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PS4 & Unified Memory Pool - How Substantial?
- Thread starter Dunk#7
- Start date
close to the edge
Member
The PS4 and the Xbox One also both have ways to access the hardware (the graphics hardware in particular) at a much lower level than is usually possible on PCs. On a PC, every modern game (that I know of) goes through either OpenGL or DirectX. That has a big potential for optimizations, but it also has a pretty big learning curve, especially when you're coming from PC development.
On topic, I think it's not gonna be a big deal in the early stages of the system. Currently, data from the CPU's RAM is copied to the GPU in big batches (ideally). The unified memory means that there is no such restriction, since both GPU and CPU have access to the same memory pool. Cerny mentioned in an interview that in a few years, people will have figured out when and how the GPU is not busy and that it'll be possible to offload work from the CPU that would otherwise only be calculated on the CPU.
James Sawyer Ford
Banned
It won't matter that games will be more graphically amazing on one platform?
That's basically like saying "graphics don't matter".
NullPointer
Member
It mattered for Sony this gen, having the weaker multiplatform support. If there's a difference, it'll matter.
And Sony had much greater third party support the gen before despite having vastly weaker hardware.
The install bases these consoles establish (and more importantly the software sales that come from those install bases) will matter more for third-party support than the hardware capabilities.
Unless you mean the capability of the hardware will affect where you buy multi-platform games personally, in which case I certainly can't argue. I bought most multi-plats on Xbox and then 360 because they were better, and will continue to do the same on PS4.
Dictator93
Member
thx mate
RibbedHero
Member
So almost nothing to do with the thread at hand. Got it.
Everything you said here has nothing to do with videogames having muted colours.
The number of simultaneous colours you can store/compute has no impact on which individual colour a game uses, especially when we're talking about >8bit per channel depth, though even that isn't necessary (paletised textures) . Games have muted colours because the designers wanted it that way.
How so? The end result of all the technical wizz bang is how does it affect the games. Does the tech create better graphics, higher resolutions, more stable frame rates, or additional characters on screen? Otherwise, what would be the point of it all? The forum isn't about discussing how quick the devices are at crunching numbers in spreadsheets. I'm arguing that Sony has the better tech, but that only Sony's first party studios will really take advantage of it.
James Sawyer Ford
Banned
You're still going to get multiplatform games running better on PS4, even if they're in the same league of quality with XB1 multiplatforms -- better resolution, framerate, effects, textures, AA, image quality, etc. The differences should be more noticeable than last gen due to the size of the hardware disparity and similarity in architecture.
qa_engineer
Member
I do recall Cerny mentioning in his interview with gamasutra that Sony modified the APU architecture so that the GPU would have direct access to memory, bypassing the L1/L2 cache as a whole. The bus has a peak of 20gbs which is pretty fast. This allows the GPU and CPU to access memory at the same time and therefore there is less idle time and devs can really flex that gpgpu muscle. AMD's marketing buzzword for this is "hUMA" or heterogenous uniform memory access.
Edit: found it
http://www.gamasutra.com/view/feature/191007/inside_the_playstation_4_with_mark_.php?page=2
Edit: found it
http://www.gamasutra.com/view/feature/191007/inside_the_playstation_4_with_mark_.php?page=2
Nice thread derail.
I dont think the third parties will devote the extra resources to make their games look that different. Also, you're still going to get multi platform games running better, being cheaper, and infinitely backwards compatible on pc.
I agree that they won't spend much effort, but making things look a little better on PS4 will be basically effortless unless there's something major we don't know about the X1. The power difference is less than Xbox vs. PS2, but much like that generation, the extra power will be very easy to use.
James Sawyer Ford
Banned
You don't have to devote resources to make them look better, given the architectural similarities.
It's just like running the same game on two different GPUs from the same vendor.
The games will just run on higher settings or framerate/resolution automatically.
SkullHydra
Member
You said that developers won't devote resources to use the extra power of the PS4, but then mention that the PC version will be better? How do you think the PC has the better multiplats, if the developers don't take the time to optimize it? Why would they take advantage of the specs that PCs can have, but not the PS4?
googleplex
Member
qa_engineer
Member
smokeandmirrors
Banned
And if all else fails, just write it in x86-64 ASM. Because reasons.
But how much lower can it go at this point. I'd always assumed that OpenGL and DirectX were mature and speedy enough, unless you're counting having to deal with all the other bullshit that goes on in the background on a modern OS?
I also assumed that the PS3 was using some stripped down form of OpenGL 1.0? So I guess the stripped down form and libgcm as i think it is, really makes that big of a difference?
I have a semester of OpenGL work and went back to toying with it again tonight, so my knowledge is extremely limited in that regard.
njean777
Member
Holy shit I feel bad for the engineers that had to read all that, I would feel bummed if I read all that and now we are moving on.
Yeah, November 2014, when Naughty Dog fully uses this advantage for Uncharted 4.
Pretty excited about new Killzone and Drive Club personally. Looking at Evolution's E3 showing of Motorstorm leading up to release, the difference between that the final game was night and day graphically, I have full confidence Drive Club is going to be amazing.
The primary advantage is coding to a fixed hardware target. You know exactly where the issues and bottlenecks are, and you can work around them on a closed platform. In an open platform like PC, you are stuck throwing excess power at most issues because the code has to work on a broad range of hardware.
Lauch games are about 3 months from Beta, I won't expect miracles, if they don't look fantastic/run super smooth already.
smokeandmirrors
Banned
Yeah. I'm just wondering how much lower level these API's can be..
Actually I should probably just look into how this stuff is rendered. Time to brush up on Linear Algebra and give a look under the hood.
qa_engineer
Member
Actually the ability for the GPU to have full access, or fully adddres main memory was only made available recently with their Richland and Kaveri products. Trinity apus could access all shared memory, but only through HSA MMU
http://arstechnica.com/information-...orm-memory-access-coming-this-year-in-kaveri/
I've got a few general questions about UMA as well:
How is the issue of memory contention mitigated? Is there a built in mechanism in the memory controller to deal with this, or do programmers have to manually manage memory usage within the game program?
How does the memory controller juggle requests? First come first served? Split up access into time slices and proportionally distribute access time? Is memory access distributed using some sort of time share scheme where both the CPU and the GPU are assigned their own reserved access windows?
The system memory bandwidth is 176 GB/s, the NB to CPU bandwidth is ~20 GB/s. Is the latter merely a restriction in the form of a bandwidth cap or is that the interconnect design limit. If the latter is true wouldn't CPU memory access bring system memory speed down to 20 GB/s? I'm guessing the on demand distribution proposed above in conjunction with some buffers on the memory controller could help avoid this.
The split memory issue on the PS3: Was this because the pools were too small (also the GPU bandwidth sucked)? Would a split of 8GB DDR3 @ ~30GB/s for system RAM and 2 GB GDDR5 @ 192GB/s for the VRAM be preferable to UMA or the opposite?
How is the issue of memory contention mitigated? Is there a built in mechanism in the memory controller to deal with this, or do programmers have to manually manage memory usage within the game program?
How does the memory controller juggle requests? First come first served? Split up access into time slices and proportionally distribute access time? Is memory access distributed using some sort of time share scheme where both the CPU and the GPU are assigned their own reserved access windows?
The system memory bandwidth is 176 GB/s, the NB to CPU bandwidth is ~20 GB/s. Is the latter merely a restriction in the form of a bandwidth cap or is that the interconnect design limit. If the latter is true wouldn't CPU memory access bring system memory speed down to 20 GB/s? I'm guessing the on demand distribution proposed above in conjunction with some buffers on the memory controller could help avoid this.
The split memory issue on the PS3: Was this because the pools were too small (also the GPU bandwidth sucked)? Would a split of 8GB DDR3 @ ~30GB/s for system RAM and 2 GB GDDR5 @ 192GB/s for the VRAM be preferable to UMA or the opposite?
Sushen
Member
3 month is a long time in game development, although I feel sorry for the devs going through the crunch; must be pretty miserable.
I'd guess it will remain a topic of debate until the first few multiplatform comparisons are out. At which point the discussion will refocus on the comparatively small differences between XB1 and PS4 versions. Call it a hunch.
OldAsUrSock
Banned
You can't optimize on PC because you can't code to the metal.
Dictator93
Member
pretty sure the highest end PCs are already crushing its performacne.
I am hoping for some great GPU-CPU interaction on the PS4 though with some very unique effects or techniques coming out of that. That linked article about a-syncronous AA from Intel are things that I think will be infintely more possible on PS4... to make it more even with higherend brute force PCs.... obviously not the same... but closer.
qa_engineer
Member
I know. I already posted that link on page 1.
I was talking about the modiftications that Mark Cerny adressed explicitly in his interview with Gamasutra. You're completely right anyway, but I just wanted to pointed out that the things Cerny mentioned are not some alientech that fell from heaven. The combination of these features (some of it are HSA, some of it are GCN) in conjunction with a low level API however, will make it a unique and extremely powerful system. And as far as I know he never talked directly about cache coherency and unified adress space which are the features that are distinct from AMDs earlier APU designs.
Mark Cerny built a great system. It looks flawless to me. I mean just take a look at the reactions of the developers: They completely went bananas when Cerny said on stage that PS4 will have 8GB of GDDR5 because they knew exactly that he was talking about a pool with uniform memory access. That's just unreal! Did you see anyone flip out because of XBox One's hardware? But the HSA is an extremely complicated thing. It is almost impossible for Cerny to explain the benefits of this architecture to the masses and even more so since PS4 can't compete with a GeForce Titan on paper. Just take a look at the reactions of the PC master race: "This is just a mid-range GPU!!!!111" No, it's not! PS4 is marvelous tech. I hope people will see that sooner or later.
Right. I don't think Cerny was going to provide an overly detailed overview of all the various features they added, or modifications made, or explain allof the benefits of having such features. He spoke in generalities to get the design points across and it was effective. Those who follow CPU/GPU tech will read that artricle and say, "Yep. The PS4 chipset has AMD's hUMA feature set."
I don't think it's a fair comparison to make when looking at a 1.84 teraflop part in a closed system to a 3-5 teraflop mainstream desktop part. The individual components may have similarities, but the whole cohesive package in which the parts are put together and how they work together is the difference.
From pure raw power PC already is leaps and beyond consoles at this point.
Thing is games need to be first created to use that power. Without it PC will have only IQ advantage which is lame for hardware that is x times powerful.
I think The Witcher 3 should be good comparison since CDPR treat PC as main platform.
You can optimize performance (why would you not?), but you can't optimize for a hardware set on particular when there is an almost infinite range of hardwares on the market (tell me what is 99% of the PC market?).
It is why you have graphical settings on PC, devs let you a little optimize the game for your platform (and to your taste even if it's always an atrocious dilemma).
It is what benefit the most to closed platforms, not coding to the metal bullshittery.
OldAsUrSock
Banned
I was joking.
MidgarBlowedUp
Member
This.
Seems to be the hardest thing to explain to some PC elitists. You can run the game at 4k, enhance the lighting a good bit, and throw in 8k textures if you want, but that isn't going to make the A.I. better, introduce real time cloth animation, or magically remodel geometry that was originally a normal map or simply textured in. These games have to be designed from the ground up to run on lower end hardware.
In a years time when early PS4/Xbone games get dumped over on PC, and run at higher resolutions with more bells and whistles, the PC gamers like myself, can thank consoles for being the target systems.
qa_engineer
Member
Yes. This is why the move to x86 hardware was such a good move for both MS and Sony. Every generation of consoles going forward, assuming there are consoles 7-10 years from, now will be leaps and bounds more powerful and easier to port/develop for as x86 isn't going anywhere for a while. PC games will benefit in the long run.