AMD Radeon RX 6800 series graphics cards have serious 4K cred

AMD is finally going after 4K gaming with its impressive top-end PC graphics cards, the Radeon RX 6800 and 6800 XT (and 6900 XT) after spending its time concentrating on value buyers. Its still-current RX 5700 XT was formerly the top of the line and designed for 1440p play, though I expect AMD will bring the rest of the Radeon cards up to date with the latest technologies. All the new cards incorporate the RDNA 2.0 architecture that's in the graphics processing units for the upcoming Xbox Series X and S and PS5 consoles and directly tackle the new Ampere-architecture GeForce RTX 3080 and 3070 recently launched by Nvidia. 

The RX 6800 and its higher-end sibling, the RX 6800 XT, fall between the Nvidia cards in performance and price -- at least by manufacturer price. The $579 (directly converted: £435, AU$790) RX 6800 falls between the $499 (£375, AU$680) RTX 3070 and the $699 (£525, AU$960) RTX 3080, while the $649 (£490, AU$890) RX 6800 XT competes almost directly with the RTX 3080. Actual prices can vary a lot, however, depending on stock and the "something extra" that third-party card makers throw into the mix, so they're frequently higher than AMD and Nvidia's explicit target. The new cards are available as of today.

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So far I'm impressed with the performance of both of the 6800 cards, but exactly how impressed will depend upon where the prices land when the market has settled. They both hit eminently playable 4K frame rates and that's before you start futzing with driver settings like overclocking and upscaling with FidelityFX, AMD's open-source image quality toolkit. When the cards are maxing out the graphics processing unit, the fans can get loud, but they never get too hot or unstable. (I never pushed them to the point where I'd expect them to, though.)  

Physically, the 6800 is narrower than the 6800 XT, and both are longer than Nvidia's RTX 3070 (but shorter than the RTX 3080). The three fans suck air in from the side and blow it out through the top and bottom; there's no venting out of the back as there is on the RTX cards. They use standard eight-pin power connectors and provide an HDMI, two DisplayPorts and a USB-C port.

Hardware performance improvements over previous generations stem partly from the higher-density on-die Infinity Cache design (all have 128MB) and enhanced design of the compute units, which includes a new Ray Accelerator core for each compute unit. These combine to improve the memory subsystem by reducing the latency of moving data around, increase bandwidth by up to 2.2x with a narrower path (256 bits) and deliver better energy efficiency. That also allows the processors to hit higher clock frequencies without a substantial increase in power requirements.    

Relative performance between the AMD and Nvidia cards seems to be mixed across the board as well. (It'll require a lot more testing to confirm the patterns I'm seeing.) There's a significantly smaller gap between the 6800 XT and 6800 and Nvidia's cards at 4K than at 1080p, for example, which is more than likely due to their 16GB of memory (the 3080 has 10GB) and the Infinity Cache. 

You generally don't take much of a hit going from 1080p to 1440p with AMD's cards. For instance, on Shadow of the Tomb Raider the 6800 XT dropped from 140fps to 132fps on average. The details look different, though. I noticed more reliance on the central processing unit and less consistency in the amount of time it takes to render a frame in 1440p. On the Deus Ex: Mankind Divided benchmark, the AMD cards dropped less than 3% from 1080p to 1440p. The RTX 3070 and 3080 lost about 20%.

The AMD cards also hit higher graphic processing unit clock rates for DirectX 12 calls than for DirectX 11. The GPU clock frequencies -- memory and instruction -- also vary a lot more relative to each other. By comparison, the 3070's frequencies are in lockstep. Much of this may be driver-related since AMD's driver makes more automatic on-the-fly adjustments. The behavior isn't necessarily a bad thing, just different.

There's an optimized all-AMD configuration, which takes advantage of the cards' new Smart Access Memory. SAM basically gives the card direct access to the main system memory across the system bus, rather than having to use the central processing unit as a middle man. But that's only in systems using one of the company's new Ryzen 5000 series of desktop CPUs, and AMD says it only boosts frame rates by up to 13%. I haven't had a chance to try it for want of a motherboard and CPU, though.

Between the new consoles and the barrage of graphics cards, this is an exhausting -- or exhilarating, take your pick -- time to shop for new gaming gear, especially gear that likely won't see a Black Friday discount this holiday shopping season. Toss in the supply problems we've been seeing for consoles and graphics cards, and you've got plenty of time to make a decision. As long as the prices don't get too high, or Nvidia's don't get too low, AMD's enthusiast gaming GPUs are more competitive than they've ever been.