AMD Radeon RX 6800 Review: Chipping at the Heels of the RTX 3080

AMD’s RDNA 2 based Radeon Big Navi graphics cards are finally set to hit retail today, with the RX 6800 and 6800 XT reference models expected to be available across all major markets in limited quantities. In this post, we have a look at the Radeon RX 6800 and see how it holds up compared to the competition. We’ll be checking the raster performance, ray-tracing grit, and an analysis of the much-advertised Smart Access Memory (SAM) which for the time being is exclusive to the Ryzen 5000 CPU-Radeon RDNA 2 GPU combos. Finally, we’ll also try overclocking the GPU, and yes, it does really reach 2.5-2.6GHz, unless you have a really crappy part. Read our architectural deep-dive here:

AMD Radeon RDNA 2 “Big Navi” Architectural Deep Dive: A Focus on Efficiency

Test Bench

• CPU: AMD Ryzen 5 5600X @ 5GHz
• Motherboard: ASRock X570 Taichi (Latest BIOS)
• Memory: Trident Z Royal 8GB x2 @ 3900MT/s (1:1:1)
• PSU: Corsair HX1000i

Specifications	RTX 3080	RTX 3070	Radeon RX 6800	Radeon RX 6800XT
Shaders	8704	5888	3840	4,608
Ray-Accelerators/RT Cores	68	46	60	72
Boost Clock	1710MHz	1725MHz	2,105MHz	2,250MHz
Memory	10GB GDDR6X	8GB GDDR6	16GB GDDR6	16GB GDDR6
Bus Width	320-bit	256-bit	256-bit	256-bit
Bandwidth	760GB/s	448GB/s	512GB/s	512GB/s
TMUs	272	184	240	288
ROPs	96	96	96	128
TDP	320W	220W	250W	300W
Price	$699	$499	$579	$649

Radeon RX 6800 vs RTX 3070: 1440p Gaming Benchmarks

In general, the Radeon RX 6800 is 5-10% faster than the RTX 3070, with some AMD favored titles like Shadow of the Tomb Raider and Borderlands 3 showing a delta as wide as 20-25%. In hindsight, that may seem like a good thing, but keep in mind that the former costs $79 more than the latter. Compared to the RTX 3080 ($699), the 6800 lags by ~15% on average, with some games like Metro Exodus and Strange Brigade extending it to 25%.

Radeon RX 6800 vs RTX 3070: 4K Gaming Benchmarks

At 4K, the Radeon RX 6800’s lead over the RTX 3070 grows to nearly 25%, with multiple entries seeing deltas of around 30%. An extra 25-30% performance for $79 seems rather acceptable, doesn’t it? On the other hand, the RTX 3080 continues to be 20-25% faster than the 6800 across most titles, although some do see the gap reduce to under 10% (Odyssey, Far Cry, Tomb Raider).

Radeon RX 6800 vs RTX 3070: Ray-Tracing Performance

Continued on the next page…

Yeah, it’s not pretty. The Radeon RX 6800 pretty much gets massacred in this test. It’s slower than even the last-gen GeForce RTX 2080 Ti by quite a bit and more than half as much compared to the RTX 3080. I reckon this has to do with AMD’s hybrid approach to ray-tracing where the BVH traversal is done by the shaders, while the RA units only handle the ray-box and ray-triangle tests.

NVIDIA’s RTX GPUs offload the entire RT workload to the RT cores and can concurrently run both pipelines without one affecting the other. I’m guessing the shader pipeline is stalled when AMD offloads the shader code for ray-tracing to the SIMDs.

One interesting observation I made with the ray-tracing test was that the in-game frequency dropped to just 2000MHz, all the way from 2.45-2.5GHz in rasterized titles. This could either be the result of excessive power consumption, or simply an example of the overhead penalty due to the use of shaders for BVH traversal. Read more here:

• AMD Radeon RDNA 2 “Big Navi” Architectural Deep Dive: A Focus on Efficiency

Overclocking the Radeon RX 6800: A Lot of Untapped Potential

The Radeon RX 6800 has a surprising amount of overclocking headroom. We were able to push it to as much as 2.55GHz, with rock-solid stability. There isn’t much room to increase the power and voltage, but we maxed them out. The memory was a bust. We started running into crashing even on adding just +50 to the memory offset. This is something we saw with the RDNA 1 parts as well, so it’s nothing new:

The overclocked results are quite impressive. The Radeon RX 6800 manages to nearly level with the RTX 3080 in roughly half of the games we tested, while reducing the deltas to ~8-10% in the rest. Compared to the RTX 3070, the overclocked RX 6800 is approximately 35% faster, with certain titles such as Tomb Raider seeing gains in excess of 40%. Unfortunately for NVIDIA, the RTX 3070/3080 comes with little to no overclocking headroom.

Smart Access Memory (SAM)

Unfortunately, on our system, we had a rather disappointing experience with SAM. Out of the seven games we tested, only two showed an observable gain upon turning SAM (or resizeable BAR). Far Cry 5 and SOTTR gained 2 and 3 FPS, respectively on average while the lows also improved. This is still within the margin of error, and unless I see otherwise, SAM is still just a marketing term with no significant real-world consequences.

Conclusion: Budget 4K with some Caveats

The Radeon RX 6800 is a decent product overall, but the pricing will make many mainstream gamers think twice before they make their decision. The stock performance is slightly faster or a notable step up compared to the cheaper RTX 3070, depending on the resolution you play at. At 1440p, you’re only looking at marginal gains, but the 4K performance is quite impressive, holding a lead of 25-30% over the 3070, even catching up to the RTX 3080 upon overclocking.

[taq_review]