NVIDIA’s RTX cards are a gamble on the future of gaming

And that’s nothing to do with ray-tracing.

NVIDIA's RTX series of GPUs has been a long time coming. The company's last meaningful hardware revision, the 10 series, came out back in May 2016. And real-time ray-tracing, the intensive rendering technique that RTX cards purportedly make a reality, has been dreamed about for decades. But, although it hasn't dominated the headlines as much, the most important change RTX brings is the shift away from raw power and towards algorithms and AI.

But, I'm getting ahead of myself. First, let's have a quick look at what exactly NVIDIA is trying to sell you. Next week, two cards, the $700 RTX 2080 and $1,000 RTX 2080 Ti, will be vying for your cash, followed in October by the RTX 2070, which at $500 is likely to be the best seller of the three.

Starting at the bottom, in terms of raw power, the RTX 2070 is roughly equivalent to the GTX 1080; the RTX 2080 goes toe to toe with the GTX 1080 Ti; the RTX 2080 Ti is in a league of its own. The 2070 and 2080 have 8GB of GDDR6 RAM; the 2080 Ti has 11GB. All three are based on the company's new Turing architecture, which means they have cores dedicated to AI (Tensor) and ray-tracing (RT).

	GTX 2080 TI	GTX 2080	GTX 2070
CUDA cores	4,352	2,944	2,304
Tensor cores	544	368	288
RT cores	68	46	36
Memory	11GB GDDR6	8GB GDDR6	8GB GDDR6
Memory bandwidth (GB/sec)	616	448	448
TFLOPS	13.4*	10*	7.5*
Price	$999*	$699*	$499*

*The 2080 Ti Founders Edition costs $200 more, the 2070 and 2080 Founders Editions cost $100 more. All have higher clock speeds for a 5 to 6 percent improvement in TFLOPS.

Expect a fourth card, likely the RTX 2060, to bring the entry price down significantly in the coming months, followed by a slew of cut-down options for budget-minded gamers (the 10 series made its way down to the sub-$100 GTX 1030). There's also room at the top end for expansion: The RTX 2080 Ti Founders Edition can handle 14.2 trillion floating-point operations per second (TFLOPS), while the Turing TU102 chip these new cards are based on pushes that figure up to 16.3 TFLOPS. That's achieved through a mix of higher clock speeds and more CUDA cores (the 2080 Ti has 4,352, the fully configured TU102 has 4,608.)

RTX also arrives with a lot of under-the-hood improvements. There's a faster caching system with a shared memory architecture, a new graphics pipeline and concurrent processing of floating and integer calculations. If that means nothing to you, don't worry too much: The takeaway from that word soup is not only does the RTX range have more raw power, but it uses that power more efficiently.

And that's the key here. Ray-tracing stole the headlines, and I'm intrigued to see how developers use it, but it's efficiency that really excites me about RTX.

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The ultimate goal of a game system, be it a $2,000 gaming PC or a $300 Nintendo Switch, is to calculate a color value for each pixel on a screen. Even a simplified guide on how a modern graphics pipeline does this would run the length of a novella, but here's a three-sentence summary: CPUs aren't made to render modern graphics. Instead, a CPU sends a plan for what it wants to draw to a GPU, which has hundreds or thousands of cores that can work independently on small chunks of an image. The GPU executes on the CPU's plan, running shaders -- very small programs -- to define the color of each pixel.

The challenge for both graphics-card manufacturers and game developers, then, is scale. That $300 Switch, in portable mode, typically calculates 27-million pixel values a second, which it can do just fine with a three-year-old mobile NVIDIA chip. If you're targeting 4K at 60FPS (which is what many gamers buying RTX cards want) your system needs to push out close to half-a-billion pixels a second. That puts a huge strain on a system, especially when you consider that your PC isn't just picking these colors out of thin air, and is instead simulating a complex 3D environment in real time as part of the calculations.

There are already plenty of techniques used to reduce that strain. One is rendering all or parts of a scene at a lower resolution and stretching the results out. This is super obvious when you have a game running at 720p on a 1080p screen, but less so when, say, a fog cloud is being drawn at quarter-resolution. And that's what NVIDIA's optimizations are all about: cutting down the quality in places you won't notice.

NVIDIA's new graphics pipeline can employ several new shading techniques to cut corners. In many ways, this builds on less-flexible power-saving measures utilized for VR, like MRS (multi-resolution shading) and LMS (lens-matched shading). In the image above, you're seeing a GPU breaking a scene down into a grid in real time. The uncolored squares are high-detail, and shaded at a 1:1 ratio, just like a regular game scene. The colored ones don't need the same level of attention. The red squares, for example, are only shaded in 4x4 pixel blocks, while more-detailed but non-essential blue squares are shaded in 2x2 blocks. Given the low detail level of those areas of the image, the change is essentially unnoticeable.

You can take this basic concept, that pixel-shading rates don't have to be fixed throughout an image, and apply it in targeted ways. In racing games your gaze is basically fixed on your car and the horizon. The pixels in the central and top half of the screen could be filled in at 1:1, but the corners could be 4x4. (With 2x2 and 2x1 blocks in between easing the transition, of course.) This, NVIDIA says, will basically be imperceivable in motion and decreases the load on the shading cores, allowing for higher frame rates.

NVIDIA is working on more advanced shading techniques that will, for example, allow developers to reuse texture shading over multiple frames or change the quality of shading on moving objects that your eyes can't resolve. They're all efficiency plays, intended to squeeze more out of the same hardware. One example shown to press last month at the RTX launch had Wolfenstein II: The New Colossus running with adaptive shading: NVIDIA said it could provide a 15-to-20-percent improvement in frame rates with negligible image compromises.