In its review of PowerColor's Radeon RX 6900 XT Red Devil Ultimate, French publication Overclocking.com (opens in new tab) discovered that the graphics card is based on a new variant of the Navi 21 (Big Navi) silicon. The review brought to light the possibility that other vendors may also be preparing faster custom Radeon RX 6900 XT graphics cards.
There are currently three variations of the Navi 21 die on the market. The XL version is used in the Radeon RX 6800, the XT in the Radeon RX 6800 XT and lastly, the XTX in the Radeon RX 6900 XT. As exposed in the review, the Radeon RX 6900 XT Red Devil Ultimate leverages the Navi 21 XTXH die, which is why even the latest version of GPU-Z doesn't recognize the die. Through the help of PowerColor, Overclocking.com got its hands on the latest version of AMDVbFlash, a utility to flash firmware on Radeon graphics cards. The tool effectively confirms the existence of the Navi 21 XTXH silicon on the RX 6900 XT Red Devil Ultimate.
The Radeon RX 6900 XT already utilizes the full Navi 21 die, which brings 5,120 shading units and 80 ray tracing acceleration cores. Therefore, the XTXH variant in all likelihood is just a higher-binned die with improved clock speeds and a more generous power limit. Since AMD provides the dies to its partners, it's reasonable to think that the XTXH is AMD's idea rather than the partners doing their own binning.
Coming back to the Radeon RX 6900 XT Red Devil Ultimate, the RDNA 2 graphics card comes with two modes of operation. The silent profile limits the game and boost clocks to 2,135 MHz and 2,335 MHz, respectively, while the OC profile cranks them up to 2,235 MHz and 2,425 MHz, respectively. Basically, we're looking at a 10.9% and 7.8% higher game and boost clock speeds, respectively, in comparison to the vanilla Radeon RX 6900 XT. Does the increase warrant a new die revision? Apparently AMD (or at least PowerColor) thinks so.
Overclocking.com noticed that with the Radeon RX 6900 XT Red Devil Ultimate the core and memory frequency sliders were unlocked in AMD's Radeon software. It's uncertain if the newly lifted limits are a product of the Navi 21 XTXH's firmware. The power limit option is still locked though. But the Radeon RX 6900 XT Red Devil Ultimate has a 330W power restriction, so there is enough thermal headroom for overclocking. Overclocking.com got its sample to 2,750 MHz on air and up to 2,850 MHz under liquid nitrogen.
The Radeon RX 6900 XT Red Devil Ultimate is probably just one of many custom Radeon RX 6900 XT iterations that will leverage the Navi 21 XTXH silicon. Given the timing of the review, we wouldn't be surprised if vendors announce these higher-binned Radeon RX 6900 XT graphics cards in the next couple of days. But with the current situation for graphics cards, we fear the announcements might as well be vaporware.