GPU Enthusiasts Are Throwing a FET

The next GPU architecture from NVIDIA is expected to jump two process nodes.

NVIDIA is rumored to launch Pascal in early (~April-ish) 2016, although some are skeptical that it will even appear before the summer. The design was finalized months ago, and unconfirmed shipping information claims that chips are being stockpiled, which is typical when preparing to launch a product. It is expected to compete against AMD's rumored Arctic Islands architecture, which will, according to its also rumored numbers, be very similar to Pascal.

This architecture is a big one for several reasons.

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Image Credit: WCCFTech

First, it will jump two full process nodes. Current desktop GPUs are manufactured at 28nm, which was first introduced with the GeForce GTX 680 all the way back in early 2012, but Pascal will be manufactured on TSMC's 16nm FinFET+ technology. Smaller features have several advantages, but a huge one for GPUs is the ability to fit more complex circuitry in the same die area. This means that you can include more copies of elements, such as shader cores, and do more in fixed-function hardware, like video encode and decode.

That said, we got a lot more life out of 28nm than we really should have. Chips like GM200 and Fiji are huge, relatively power-hungry, and complex, which is a terrible idea to produce when yields are low. I asked Josh Walrath, who is our go-to for analysis of fab processes, and he believes that FinFET+ is probably even more complicated today than 28nm was in the 2012 timeframe, which was when it launched for GPUs.

It's two full steps forward from where we started, but we've been tiptoeing since then.

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Image Credit: WCCFTech

Second, Pascal will introduce HBM 2.0 to NVIDIA hardware. HBM 1.0 was introduced with AMD's Radeon Fury X, and it helped in numerous ways — from smaller card size to a triple-digit percentage increase in memory bandwidth. The 980 Ti can talk to its memory at about 300GB/s, while Pascal is rumored to push that to 1TB/s. Capacity won't be sacrificed, either. The top-end card is expected to contain 16GB of global memory, which is twice what any console has. This means less streaming, higher resolution textures, and probably even left-over scratch space for the GPU to generate content in with compute shaders. Also, according to AMD, HBM is an easier architecture to communicate with than GDDR, which should mean a savings in die space that could be used for other things.

Third, the architecture includes native support for three levels of floating point precision. Maxwell, due to how limited 28nm was, saved on complexity by reducing 64-bit IEEE 754 decimal number performance to 1/32nd of 32-bit numbers, because FP64 values are rarely used in video games. This saved transistors, but was a huge, order-of-magnitude step back from the 1/3rd ratio found on the Kepler-based GK110. While it probably won't be back to the 1/2 ratio that was found in Fermi, Pascal should be much better suited for GPU compute.

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Image Credit: WCCFTech

Mixed precision could help video games too, though. Remember how I said it supports three levels? The third one is 16-bit, which is half of the format that is commonly used in video games. Sometimes, that is sufficient. If so, Pascal is said to do these calculations at twice the rate of 32-bit. We'll need to see whether enough games (and other applications) are willing to drop down in precision to justify the die space that these dedicated circuits require, but it should double the performance of anything that does.

So basically, this generation should provide a massive jump in performance that enthusiasts have been waiting for. Increases in GPU memory bandwidth and the amount of features that can be printed into the die are two major bottlenecks for most modern games and GPU-accelerated software. We'll need to wait for benchmarks to see how the theoretical maps to practical, but it's a good sign.