What is PS4's 14+4 CU thing all about? *spawn

[Airon]

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


This seems to be the final and official confirmation of the 14+4 CU topic directly from a Sony doc aimed to developers.
The "hardware is balanced at 14 CU", 4 additional CU gives "minor boost if used for rendering".
"4 additional CU extra ALU as a resource for compute".

Obviously developer can use all the 18CU for rendering, but which would be the return in terms of performance as as Sony said that 4CU gives minor boost x rendering?

I have always stated this, the 4 additional CU are there to compensate PS4 CPU, as PS4 seems to lack some dedicated hardware that off-load cpu works. The 4 extra CU will be usefull in that regard.
Also becasue I have a strange feeling regarding Jaguar CPU clock.

 

[Shifty Geezer]

"Copyright 2012." Old news, already discussed when VGLeaks first leaked it and the subsequent ongoing discussion.

 

[Airon]

"Copyright 2012." Old news, already discussed when VGLeaks first leaked it and the subsequent ongoing discussion.

Ok, but it seems to me that we have never get the official confirmation.

 

[Shifty Geezer]

Official confirmation of what?

 

[Michellstar]

Ok, but it seems to me that we have never get the official confirmation.

Straight from the horse´s mouth
http://www.eurogamer.net/articles/digitalfoundry-face-to-face-with-mark-cerny

"Digital Foundry: Going back to GPU compute for a moment, I wouldn't call it a rumour - it was more than that. There was a recommendation - a suggestion? - for 14 cores [GPU compute units] allocated to visuals and four to GPU compute...
Mark Cerny: That comes from a leak and is 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 this is old news...

 

[Airon]

Official confirmation of what?

That 14+4Cu etc... was not invented by VGleaks but it cames directly from a Sony doc for developers.

 

[Shifty Geezer]

That 14+4Cu etc... was not invented by VGleaks but it cames directly from a Sony doc for developers.

VGLeaks source as the developer documents. This is just the slide they saw. We had Cerny talk about the 14+4 description, as Michellstar quotes above.

 

[Strange]

14+4 strikes again. Could we PLEASE stop harping on it?

 

[Airon]

14+4 strikes again. Could we PLEASE stop harping on it?

Sorry, I do not understand.
This is some kind of taboo?
I believed that could be interesting to see that the 14+4 CU come directly from Sony, from one of their doc.
And Cerny, even in his full PR Mode, in a way confirmed it many time.
I thought that this thing were quite important, maybe one of the most important topic.
That is it.

 

[Betanumerical]

Sorry, I do not understand.
This is some kind of taboo?
I believed that could be interesting to see that the 14+4 CU come directly from Sony, from one of their doc.
And Cerny, even in his full PR Mode, in a way confirmed it many time.
I thought that this thing were quite important, maybe one of the most important topic.
That is it.

But it still doesn't make sense to me, how can you have a situation where GPGPU is viable but graphics commands not? it can't be a CPU limited situation unless your moving something from CPU to GPGPU to free it up because GPGPU programs still require some CPU time.

 

[Shortbread]

14+4 strikes again. Could we PLEASE stop harping on it?

LOL.... That's the magic balanced equation PS4 must have to operate correctly. 14CUs for graphics rendering and 4CUs for compute needs. God forbid that the 18CUs are all equally the same, and can be used for any purpose or need, other than supporting a split CU example Cerny mentioned (potential for future compute related tasks). The PS4 is so damn unbalanced...

 

[patsu]

It will depend on the programmers/games. No point limiting them to 14+4. Once the developers understand the weaknesses and strengths of the h/w + s/w runtime, they will tweak their code to hit their performance targets.

People criticized PS3 to be unbalanced too. That didn't stop the first parties.

 

[Shortbread]

It will depend on the programmers/games. No point limiting them to 14+4. Once the developers understand the weaknesses and strengths of the h/w + s/w runtime, they will tweak their code to hit their performance targets.

People criticized PS3 to be unbalanced too. That didn't stop the first parties.

And to piggyback off that, Cerny has mentioned multiple times that there is no launch games using a compute structure yet, which means those 4 lonely CUs must be do something else. Oh wait, they're just doing what the other similar CUs are doing - processing graphic needs.

 

[Rangers]

And to piggyback off that, Cerny has mentioned multiple times that there is no launch games using a compute structure yet, which means those 4 lonely CUs must be do something else. Oh wait, they're just doing what the other similar CUs are doing - processing graphic needs.

At possibly less visual return...(If Sony is to be believed)

 

[Shortbread]

At possibly less visual return...(If Sony is to be believed)

How? By possibly being CPU bound? From what I read/heard from other developers, the Jaguar CPU is quite capable of handling large amounts of throughput. So that leaves system memory and bandwidth allocation, which seems PS4 has enough of - in spades.

 

[patsu]

Nextgen, the visuals can use more compute power to back up their presentation (e.g., physics, ray tracing/casting). It also changes moment to moment. At time t, they may use all CUs for visuals; next moment, the CUs may be reassigned for something else. There is no need to cast them as 14+4 blocks.

If MS use 10% GPU for Kinect, basically, Sony has more to spare too.

 

[Rangers]

How? By possibly being CPU beyond? From what I read/heard from other developers, the Jaguar CPU is quite capable of handling large amounts of throughput. So that leaves system memory and bandwidth allocation, which seems PS4 has enough of - in spades.

Well, evidently Sony, the creators of the system, and evidently the most truthful company around if we compare recent press clippings, disagree...

What's the bottleneck we've discussed to death, it could be beyond the "big ones" of CPU/BW that we discuss. From a layperson like me it certainly wouldn't appear to be BW, comparing to the PC space.

CPU does seem reasonable. If you built a gaming PC with an 8 core Jag at just 1.6 ghz, yeah it'd probably be a problem. Not necessarily analogous to the console space, but if we just looked at PC to decide PS4 isn't BW bound, we can do it for CPU comparison too and possibly get some value.

 

[patsu]

Probably different for different games. I remember the KZ4 demo uses 50% CPU and more on the GPU side, whatever that means. They didn't say CPU is the bottleneck. At launch, they are likely all just feeling around.

I suspect the humans and project constraints (scope, schedule, resources) will limit the games, not the h/w.

 

[Shortbread]

Well, evidently Sony, the creators of the system, and evidently the most truthful company around if we compare recent press clippings, disagree...

XB1/PS4 share the same AMD DNA, except for the modified/enhanced/add-more-here needs for their respective systems. So being the PR media darlings doesn't matter in that respect.

What's the bottleneck we've discussed to death, it could be beyond the "big ones" of CPU/BW that we discuss. From a layperson like me it certainly wouldn't appear to be BW, comparing to the PC space.

CPU does seem reasonable. If you built a gaming PC with an 8 core Jag at just 1.6 ghz, yeah it'd probably be a problem. Not necessarily analogous to the console space, but if we just looked at PC to decide PS4 isn't BW bound, we can do it for CPU comparison too and possibly get some value.

We don't know of any changes/enhancements/clock-speeds/cache-sizes that Sony required for the Jaguar CPU. We just don't know... other than the default info on a standard Jaguar CPU within the PC space. I wouldn't be surprised if the clock-speed is slightly greater than 2GHz, but we just don't know.

 

[Deleted member 7537]

Probably different for different games. I remember the KZ4 demo uses 50% CPU and more on the GPU side, whatever that means. They didn't say CPU is the bottleneck. At launch, they are likely all just feeling around.

I suspect the humans and project constraints (scope, schedule, resources) will limit the games, not the h/w.

This guys don't care about arguments, they just want to prove the performance gap between XB1 and PS4 does not exist.