AMD Radeon RX 6900 XT vs NVIDIA GeForce RTX 4080 Mobile Comparison

Where Each One Wins

The recorded benchmark data splits these two GPUs into clearly different use-case profiles. The AMD Radeon RX 6900 XT wins 8 of the 9 shared head-to-head tests, while the NVIDIA GeForce RTX 4080 Mobile manages only a single victory. That one win is in the legacy DirectX 9 test, where the NVIDIA part posts a score of 286 against 268 for the AMD card, a 6.3% advantage. Every other category favors the desktop AMD flagship.

The RX 6900 XT dominates in compute-oriented workloads. Its largest margin comes in Passmark GPU Compute, where it scores 14,547 against 11,191 for the RTX 4080 Mobile, a 30% gap. That is the single biggest win in the entire head-to-head set. The AMD card also leads in DirectX 12 by 17.7%, DirectX 11 by 14.3%, and OpenCL by 17.6%, showing consistent strength across modern API paths.

For pure rasterization, the AMD card leads Passmark G3D by 7.2% (26,732 versus 24,926). The margin narrows in Vulkan where the RX 6900 XT scores 148,525 versus 145,807, just 1.9% ahead. The 2D workload also goes AMD's way, with a 13.6% advantage (1,055 versus 929). The RTX 4080 Mobile's only other close result is DirectX 10, where it trails by 6.4% (167 versus 157).

When considering the percentile rankings, the RX 6900 XT sits at the 86th percentile among all GPUs in the database, while the RTX 4080 Mobile records the 81st percentile. The average benchmark score also favors AMD: 50,951 versus 38,135, a difference of roughly 33.6% but that figure is derived from the published averages, not a direct head-to-head calculation.

Architecture Differences

The two GPUs come from fundamentally different design philosophies. The AMD RX 6900 XT is based on the Navi 21 chip, using the RDNA 2.0 architecture, fabricated on a 7 nm process at TSMC. It packs 26,800 million transistors on a 520 mm² die, giving a transistor density of 51.5 million per mm². The NVIDIA RTX 4080 Mobile uses the AD104 chip, built on Ada Lovelace architecture, on a 5 nm process, also at TSMC. It contains 35,800 million transistors on a 294 mm² die, achieving a much higher density of 121.8 million per mm².

The GPU layout differs substantially. The AMD card has 5,120 shading units, 320 TMUs, and 128 ROPs, with 80 RT cores and no tensor cores. The NVIDIA part has 7,424 shading units, 232 TMUs, 80 ROPs, 58 RT cores, and 232 tensor cores. The higher shading unit count gives NVIDIA the theoretical FP32 peak of 24.72 TFLOPS versus AMD's 23.04 TFLOPS, but the AMD card reaches 46.08 TFLOPS FP16 (2:1 ratio) while the NVIDIA card does 24.72 TFLOPS FP16 (1:1 ratio).

Memory design differs significantly. The RX 6900 XT uses 16 GB of GDDR6 on a 256-bit bus, delivering 512.0 GB/s bandwidth. The RTX 4080 Mobile has 12 GB of GDDR6 on a 192-bit bus, with 432.0 GB/s bandwidth. The AMD card also has higher pixel rate (288.0 GPixel/s versus 133.2 GPixel/s) and texture rate (720.0 GTexel/s versus 386.3 GTexel/s).

The power envelopes set them farther apart. The RX 6900 XT is a 300 W desktop card, triple-slot, requiring 2x 8-pin power connectors and a 700 W PSU. The RTX 4080 Mobile is an integrated graphics processor with a 110 W TDP, no external power connectors, and its display outputs are listed as portable device dependent. The AMD card is end-of-life, released in 2020, while the NVIDIA part is active, released in 2023.

Head-to-Head Benchmarks

The largest margin is in PassMark GPU Compute, where AMD scores 14,547 versus NVIDIA's 11,191, a 30% advantage. This result strongly favors the AMD architecture for general compute workloads. The second-largest win is in PassMark DirectX 12, where AMD scores 113 versus 96, a 17.7% margin. The DirectX 11 test also goes to AMD by 14.3% (279 versus 244).

OpenCL results show AMD ahead by 17.6% (187,673 versus 159,575). The DirectX 10 test is close, AMD wins by 6.4% (167 versus 157). The 2D test shows a 13.6% AMD advantage (1,055 versus 929). The 3D test (G3D) has AMD ahead by 7.2% (26,732 versus 24,926). The Vulkan test is the closest, with AMD winning by 1.9% (148,525 versus 145,807).

The single NVIDIA win is PassMark DirectX 9, where it scores 286 versus AMD's 268, a margin of 6.3%. This suggests the older DirectX 9 path is a relative weakness for the RDNA 2 architecture, though the absolute difference is small in percentage terms and the test is legacy.

Looking at the overall average scores, the RX 6900 XT's nearest rivals include the NVIDIA CMP 50HX at 51,790 average score (1.6% below AMD), the AMD Radeon RX Vega 64 at 50,001 (1.9% below), the NVIDIA GeForce RTX 5070 Ti at 49,957 (2% below), and the Intel Arc A550M at 49,737 (2.4% below). The RTX 4080 Mobile sits near the MX570 at 38,299 average score (0.4% below), the RTX 5080 Mobile at 38,349 (0.6% below), and the RTX 4070 at 37,648 (1.3% below).

FAQ

Q: Which card wins in DirectX 12 benchmarks?

A: The AMD Radeon RX 6900 XT wins the PassMark DirectX 12 test with a score of 113 versus 96 for the RTX 4080 Mobile, a 17.7% advantage.

Q: Is the RTX 4080 Mobile ever ahead of the RX 6900 XT?

A: Yes, in only one test: PassMark DirectX 9, where the NVIDIA card scores 286 versus AMD's 268, a 6.3% lead.

Q: What is the largest performance gap between the two?

A: The largest gap is in PassMark GPU Compute, where the RX 6900 XT scores 14,547 versus 11,191 for the RTX 4080 Mobile, a 30% difference.

Q: How do the memory bandwidths compare?

A: The RX 6900 XT has a 256-bit bus with 512.0 GB/s bandwidth, while the RTX 4080 Mobile has a 192-bit bus with 432.0 GB/s bandwidth.

Q: Which card has higher peak FP32 performance?

A: The RTX 4080 Mobile has a higher FP32 peak at 24.72 TFLOPS, while the RX 6900 XT reaches 23.04 TFLOPS.

Q: How do their percentile ranks compare?

A: The RX 6900 XT is at the 86th percentile of all GPUs, while the RTX 4080 Mobile is at the 81st percentile.

Specification Differences

The two GPUs differ in nearly every measurable specification. The AMD RX 6900 XT uses a 7nm process with 26,800 million transistors on a 520 mm² die. The NVIDIA RTX 4080 Mobile uses a 5nm process with 35,800 million transistors on a 294 mm² die. The NVIDIA transistor density is 121.8M / mm² compared to AMD's 51.5M / mm².

Memory capacity differs: 16 GB for AMD (GDDR6, 256-bit, 512.0 GB/s) versus 12 GB for NVIDIA (GDDR6, 192-bit, 432.0 GB/s). The base clock for AMD is 1825 MHz with a boost of 2250 MHz, while NVIDIA's base is 1290 MHz with a boost of 1665 MHz. AMD also has a game clock of 2015 MHz; NVIDIA does not list one.

Shading units favor NVIDIA (7,424 versus 5,120), but TMUs favor AMD (320 versus 232). ROPs also favor AMD (128 versus 80). AMD has 80 RT cores; NVIDIA has 58, but NVIDIA adds 232 tensor cores. The FP32 peak is NVIDIA (24.72 vs 23.04 TFLOPS). The FP16 peak is AMD (46.08 TFLOPS at 2:1 ratio) versus NVIDIA (24.72 at 1:1 ratio).

The power draw is 300 W for AMD versus 110 W for NVIDIA. The AMD card is triple-slot with 2x 8-pin power, while NVIDIA is IGP with no power connectors. The AMD card has specific display outputs (1x HDMI 2.1, 2x DisplayPort 1.4a, 1x USB Type-C), while NVIDIA's are portable device dependent. The AMD card has a launch MSRP of 999 USD; the NVIDIA card has no recorded launch MSRP.

The Verdict

The recorded data points to a clear performance hierarchy. The AMD Radeon RX 6900 XT leads in 8 of 9 shared tests, with a 30% peak margin in compute and consistent advantages across all modern APIs (DX11, DX12, OpenCL, Vulkan). It also holds a 7.2% lead in the mainstream 3D benchmark. The RTX 4080 Mobile wins only in the legacy DirectX 9 path.

The RTX 4080 Mobile offers more shading units and higher FP32 peak, but that does not translate into benchmark wins. Its power envelope is dramatically lower at 110 W, making it a mobile solution, while the RX 6900 XT at 300 W is a desktop part. The RX 6900 XT also has more memory (16 GB) and more bandwidth (512 GB/s) than the RTX 4080 Mobile.

The RTX 4080 Mobile's only advantage beyond the single DirectX 9 win is its tensor core count (232 versus none) and its 5nm process efficiency. The average benchmark scores show the RX 6900 XT at 50,951 versus 38,135 for the RTX 4080 Mobile. The RX 6900 XT ranks at the 86th percentile, the RTX 4080 Mobile at the 81st. For anyone who needs compute performance, the AMD card is the stronger choice. For a portable, power-sipping device, the RTX 4080 Mobile has its place.