wieso kommst du mit Gun an? (und wieso überhaupt kommst du jetzt mit einer Xbox Version an?) Gun ist ein schlecht programmiertes Spiel/Port, mit schlechter Engine, was auch auf PC schlecht läuft, im Gegensatz zu Tomb Raider, welches optimiert ist und eine sauber programmierte Engine nutzt und auch auf PC mit Leichtigkeit sehr gut läuft, das ist gar nicht vergleichbar.
Wenn die PS4 wirklich so stark ist, wie du behauptest, dann müssen da 60 Frames mit Leichtigkeit zu erreichen sein, sind es laut Entwickler aber nicht (und das wird man demnächst bei anderen Titeln auch noch sehen)
da wird doch rein garnichts von der power der ps4 verwendet. die ps4 wurde extra so konzipiert das anfangs schnelle port möglich sind um die konsole schnell zu pushen. wenn das erledigt ist kann man sich an die hardware der ps4 begeben und richtige next gen grafik rauspressen.
"Ultimately, we are trying to strike a balance between features which you can use day one, and features which will allow the system to evolve over the years, as gaming itself evolves," said Cerny. The "supercharged PC architecture," that the team has come up with -- to use Cerny's term --
is designed to offer significant gains the PC can't, while still offering a familiar technological environment for engineers.
What Does 'Supercharged' Mean, Anyway?
The PlayStation 4's architecture looks very familiar, at first blush -- and it is. But Cerny maintains that his team's work on it extends it far beyond its basic capabilities.
For example, this is his take on its GPU: "It's ATI Radeon. Getting into specific numbers probably doesn't help clarify the situation much, except we took their most current technology, and performed a large number of modifications to it."
To understand the PS4, you have to take what you know about Cerny's vision for it (easy to use, but powerful in the long term) and marry that to what the company has chosen for its architecture (familiar, but cleverly modified.) That's what he means by "supercharged."
"The 'supercharged' part, a lot of that comes from the use of the single unified pool of high-speed memory," said Cerny. The PS4 packs 8GB of GDDR5 RAM that's easily and fully addressable by both the CPU and GPU.
If you look at a PC, said Cerny, "if it had 8 gigabytes of memory on it, the CPU or GPU could only share about 1 percent of that memory on any given frame. That's simply a limit imposed by the speed of the PCIe. So, yes, there is substantial benefit to having a unified architecture on PS4, and it’s a very straightforward benefit that you get even on your first day of coding with the system. The growth in the system in later years will come more from having the enhanced PC GPU. And I guess that conversation gets into everything we did to enhance it."
The CPU and GPU are on a "very large single custom chip" created by AMD for Sony. "The eight Jaguar cores, the GPU and a large number of other units are all on the same die," said Cerny. The memory is not on the chip, however. Via a 256-bit bus, it communicates with the shared pool of ram at 176 GB per second.
"One thing we could have done is drop it down to 128-bit bus, which would drop the bandwidth to 88 gigabytes per second, and then have eDRAM on chip to bring the performance back up again," said Cerny. While that solution initially looked appealing to the team due to its ease of manufacturability, it was abandoned thanks to the complexity it would add for developers. "We did not want to create some kind of puzzle that the development community would have to solve in order to create their games. And so we stayed true to the philosophy of unified memory."
In fact, said Cerny, when he toured development studios asking what they wanted from the PlayStation 4, the "largest piece of feedback that we got is they wanted unified memory."
"I think you can appreciate how large our commitment to having a developer friendly architecture is in light of the fact that we could have made hardware with as much as a terabyte [Editor's note: 1000 gigabytes] of bandwidth to a small internal RAM, and still did not adopt that strategy," said Cerny. "I think that really shows our thinking the most clearly of anything."
Familiar Architecture, Future-Proofed
So what does Cerny really think the console will gain from this design approach? Longevity.
Cerny is convinced that in the coming years, developers will want to use the GPU for more than pushing graphics -- and believes he has determined a flexible and powerful solution to giving that to them. "The vision is using the GPU for graphics and compute simultaneously," he said. "Our belief is that by the middle of the PlayStation 4 console lifetime, asynchronous compute is a very large and important part of games technology."
Cerny envisions "a dozen programs running simultaneously on that GPU" -- using it to "perform physics computations, to perform collision calculations, to do ray tracing for audio."
But that vision created a major challenge: "Once we have this vision of asynchronous compute in the middle of the console lifecycle, the question then becomes, 'How do we create hardware to support it?'"
One barrier to this in a traditional PC hardware environment, he said, is communication between the CPU, GPU, and RAM. The PS4 architecture is designed to address that problem.
"A typical PC GPU has two buses," said Cerny. "There’s a bus the GPU uses to access VRAM, and there is a second bus that goes over the PCI Express that the GPU uses to access system memory. But whichever bus is used, the internal caches of the GPU become a significant barrier to CPU/GPU communication -- any time the GPU wants to read information the CPU wrote, or the GPU wants to write information so that the CPU can see it, time-consuming flushes of the GPU internal caches are required."
Enabling the Vision: How Sony Modified the Hardware
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.'"
