GeForce GTX1060: nVidia brings Pascal to the masses

Right, we can be short about the GTX1060… It does exactly what you’d expect: it scales down Pascal as we know it from the GTX1080 and GTX1070 to a smaller, cheaper chip, aiming at the mainstream market. The card is functionally exactly the same, apart from missing a SLI connector.

But let’s compare it to the competition, the RX480. And as this is a technical blog, I will disregard price. Instead, I will concentrate on the technical features and specs.

RX480:
Die size: 230 mm²
Process: GloFo 14 nm FinFET
Transistor count: 5.7 billion
TFLOPS: 5.1
Memory bandwidth: 256 GB/s
Memory bus: 256-bit
Memory size: 4/8 GB
TDP: 150W
DirectX Feature level: 12_0

GTX1060:
Die size: 200 mm²
Process: TSMC 16 nm FinFET
Transistor count: 4.4 billion
TFLOPS: 3.8
Memory bandwidth: 192 GB/s
Memory bus: 192-bit
Memory size: 6 GB
TDP: 120W
DirectX Feature level: 12_1

And well, if we would just go by these numbers, then the Radeon RX480 looks like a sure winner. On paper it all looks very strong. You’d almost think it’s a slightly more high-end card, given the higher TDP, the larger die, higher transistor count, higher TFLOPS rating, more memory and more bandwidth (the specs are ~30% higher than the GTX1060). In fact, the memory specs are identical to that of the GTX1070, as is the TDP.

But that is exactly where Pascal shines: due to the excellent efficiency of this architecture, the GTX1060 is as fast or faster than the RX480 in pretty much all benchmarks you care to throw at it. If this would come to a price war, nVidia would easily win this: their GPU is smaller, their PCB can be simpler because of the smaller memory interface, and the lower power consumption, and they can use a smaller/cheaper cooler because they have less heat to dissipate. So the cost for building a GTX1060 will be lower than that of a RX480.

Anyway, speaking of benchmarks…

Time Spy

FutureMark recently released a new benchmark called Time Spy, which uses DirectX 12, and makes use of that dreaded async compute functionality. As you may know, this was one of the points that AMD has marketed heavily in their DX12-campaign, to the point where a lot of people thought that:

1. AMD was the only one supporting the feature
2. Async compute is the *only* new feature in DX12
3. All gains that DX12 gets, come from using async compute (rather than the redesign of the API itself to reduce validation, implicit synchronization and other things that may reduce efficiency and add CPU overhead)

Now, the problem is… Time Spy actually showed that GTX10x0-cards gained performance when async compute was enabled! Not a surprise to me of course, as I already explained earlier that nVidia can do async compute as well. But many people were convinced that nVidia could not do async compute at all, not even on Pascal. In fact, they seemed to believe that nVidia hardware could not even process in parallel period. And if you take that as absolute truth, then you have to ‘explain’ this by FutureMark/nVidia cheating in Time Spy!

Well, of course FutureMark and nVidia are not cheating, so FutureMark revised their excellent Technical Guide to deal with the criticisms, and also published an additional press release regarding the ‘criticism’.

This gives a great overview of how the DX12 API works with async compute, and how FutureMark made use of this feature to boost performance.

And if you want to know more about the hardware-side, then AnandTech has just published an excellent in-depth review of the GTX1070/1080, and they dive deep into how nVidia performs asynchronous compute and fine-grained pre-emption.

I was going to write something about that myself, but I think Ryan Smith did an excellent job, and I don’t have anything to add to that. TL;DR: nVidia could indeed do async compute, even on Maxwell v2. The scheduling was not very flexible however, which made it difficult to tune your workload to get proper gains. If you got it wrong, you could receive considerable performance hits instead. Therefore nVidia decided not to run async code in parallel by default, but just serialize it. The plan may have been to ‘whitelist’ games that are properly optimized, and do get gains. We see that even in DOOM, the async compute path is not enabled yet on Pascal. But the hardware certainly is capable of it, to a certain extent, as I have also said before. Question is: will anyone ever optimize for Maxwell v2, now that Pascal has arrived?

Update: AMD has put a blog-post online talking about how happy they are with Time Spy, and how well it pushes their hardware with async compute: http://radeon.com/radeon-wins-3dmark-dx12

I suppose we can say that AMD has given Time Spy its official seal-of-approval (publicly, that is. They already approved it within the FutureMark BDP of course).