AMD Radeon Technologies Group Previews Polaris Architecture
AMD Polaris Architecture Coming Mid-2016
In early December, I was able to spend some time with members of the newly formed Radeon Technologies Group (RTG), which is a revitalized and compartmentalized section of AMD that is taking over all graphics work. During those meetings, I was able to learn quite a bit about the plans for RTG going forward, including changes for AMD FreeSync and implementation of HDR display technology, and their plans for the GPUOpen open-sourced game development platform. Perhaps most intriguing of all: we received some information about the next-generation GPU architecture, targeted for 2016.
Codenamed Polaris, this new architecture will be the 4th generation of GCN (Graphics Core Next), and it will be the first AMD GPU that is built on FinFET process technology. These two changes combined promise to offer the biggest improvement in performance per watt, generation to generation, in AMD’s history.
Though the amount of information provided about the Polaris architecture is light, RTG does promise some changes to the 4th iteration of its GCN design. Those include primitive discard acceleration, an improved hardware scheduler, better pre-fetch, increased shader efficiency, and stronger memory compression. We have already discussed in a previous story that the new GPUs will include HDMI 2.0a and DisplayPort 1.3 display interfaces, which offer some impressive new features and bandwidth. From a multimedia perspective, Polaris will be the first GPU to include support for h.265 4K decode and encode acceleration.
This slide shows us quite a few changes, most of which were never discussed specifically that we can report, coming to Polaris. Geometry processing and the memory controller stand out as potentially interesting to me – AMD’s Fiji design continues to lag behind NVIDIA’s Maxwell in terms of tessellation performance and we would love to see that shift. I am also very curious to see how the memory controller is configured on the entire Polaris lineup of GPUs – we saw the introduction of HBM (high bandwidth memory) with the Fury line of cards.
It looks like the mobile variations of Polaris, at least, will be using standard GDDR5 memory interfaces. AMD didn’t comment more specifically than that, only elaborating that they “were invested in HBM” and that it would “continue to be on the company’s roadmap.” To me, that sounds like we’ll see a mix of products with HBM and GDDR5 technology, even in the desktop market. Likely, only more expensive, flagship graphics cards will be getting HBM.
Performance characteristics were missing from any discussions on Polaris with one exception – a demonstration of power efficiency of an unnamed Polaris GPU compared to a GeForce GTX 950 GPU. Maxwell was a big step forward for NVIDIA in terms of power efficiency and AMD is hoping that Polaris, along with the FinFET process technology, will offer an even bigger jump.
For the single data point that AMD provided, they compared the GTX 950 to a similarly priced Polaris graphics. At 1920x1080 resolution, run medium image quality settings at 60 FPS, full system power for Star Wars Battlefront was around 140 watts on the NVIDIA system. The Polaris system was using just 86 watts. That’s a difference of 54 watts, a considerable amount for GPU in this class.
It is likely that this is the first Polaris GPU being brought up (after only 2 months I’m told) and could represent the best improvement in efficiency that we will see. I’ll be curious to see how flagship GPUs from AMD compare under the same conditions.
How is Polaris able to achieve these types of improvements? It comes from a combination of architectural changes and process technology changes. Even RTG staff were willing to admit that the move to 14nm FinFET process tech was the majority factor for the improvement we are seeing here, something on the order of a 70/30 split. That doesn’t minimize the effort AMD’s engineers are going through to improve on GCN at all, just that we can finally expect to see improvements across the board as we finally move past the 28nm node.
AMD did spent quite a bit of time at the RTG summit discussing the benefits of moving to FinFET technology from the current 28nm planar technology that dominates GPU production. It’s been 5 years since we saw 28nm GPUs, BY FAR the longest stretch between node upgrades. There were just too many technical and availability issues with 22/20nm processes for either NVIDIA or AMD to adopt them. But, with FinFET 3D transistors at the 16nm and 14nm nodes, we should see sizeable improvements in power efficiency provided by its ability to have a higher “on” current and lower “off” current.
FinFET isn’t new, it’s just new to anyone other than Intel. We have been writing about 3D, FinFET transistors since 2012, with theories about its implementation and advantages for GPUs. I did learn that the first Polaris chip we saw demoed in December was built on GlobalFoundries 14nm FinFET process; whether or not AMD will also build Polaris chips on TSMC’s 16nm process has yet to be confirmed.
FinFET technologies not only offer very obvious product-level performance advantages but also lower variation. This should allow AMD (and NVIDIA) to better predict bins for this generation of GPUs. This means RTG should have no issues planning out their product line well in advance.
This chart, above, illustrates the advantages of FinFET in curves mapping power consumption and performance (clock speed). AMD’s Joe Macri stated, during our talks, that they expect this FinFET technology will bring a 50-60% power reduction at the same performance level OR a 25-30% performance increase at the same power. In theory then, if AMD decided to release a GPU with the same power consumption as the current Fury X, we might see a 25-30% performance advantage. I think, in practice, they would lower voltages a bit instead, to improve overall efficiency more dramatically, but we’ll find out in mid-2016.
One thing we will definitely see from Polaris is competition for NVIDIA in the mobile space, with Radeon GPUs finally making inroads to modern gaming notebooks. And we might be lucky enough to see further changes in the form factors available with high performance GPUs, much like we did with the Radeon R9 Nano.
But honestly, other than what we have here, very little is known about what Polaris will be and what it will offer PC gamers when it is finally released (later this year). Will AMD release mobile and mainstream GPUs first and follow up with flagship high-end parts? Or will we see the more expensive cards first in our review lineup? We don’t know and AMD and the Radeon Technologies Group aren’t talking yet. It is also going to be crucial to learn how many architecture changes will find their way to Polaris and how effective they are in change the performance efficiency for Radeon. NVIDIA’s GeForce line will be built on the same FinFET process later in 2016 so any inherent advantages of that process will apply to both parties.
Check out the video from AMD if you'd like as well.