PlayStation 4 (codename Orbis) technical hardware investigation (news and rumours)

[Deleted member 11852]

Is it even possible to allocate CUs to dedicated, independent jobs?

I don't know but I don't think it's necessary given how Cerny explained it. If your compute job is critical you give it the highest priority and you're guaranteed compute time unless you're flatly prioritising everything. But that's be silly.

EDIT: From the Gamasutra interview:

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 hard- ware 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 re- quests, and then finally properly prioritized relative to the graphics on a moment-by-moment basis."

 

[Shifty Geezer]

...and then there are multiple levels of arbitration in the hard- ware to determine what runs, how it runs, and when it runs, alongside the graphics that's in the system."

That to me says you can't separate any CUs from the graphics system. You can only request jobs to be done and let the system decide when and how they get done. I don't think it's possible to remove 4 CUs from graphics work and have them work on compute only.

 

[Deleted member 11852]

That to me says you can't separate any CUs from the graphics system. You can only request jobs to be done and let the system decide when and how they get done. I don't think it's possible to remove 4 CUs from graphics work and have them work on compute only.

Could be. I can't see what would be gained, other than curiosity/testing, from reserving CUs 0-3 exclusively for asynchronous compute jobs. If CUs 0-3 are idle because no compute jobs are scheduled you don't want them idle if there are pixels to paint.

 

[zupallinere]

14+4 !!!

Hopefully someone will find a game dev saying that they used 15 instead of 14 CUs for graphics to put this too rest

 

[Strange]

I agree that 14+4 should be a bannable offense. Sick of the talk half a year ago when it was debunked and here we are again, back to square one.

 

[mosen]

I agree that 14+4 should be a bannable offense. Sick of the talk half a year ago when it was debunked and here we are again, back to square one.

Who debunked it? I didn't see the discussion at the time. Can you leave me a link?

 

[Strange]

Who debunked it? I didn't see the discussion at the time. Can you leave me a link?

Er... Mark Cerny?

The chip shots probably also show pretty clearly that there's is no differentiation between the CUs.

You'd also probably see from Killzone CPU/GPU profile slides that there are 4 odd CUs if they're really "different".

There's really no hard evidence except for the leaks that really show the existence of any 4 CUs working any differently than the other 14. If anything, the lack of evidence tells us there's nothing differentiating the CUs, and we have every reason to believe that they're not differentiating according to logic.

 

[Shifty Geezer]

Who debunked it? I didn't see the discussion at the time. Can you leave me a link?

How's about Sony's press release from a year ago that describes it as...

...a unified array of 18 compute units, which collectively generate 1.84 Teraflops of processing power that can freely be applied to graphics, simulation tasks, or some mixture of the two.

 

[DavidGraham]

What's this crap about 14+4 CU configuration? PS4's GPU is a regular GCN GPU that is almost 100% similar to a downclocked HD 7870(20CU) with 2CUs fused off producing the 18 CU. The console chip is only slightly different from the PC chip, the differences are limited to some changes in the L2 caches and some extra instructions.

http://www.extremetech.com/extreme/...u-reveals-the-consoles-real-cpu-and-gpu-specs

Maybe sebbi can chime in and put this matter to rest permanently.

 

[betan]

How's about Sony's press release from a year ago that describes it as...

People seem to be discussing two different issues. Hardware limitation claim has been debunked but not necessarily the diminishing marginal returns argument.

 

[mosen]

Er... Mark Cerny?

The chip shots probably also show pretty clearly that there's is no differentiation between the CUs.

You'd also probably see from Killzone CPU/GPU profile slides that there are 4 odd CUs if they're really "different".

There's really no hard evidence except for the leaks that really show the existence of any 4 CUs working any differently than the other 14. If anything, the lack of evidence tells us there's nothing differentiating the CUs, and we have every reason to believe that they're not differentiating according to logic.

Who talked about different CUs? Even in Vgleaks documents there was no mention about different CUs.

How's about Sony's press release from a year ago that describes it as...

They said that all CUs can "freely be applied to graphics, simulation tasks, or some mixture of the two" but what They said doesn't conflict with saying "if you use more than 14CUs for rendering, you will see minor boost".

What's this crap about 14+4 CU configuration? PS4's GPU is a regular GCN GPU that is almost 100% similar to a downclocked HD 7870(20CU) with 2CUs fused off producing the 18 CU. The console chip is only slightly different from the PC chip, the differences are limited to some changes in the L2 caches and some extra instructions.

http://www.extremetech.com/extreme/...u-reveals-the-consoles-real-cpu-and-gpu-specs

Maybe sebbi can chime in and put this matter to rest permanently.

I am not talking about different CUs.

This slide created by Sony and I'm saying what they said (Maybe it's made-up by Vgleaks?!):

http://www.vgleaks.com/playstation-4-balanced-or-unbalanced/

Each CU contains dedicated:
- ALU (32 64-bit operations per cycle)
- Texture Unit
- L1 data cache
- Local data share (LDS)
About 14 + 4 balance:
- 4 additional CUs (410 Gflops) “extra” ALU as resource for compute
- Minor boost if used for rendering

http://www.vgleaks.com/world-exclusive-orbis-unveiled-2/

All CUs are the same but GPU is balanced for 14CUs and those 4 additional CUs (or extra ALUs) can be used for both rendering or GPGPU (and according to Sony some mixture of the two) but using them for rendering will have minor boost. Why you guys deny this slide? This is from same PDF/PPT that talks about ACP:

http://www.vgleaks.com/playstation-4-audio-processor-acp/

And even Cerny said the same thing:

Mark Cerny: That comes from a leak andis not any form of formal evangelisation. The point is the hardware is intentionally not 100 per cent round. It has a little bit more ALU in it than it would if you were thinking strictly about graphics. As a result of that you have an opportunity, you could say an incentivisation, to use that ALU for GPGPU.

But with downplaying the number of ALUs.

 

[Rurouni]

I think most of us knows that the PS4 is a bit ALU heavy. But I personally don't like this talk about 14+4 talk because what probably started (by Sony?) as the recommended usage can be used to create pointless debates about either the 4CUs are different or not. We need to stop talking about it.

 

[Strange]

Who talked about different CUs? Even in Vgleaks documents there was no mention about different CUs.



They said that all CUs can "freely be applied to graphics, simulation tasks, or some mixture of the two" but what They said doesn't conflict with saying "if you use more than 14CUs for rendering, you will see minor boost".



I am not talking about different CUs.

This slide created by Sony and I'm saying what they said (Maybe it's made-up by Vgleaks?!):

http://www.vgleaks.com/playstation-4-balanced-or-unbalanced/

http://www.vgleaks.com/world-exclusive-orbis-unveiled-2/

All CUs are the same but GPU is balanced for 14CUs and those 4 additional CUs (or extra ALUs) can be used for both rendering or GPGPU (and according to Sony some mixture of the two) but using them for rendering will have minor boost. Why you guys deny this slide? This is from same PDF/PPT that talks about ACP:

http://www.vgleaks.com/playstation-4-audio-processor-acp/

And even Cerny said the same thing:

But with downplaying the number of ALUs.

Because you're fundamentally disregarding the need to add any CUs to any AMD GPU.

We have 7850 with 16 CUs, 7870 with 20 CUs. 7950 with 28 CUs. 7970 with 32 CUs.
All of them (as with the PS4) have 32 ROPs.
So please tell us, if PS4 is hitting a cliff @ 14 CUs, what's the reason for AMD to release GPUs in the same series all the way up to 32 CUs?

We might also want to remember that PS4 does indeed outperform a 12 CU machine by quite a large margin.
We have 720p vs 1080p to 720p vs 900p to 900p vs 1080p. In any case, it's hard to imagine that all the resolution/fps differences that we observe today is purely the effect of 2 (14-12) CUs and the other 4 give a minor boost.

The argument of 14+4 where the 4 doesn't do much and is designed for compute is weak in the face of hard evidence.
They may have slapped on an additional 4 CUs just to tweak the balance, but it doesn't change the fact that they're fully functional and we are quite clearly seeing the difference they make.


Moreover, the fact that there is no hardware differentiation between the 14 and the 4 should really be enough to put an end to the argument.
The developers are free to do whatever they like with 18CUs, and I think that's all we really need to know.
Whether they use 1 for compute or 17 for compute is really up to the developers and how they design their game and it shouldn't matter to us at all.


I think we're getting lost here. I don't exactly see your argument and why we're debating 14+4 again.

 

[mosen]

Because you're fundamentally disregarding the need to add any CUs to any AMD GPU.

We have 7850 with 16 CUs, 7870 with 20 CUs. 7950 with 28 CUs. 7970 with 32 CUs.

All of them (as with the PS4) have 32 ROPs.

So please tell us, if PS4 is hitting a cliff @ 14 CUs, what's the reason for AMD to release GPUs in the same series all the way up to 32 CUs?

We might also want to remember that PS4 does indeed outperform a 12 CU machine by quite a large margin.
We have 720p vs 1080p to 720p vs 900p to 900p vs 1080p. In any case, it's hard to imagine that all the resolution/fps differences that we observe today is purely the effect of 2 (14-12) CUs and the other 4 give a minor boost.

The argument of 14+4 where the 4 doesn't do much and is designed for compute is weak in the face of hard evidence.

That 12 CUs machine isn't related to this topic and definitely it has its own problems (eSRAM low space), on the other hand most of the multiplatform games are using the same assets on both platforms to date (I don't know if rendering at higher resolution needs more ALUs or not, or it's only ROPs/Bandwidth/Memory related).

Comparing the PS4's GPU to PC GPUs that are balanced for what they are isn't right thing to do, we don't have enough information about PS4's GPU or PC GPUs to compare them. Sony said that they have balanced PS4 GPU for 14 CUs , or in Cerny term there are more ALUs in PS4 than what they needed if they were only aiming for graphics rendering. I don't know what fact or components makes the PS4 a balanced machine for 14 CUs and I don't know how much that "minor boost" will be, if using those 4 CUs for rendering is what a developers really wants. I have no answer for this questions but these words were came from Sony's mouth unless you want to debunk the reliability of VGleaks which is another story.

I think we're getting lost here. I don't exactly see your argument and why we're debating 14+4 again.

My argument is what I can read on that slide, not what I think or like to think.

Again I'm not talking about different CUs or 14+4, I'm talking about PS4 being balanced at 14CUs for rendering. That is what I can read on Sony slide (not 14+4). Maybe using the term "4 additional CUs" on that PDF/PPT leads to 14+4 idea/wording, I don't know. But I can say that all of those 18CUs are the same and all of them can be used for rendering as they mention on the slide, so no different CU.

 

[Pixel]

That slide says that all 18 have texture units,why would 4 gpgpu only compute units have texture units if they were only for gpgpu, does that not imply that all 18 can be used for 3d rendering?


Lets look at a die shot of the ps4.

Spoiler

 

[Shifty Geezer]

Who talked about different CUs?

The prior page of discussion? The subject arose again because a dev mentioned the '14+4 configuration'. There is no 14+4 configuration. There is only 18 CUs configuarion. How devs choose to use that is down to them. The notion of diminishing returns is tangential to the discussion of PS4's technical hardware investigation. PS4's hardware is 18 CUs that devs can use however they want. The discussion of whether 18 CUs on graphics in PS4 is a wasteful or not belongs to its own thread.

 

[Shortbread]

Strange, just leave it alone. No need to feed into this nonsense any further. The die-shots has/have proven this for the millionth time, that the GPU has 20 compute units total (minus -2 for yield purposes). No separate (4 CUs) sitting outside of the aggregated array or any located in other parts of the PS4 design.

People are going to believe what they want to believe, just leave it at that.

 

[Shifty Geezer]

Strange, just leave it alone. No need to feed into this nonsense any further. The die-shots has/have proven this for the millionth time, that the GPU has 20 compute units total (minus -2 for yield purposes). No separate (4 CUs) sitting outside of the aggregated array or any located in other parts of the PS4 design.

Mosen's not talking about a hardware split. I've alrady mentioned his discussion doesn't belong here. I'll spawn it out.

 

[Megadrive1988]

[this starts out off-topic but my question is specifically about what PS4 is capable of]

So PC Dark Souls II is now out, and for the most part, sounds like the final version is indeed a far better port than PC DS1 was.

Early problems seem mostly with getting the game to start up and such, not performance / resolution. Even those with older PCs that have mid range 2011 ~ 2013 GPUs (even midrange Fermi) have no trouble running it in native 1080p with max settings and no dips.



Now a question for technically minded people familiar with the PlayStation 4 hardware. Just out of pure curiosity, is PS4 is technically capable of running the earlier 2013 DSII build with the more advanced lighting, shadows, greater particle counts, somewhat higher geometry detail in certain places, etc. at 60fps, native 1080p? --Although without the burden of any further upgrades.

As seen here in the TGS 2013 "ACHING BONES" trailer which is 1080p60, all real-time but probably running on PC:

http://www.gamersyde.com/download_dark_souls_ii_tgs_trailer-30829_en.html
http://www.gamersyde.com/stream_dark_souls_ii_tgs_trailer-30829_en.html

There's also a couple gameolay videos of the TGS 2013 demo on PS3 with the great lighting and darkness, but naturally more like 720p 30 FPS.
https://www.youtube.com/watch?v=_v-xM2tzljA
https://www.youtube.com/watch?v=IWI-TRZQpwI


Note:
I do understand the just-released PC version certainly does not bring back the dynamic lighting, the original darkness being nicely lit up just enough to see right in front of you, the additional particle effects and geometry from the early trailers and demos, despite running DSII much better than PS3/360.

I also understand there's no way FROM would add those things back in a version of DSII on PS4 and even a straight port of the existing PC version is probably unlikely to happen.

Just wanted to know if PS4 simply has enough raw performance to run a hypothetical full DSII game of the quality seen in the TGS trailer, at 60fps, or not. I ask specifically about PS4 and not Xbox One given that PS4 has about double the pixel fillrate.

 

[shredenvain]

I am no expert but with proper time and optimizing I think the Ps4 could hit the 1080p 60fps target for DS2. I dont think the Ps4 having double the pixel fillrate would have much to do with it though. The Ps4 would never hit its maximum pixel fillrate in a 3d game because of bandwidth. The 32 rops do provide the Ps4 with fillrate overhead that the Xbox One doesnt have.