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AMD Steps Up to 4K Gaming

December 1, 2020

Author: Linley Gwennap

After grabbing the performance lead in CPUs, AMD is on a mission to top the GPU charts as well. Its newest Radeon graphics cards employ a chip aptly called Big Navi, which doubles both performance and die size over last year’s Navi design. These increases allow AMD for the first time to target gamers that use 4K-resolution displays. The new Radeon RX 6800, 6800XT, and 6900XT cards are all shipping or due to ship shortly.

The Big Navi design is evolutionary in some ways but has a radical new twist. The compute-performance increase mainly comes from doubling the number of shader cores and compute units (CUs), along with a clock-frequency boost. But to satisfy the much greater memory bandwidth required to feed so many compute units, AMD added a huge level-three (L3) cache that it dubs (with slight exaggeration) the Infinity Cache. This 128MB structure not only provides the necessary bandwidth but also greatly reduces power compared with accessing the external GDDR6 DRAM. That addition, along with smaller changes, allows the new design to double Navi’s performance while consuming only 33% more power (TDP), despite using the same 7nm process.

Big Navi is also the first AMD GPU to implement hardware ray tracing, matching Nvidia’s GPUs. The new ray-tracing unit is 10x faster than the previous one, which implemented the function using standard CU instructions. The L3 cache is important for ray tracing as well: it’s big enough to hold most of the ray-tracing information on the chip, improving performance relative to accessing DRAM.

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