Introduction

The XFX Radeon RX 6800 XT Speedster Merc 319 Black is the company’s fastest custom-design RX 6800 XT “Big Navi” graphics card, designed to offer maximum performance out of the box for the RX 6800 XT, the highest overclocking headroom, and the quietest cooler when gaming. The Speedster Merc 319 (where “Merc” is a contraction of the word “mercury,” not “mercenary”) is the company’s successor to its popular THICC III line of graphics cards based on the original RX 5700 series “Navi.” XFX has taken many lessons from the THICC, in giving the Merc 319 much better ventilation and heat dissipation, and paired it with a custom-design PCB with an incredibly powerful custom VRM solution.

AMD’s new RDNA2 graphics architecture at the heart of “Big Navi” is built on the philosophy of using enormous amounts of compute power to accomplish real-time raytracing, and full DirectX 12 Ultimate logo compliance for the latest generation of AAA games. The most compute-intensive part of raytracing is performed by fixed-function hardware called Ray Accelerators. To accomplish its design goals, AMD doubled the SIMD muscle of “Big Navi” over the previous generation, which should also result in an enormous performance uplift with conventional raster 3D rendering, which still makes up the vast majority of 3D gaming. AMD is hence marketing the RX 6800 XT as a card for maxed-out 4K Ultra HD gaming, as well as extreme refresh-rate esports gaming.

The RX 6800 XT Speedster Merc 319 Black is based on the new 7 nm “Navi 21” silicon by AMD, which features 72 RDNA2 compute units, working out to 4,608 stream processors. Each of these CUs has one Ray Accelerator. AMD also bolstered the memory sub-system by giving the card 16 GB of GDDR6 memory running at 16 Gbps. The memory bus width is 256-bit wide, which works out to 512 GB/s of raw memory bandwidth, but AMD has deployed an interesting solution called Infinity Cache to improve memory sub-system performance. This is a 128 MB last-level cache on the “Navi 21” silicon with an enormous bandwidth the GPU can use as a fast scratchpad. Our RX 6800 XT reference-design review takes an in-depth look at the RDNA2 architecture.

As mentioned earlier, the XFX Radeon RX 6800 XT Merc 319 Black pairs AMD’s swanky new GPU with a powerful triple-slot cooling solution that uses a large aluminium fin-stack heatsink ventilated by a trio of fans. The metal cooler shroud and backplate feature perforations to enable free flow of heat exhaust. The card is longer than the PCB underneath, so some of the airflow from the third fan flows through—the “hottest” design trend with graphics cards of this generation. XFX has also given the RX 6800 XT a factory overclock, with its engine boost frequency now dialed up to 2360 MHz (compared to 2250 MHz reference). XFX is pricing the card at $800, a $150 premium over the $650 baseline price for the RX 6800 XT. In this review, we take a close look at this dapper-looking card.