Radeon Pro W6800X Duo MPX Module

The Radeon Pro W6800X Duo is a dual GPU that was developed by AMD as an optional MPX module for the 3rd-generation Mac Pro. Up to two can be installed at a time (for a total of four GPUs) and it supports Infinity Fabric Link to increase the speed of inter-GPU data transmission by up to five-fold.

Description
The Radeon Pro W6800X Duo MPX Module is based on two of AMD's high-end Navi 21 workstation graphics chips that were fabricated on the 7 nm process. The GPU clock speed was 1.8 GHz, which could be boosted to 1.975 GHz, producing up to a total of 30.2 teraflops. It contained 32 GB of GDDR6 video RAM for each GPU, running at 2 GHz. It features one HDMI 2.0/2.1 port and four USB-C compatible Thunderbolt 3 ports. It could support four 5K or 6K displays, or eight 4K displays. The first Thunderbolt 3 port and the HDMI port shared a PCIe lane, reducing the output of that Thunderbolt 3 port if the HDMI port was used. The MPX module took up the space of two double-wide PCIe cards, but did not require an auxiliary power cable as it could draw all necessary power from the proprietary MPX connector.

Release
On August 3, 2021, Apple began offering the Radeon Pro W6800X Duo MPX Module as a higher-performance alternative to the preceding Radeon Pro Vega II Duo MPX Module, though the older version did remain on sale for existing users who wished to add a second matching module. The Infinity Fabric Link of the newer MPX modules are not backward compatible with the previous generation.

Issues
Apple is known to have mistakenly shipped an early Radeon Pro W6800X Duo without any exterior branding, unlike other MPX modules, which brought up concerns about the effect on resale value. The early review unit was also found to overheat, even while idling. A reviewer stated that arranging an exchange had been challenging as Apple Support insisted that this situation was an anomaly. A replacement module addressed the idling problem, but was found to still have a tendency to overheat and throttle while under load, with only marginally better performance than the preceding Radeon Pro Vega II Duo MPX Module.