12 Ultimate (12_2) |

| Vulkan Support | 1.2.170 | 1.4 |

| Release Date | 2015-05-04 | 2022-11-02 |

The RX 7900 XTX carries a launch MSRP of 999 USD. Both cards are end-of-life products, with the R9 M390X succeeding the Solar System generation and preceding Polaris Mobile, while the RX 7900 XTX follows Navi II and precedes Navi IV. The R9 M390X's display outputs are portable device dependent, whereas the 7900 XTX provides 1x HDMI 2.1a, 2x DisplayPort 2.1, and 1x USB Type-C. The 7900 XTX measures 287 mm in length, 110 mm in height, and 51 mm in width, dimensions the MXM-format R9 M390X does not specify.