The PS4 | Xbox One Benchmarks Thread

[Nate4Drake]

HoloDust said:

walsufnir said:

HoloDust said:

walsufnir said:

Problem is that GPGPU "steals" power from your GPU to do rendering tasks so this always comes with a trade-off. We have to see how much it can help in the future.

"The three "major modifications" Sony did to the architecture to support this vision are as follows, in Cerny's words:

• "First, we added another bus to the GPU that allows it to read directly from system memory or write directly to system memory, bypassing its own L1 and L2 caches. As a result, if the data that's being passed back and forth between CPU and GPU is small, you don't have issues with synchronization between them anymore. And by small, I just mean small in next-gen terms. We can pass almost 20 gigabytes a second down that bus. That's not very small in today’s terms -- it’s larger than the PCIe on most PCs!

• "Next, to support the case where you want to use the GPU L2 cache simultaneously for both graphics processing and asynchronous compute, we have added a bit in the tags of the cache lines, we call it the 'volatile' bit. You can then selectively mark all accesses by compute as 'volatile,' and when it's time for compute to read from system memory, it can invalidate, selectively, the lines it uses in the L2. When it comes time to write back the results, it can write back selectively the lines that it uses. This innovation allows compute to use the GPU L2 cache and perform the required operations without significantly impacting the graphics operations going on at the same time -- in other words, it radically reduces the overhead of running compute and graphics together on the GPU."

• Thirdly, said Cerny, "The original AMD GCN architecture allowed for one source of graphics commands, and two sources of compute commands. For PS4, we’ve worked with AMD to increase the limit to 64 sources of compute commands -- the idea is if you have some asynchronous compute you want to perform, you put commands in one of these 64 queues, and then there are multiple levels of arbitration in the hardware to determine what runs, how it runs, and when it runs, alongside the graphics that's in the system."

"The reason so many sources of compute work are needed is that it isn’t just game systems that will be using compute -- middleware will have a need for compute as well. And the middleware requests for work on the GPU will need to be properly blended with game requests, and then finally properly prioritized relative to the graphics on a moment-by-moment basis."

This concept grew out of the software Sony created, called SPURS, to help programmers juggle tasks on the CELL's SPUs -- but on the PS4, it's being accomplished in hardware.

The team, to put it mildly, had to think ahead. "The time frame when we were designing these features was 2009, 2010. And the timeframe in which people will use these features fully is 2015? 2017?" said Cerny.

"Our overall approach was to put in a very large number of controls about how to mix compute and graphics, and let the development community figure out which ones they want to use when they get around to the point where they're doing a lot of asynchronous compute."

Cerny expects developers to run middleware -- such as physics, for example -- on the GPU. Using the system he describes above, you can run at peak efficiency, he said.

"If you look at the portion of the GPU available to compute throughout the frame, it varies dramatically from instant to instant. For example, something like opaque shadow map rendering doesn't even use a pixel shader, it’s entirely done by vertex shaders and the rasterization hardware -- so graphics aren't using most of the 1.8 teraflops of ALU available in the CUs. Times like that during the game frame are an opportunity to say, 'Okay, all that compute you wanted to do, turn it up to 11 now.'"

http://www.gamasutra.com/view/feature/191007/inside_the_playstation_4_with_mark_.php

You don't need to post old news to reply to my post. If you read and understand what's in the text you took as a reply to me you would see that my post is still correct. There is no "unused" hardware in PS4 lying around, waiting to be used by GPGPU. It is the same hardware that is now doing rendering tasks.

Obviously I have to - if you actualy understood what is in the text, you would know what async compute is and how it runs in paralel with graphics tasks. Maybe you should re-read whole interview again bit more carefully.

I agree with you.

''Playstation 4 chief architect Mark Cerny expressed a similar vision over the potential of GPU compute during past interviews leading up to the console’s launch. He highlighted asynchronous fine-grain compute as a key feature that will give developers the headroom to explore the platform for years to come. Cerny explained that there are many situations during game applications where functions pertaining to graphics take a backseat, and that the PS4 hardware has been designed to make the most of the under-utilized portions of the GPU during such frames.''

''“If you look at the portion of the GPU available to compute throughout the frame, it varies dramatically from instant to instant. For example, something like opaque shadow map rendering doesn’t even use a pixel shader, it’s entirely done by vertex shaders and the rasterization hardware — so graphics aren’t using most of the 1.8 teraflops of ALU available in the CUs. Times like that during the game frame are an opportunity to say, ‘Okay, all that compute you wanted to do, turn it up to 11 now.”

“If you look at how the GPU and its various sub-components are utilised throughout the frame, there are many portions throughout the frame – for example during the rendering of opaque shadowmaps – that the bulk of the GPU is unused. And so if you’re doing compute for collision detection, physics or ray-casting for audio during those times you’re not really affecting the graphics. You’re utilising portions of the GPU that at that instant are otherwise under-utilised. And if you look through the frame you can see that depending on what phase it is, what portion is really available to use for compute.”

Both Katsman and Cerny are essentially talking about the same process of performing non-graphics related tasks in parallel by utilizing wasted compute resources in the GPU.

http://gearnuke.com/mantle-to-bring-ps4-asynchronous-fine-grain-compute-to-pc/

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It's not enough to read something, it must be understood.

It will take years before Devs will show what PS4 can really do.  Uncharted4 will be the 1st Game which will show something. And the 2nd Game by Naughty Dog on PS4 will be the witness of what the console can do.