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AMD RX 6900 XT Review

Rating: 7.0.

After getting our first look at RDNA 2 when the RX 6800 XT and RX 6800 both launched on November 18th, today our attention turns to AMD’s new flagship GPU – the RX 6900 XT. Priced at $999, or £899.99 here in the UK, the RX 6900 XT comes with 80 Compute Units, giving a total of 5120 stream processors. Designed to take the fight to Nvidia in the ultra high-end market, let’s find out if this GPU really is the RTX 3090 killer.

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With the RX 6800 XT, AMD has a highly competitive product that can really challenge the RTX 3080 with its £600 MSRP. Now, AMD has set its sights higher with the RX 6900 XT, with its marketing materials suggesting this new flagship will offer similar performance to Nvidia’s RTX 3090, but at several hundred pounds less.

Of course, we need to find out just how true those claims are, so today we look at the RX 6900 XT’s performance across 14 games, while also looking at power draw, thermals, overclocking and more.

 RX 6900 XT  RX 6800 XT RX 6800  RX 5700 XT   RX 5700
Architecture RDNA 2 RDNA 2 RDNA 2 RDNA  RDNA
Manufacturing Process 7nm 7nm 7nm 7nm  7nm
Transistor Count 26.8 billion 26.8 billion 26.8 billion 10.3 billion 10.3 billion
Die Size  519 mm² 519 mm² 519 mm² 251 mm² 251mm²
Ray Accelerators 80 72 60 n/a n/a
Compute Units  80 72 60 40 36
Stream Processors  5120 4608 3840 2560 2304
Game GPU Clock Up to 2015MHz Up to 2015MHz Up to 1815MHz Up to 1755MHz Up to 1625MHz
Boost GPU Clock Up to 2250MHz Up to 2250MHz Up to 2105MHz Up to 1905MHz Up to 1725MHz
Peak SP Performance Up to 23.04 TFLOPS Up to 20.74 TFLOPS Up to 16.17 TFLOPS Up to 9.75 TFLOPS Up to 7.95 TFLOPS
Peak Half Precision Performance Up to 46.08 TFLOPS Up to 41.47 TFLOPS Up to 32.33 TFLOPS Up to 19.5 TFLOPS Up to 15.9 TFLOPS
Peak Texture Fill-Rate Up to 720 GT/s Up to 648.0 GT/s Up to 505.2 GT/s Up to 304.8 GT/s Up to 248.4 GT/s
ROPs 128 128 96 64 64
Peak Pixel Fill-Rate Up to 288.0 GP/s Up to 288.0 GP/s Up to 202.1 GP/s Up to 121.9 GP/s Up to 110.4 GP/s
AMD Infinity Cache 128MB 128MB 128MB n/a n/a
Memory 16GB GDDR6 16GB GDDR6 16GB GDDR6 8GB GDDR6 8GB GDDR6
Memory Bandwidth 512 GB/s 512 GB/s 512 GB/s 448 GB/s 448 GB/s
Memory Interface  256-bit 256-bit 256-bit 256-bit 256-bit
Board Power  300W 300W 250W 225W 185W

While the RX 6900 XT is a new model, it has many similarities with the RX 6800 XT. Still fabricated on TSMC’s 7nm process node, it uses the same Navi 21 GPU, measuring 519 mm². The key difference is that the RX 6900 XT silicon is fully populated, with 80 Compute Units (CUs) compared to 72 for the 6800 XT. This means the new flagship has an extra 512 Stream Processors, giving a grand total of 5120 shaders.

Rated clock speed is also identical between these two RDNA 2 GPUs. This means the RX 6900 XT has a rated game clock of 2015MHz and a rated boost clock of up to 2250MHz. To put that into perspective, the RX 5700 XT has a rated game clock of 1755MHz.

AMD has also increased the memory capacity, with 16GB of GDDR6 memory found on every RX 6000 SKU (so far). The memory is clocked at 16Gbps, and operates over a 256-bit memory interface for total bandwidth of 512 GB/s. However, AMD has also implemented a 128MB Infinity Cache on the Navi 21 GPU, to significantly increase effective memory bandwidth without excess power draw.

Speaking of power, the RX 6900 XT has a rated total board power (TBP) of 300W, and this is exactly the same as the RX 6800 XT – despite having 512 more cores. From what we were told in a press briefing, it sounds like AMD has binned the 6900 XT parts for efficiency, which lets them keep to the same 300W mark while increasing core count.

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