The NVIDIA GeForce GTX 1080 & GTX 1070 Founders Editions Review: Kicking Off the FinFET Generation
by Ryan Smith on July 20, 2016 8:45 AM ESTGP104: The Heart of GTX 1080
At the heart of the GTX 1080 is the first of the consumer-focused Pascal GPUs, GP104. Though no two GPU generations are ever quite alike, GP104 follows a number of design cues established with the past couple 104 GPUs. Overall 104 GPUs have struck a balance between size and performance, allowing NVIDIA to get a suitably high yielding GPU out at the start of a generation, and to be followed up with larger GPUs later on as yields improve. With the exception of the GTX 780, 104 GPUs been the backbone of NVIDIA’s GTX 70 and 80 parts, and that is once again the case for the Pascal generation.
In terms of die size, GP104 comes in at 314mm2. This is right in NVIDIA’s traditional sweet spot for these designs, slotting in between the 294mm2 GK104 and the 332mm2 GF104. In terms of total transistors we’re looking at 7.2B transistors, up from 3.5B on GK104 and the 5.2B of the more unusual GM204. The significant increase in density comes from the use of TSMC’s 16nm FinFET process, which compared to 28nm combines a full node shrink, something that has been harder and harder to come by as the years have progressed.
Though the density improvement offered by TSMC’s 16nm process is of great importance to GP104’s overall performance, for once density takes a back seat to the properties of the process itself. I am of course speaking about the FinFET transistors, which are the headlining feature of TSMC’s process.
We’ve covered FinFET technology in depth before, so I won’t completely rehash it here. But in brief, FinFETs are an important development for chip fabrication as processes have gone below 28nm. As traditional, planar transistors have shrunk in feature size – and ultimately, the number of atoms they’re comprised of – electrical leakage has increased. With fewer atoms in a transistor, there are equally fewer atoms to control the flow of electrons.
FinFET in turn is a solution to this problem, essentially allowing fabs to turn back the clock on electrical leakage. By building transistors as three-dimensional objects with height as opposed to two-dimensional objects, giving FinFET transistors their characteristic fins in the process, FinFET technology greatly reduces the amount of energy a transistor leaks. In practice what this means is that FinFET technology not only reduces the total amount of energy wasted from leakage, but it also allows transistors to be operated at a much lower voltage, something we’ll see in depth with our analysis of GTX 1080.
FinFETs, or rather the lack thereof, are a big part of why we never saw GPUs built on TSMC’s 20nm process. It was TSMC’s initial belief that they could contain leakage well enough using traditional High-K Metal Gate (HKMG) technology on 20nm, a bet they ultimately lost. At 20nm, planar transistors were just too leaky to use for many applications, which is why ultimately we only saw SoCs on 20nm (and even then they were suboptimal). FinFETs, as it turns out, are absolutely necessary to get good performance out of transistors built on processes below 28nm.
And while it took TSMC some time to get there, now that they have the capability NVIDIA can reap the benefits. Not only can NVIDIA finally build a relatively massive chip like a GPU on a sub-28nm process, but thanks to the various beneficial properties of FinFETs, it allows them to take their designs in a different direction than what they could do on 28nm.
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Ryan Smith - Friday, July 22, 2016 - link
2) I suspect the v-sync comparison is a 3 deep buffer at a very high framerate.lagittaja - Sunday, July 24, 2016 - link
1) It is a big part of it. Remember how bad 20nm was?The leakage was really high so Nvidia/AMD decided to skip it. FinFET's helped reduce the leakage for the "14/16"nm node.
That's apples to oranges. CPU's are already 3-4Ghz out of the box.
RX480 isn't showing it because the 14nm LPP node is a lemon for GPU's.
You know what's the optimal frequency for Polaris 10? 1Ghz. After that the required voltage shoots up.
You know, LPP where the LP stands for Low Power. Great for SoC's but GPU's? Not so much.
"But the SoC's clock higher than 2Ghz blabla". Yeah, well a) that's the CPU and b) it's freaking tiny.
How are we getting 2Ghz+ frequencies with Pascal which so closely resembles Maxwell?
Because of the smaller manufacturing node. How's that possible? It's because of FinFET's which reduced the leakage of the 20nm node.
Why couldn't we have higher clockspeeds without FinFET's at 28nm? Because power.
28nm GPU's capped around the 1.2-1.4Ghz mark.
20nm was no go, too high leakage current.
16nm gives you FinFET's which reduced the leakage current dramatically.
What does that enable you to do? Increase the clockspeed..
Here's a good article
http://www.anandtech.com/show/8223/an-introduction...
lagittaja - Sunday, July 24, 2016 - link
As an addition to the RX 480 / Polaris 10 clockspeedGCN2-GCN4 VDD vs Fmax at avg ASIC
http://i.imgur.com/Hdgkv0F.png
timchen - Thursday, July 21, 2016 - link
Another question is about boost 3.0: given that we see 150-200 Mhz gpu offset very common across boards, wouldn't it be beneficial to undervolt (i.e. disallow the highest voltage bins corresponding to this extra 150-200 Mhz) and offset at the same time to maintain performance at lower power consumption? Why did Nvidia not do this in the first place? (This is coming from reading Tom's saying that 1060 can be a 60w card having 80% of its performance...)AnnonymousCoward - Thursday, July 21, 2016 - link
NVIDIA, get with the program and support VESA Adaptive-Sync already!!! When your $700 card can't support the VESA standard that's in my monitor, and as a result I have to live with more lag and lower framerate, something is seriously wrong. And why wouldn't you want to make your product more flexible?? I'm looking squarely at you, Tom Petersen. Don't get hung up on your G-sync patent and support VESA!AnnonymousCoward - Thursday, July 21, 2016 - link
If the stock cards reach the 83C throttle point, I don't see what benefit an OC gives (won't you just reach that sooner?). It seems like raising the TDP or under-voltaging would boost continuous performance. Your thoughts?modeless - Friday, July 22, 2016 - link
Thanks for the in depth FP16 section! I've been looking forward to the full review. I have to say this is puzzling. Why put it on there at all? Emulation would be faster. But anyway, NVIDIA announced a new Titan X just now! Does this one have FP16 for $1200? Instant buy for me if so.Ryan Smith - Friday, July 22, 2016 - link
Emulation would be faster, but it would not be the same as running it on a real FP16x2 unit. It's the same purpose as FP64 units: for binary compatibility so that developers can write and debug Tesla applications on their GeForce GPU.hoohoo - Friday, July 22, 2016 - link
Excellent article, Ryan, thank you!Especially the info on preemption and async/scheduling.
I expected the preemption mght be expensive in some circumstances, but I didn't quite expect it to push the L2 cache though! Still this is a marked improvement for nVidia.
hoohoo - Friday, July 22, 2016 - link
It seems like the preemption is implemented in the driver though? Are there actual h/w instructions to as it were "swap stack pointer", "push LDT", "swap instruction pointer"?