Review: AMD Radeon RX 6900 XT

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Radeon has lagged behind Ryzen for nearly three years. Chief amongst the reasons for this state of affairs is the strength of competitor Nvidia, whose latest Ampere-based 30-series cards are impressive.

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But Radeon is getting its act together. Targeting the premium end of the market, the latest Big Navi gives Ampere a run for its money in rasterisation-only titles. Lagging behind in ray tracing and with no DLSS-like technology available in 2020, our nod still goes to the green team. Such thoughts are underscored by a painful lack of stock from both companies, particularly AMD.

Seemingly unperturbed by retail availability, AMD is continuing the Big Navi journey by officially releasing the fastest model yet. Enter the Radeon RX 6900 XT.

From Small Navi To Big Navi

Radeon RX 6900 XT Radeon RX 6800 XT Radeon RX 6800 Radeon RX 5700 XT Radeon RX 5700
Launch date December 2020 November 2020 November 2020 July 2019 July 2019
Codename Navi 21 Navi 21 Navi 21 Navi 10 Navi 10
Architecture RDNA 2 RDNA 2 RDNA 2 RDNA RDNA
Process (nm) 7 7 7 7 7
Transistors (bn) 26.8 26.8 26.8 10.3 10.3
Die Size (mm²) 519 519 519 251 251
Full Implementation of Die Yes No No Yes No
Hardware Raytracing Yes Yes Yes No No
Infinity Cache Yes Yes Yes No No
Compute Units 80 72 60 40 36
Processors 5,120 4,608 3,840 2,560 2,304
Texture Units 320 288 240 160 144
ROP Units 128 128 96 64 64
Boost Clock (MHz) 2,250 2,250 2,105 1,905 1,725
Game Clock (MHz) 2,015 2,015 1,815 1,755 1,625
Peak GFLOPS (SP) 23,040 20,736 16,166 9,750 7,950
Memory Size (GB) 16 16 16 8 8
Memory Clock (MHz) 16,000 16,000 16,000 14,000 14,000
Memory Bus (bits) 256 256 256 256 256
Max Bandwidth (GB/s) 512 512 512 448 448
PCIe Support Gen 4 Gen 4 Gen 4 Gen 4 Gen 4
Power Connectors 8+8 8+8 8+8 6+8 6+8
TDP (watts) 300 300 250 225 180
GFLOPS per watt 76.8 69.1 64.66 43.3 44.2
Launch MSRP $999 $649 $579 $399 $349

Radeon RX 6900 XT Analysis

The table summarises the many similarities between the 6000 Series line-up. This most powerful of Navi products uses the same 26.8bn transistor die but in a fuller form comprising 80 Compute Units compared to 72 and 60 for RX 6800 XT and RX 6800, respectively.

It makes most sense to compare to the released RX 6800 XT, so this new head honcho, keeping to the same prescribed frequencies, has 11 per cent more capability for shading, texturing, rendering and ray tracing. The back end, meanwhile, remains exactly the same.

The difference between the top two Radeons GPUs is not as significant as for Nvidia’s RTX 3090 and 3080, but then neither is price. With stock expected to be extremely limited, AMD can actually charge what it wants and sell out. Even so, the SEP is $999. It’s been a long time since AMD could genuinely charge that amount for a consumer graphics card.

Radeon RX 6900 XT uses the best Big Navi silicon available at foundry partner TSMC. We know this because it can pull in those extra 8 CUs without increasing total board power over RX 6800 XT, which remains at a reasonable 300W. There’s no messing with proprietary connectors as the Made By AMD (MBA) board features dual 8-pin power.

Though nominal frequencies are rated the same as RX 6800 XT, AMD expects the top dog model to scale higher. Accordingly, the recommended PSU is 850W, up from 750W, and maximum overclocking frequency setting is 3.0GHz, compared to 2.8GHz for the $649 board.

There are no fundamental changes to architecture between Big Navi chips, so that means all share the same-speed 128MB Infinity Cache sitting between regular GPU cache and 16GB of GDDR6 memory.

With all this in mind, expect Radeon RX 6900 XT to put around 10 per cent into the RX 6800 XT when gaming becomes bound by the GPU. Good enough to challenge the mighty GeForce RTX 3090? AMD believes so, but carry on reading to find out what we think.

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