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[Gamesradar] PS4 Pro is basically two PS4 chips, using one for old games and both for Pro enhancements.

8K views 96 replies 48 participants last post by  Hyoketsu 
#1 ·
Quote:
Speaking to Eurogamer, PS4 architect and really clever person Mark Cerny explains how the GPU (graphics processor unit) is repeated in the PS4 Pro. "We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."

But, stick a Pro game, in and both chips are activated, doubling the GPU's power while the CPU runs at the same rate - something Cerny says is important to ensure compatibility with older games.

There's also a little extra RAM in the PS4 Pro via 1GB of DDR3 (the PS4 and Pro already has 8GB of faster GDDR5). "On a standard model, if you're switching between an application, such as Netflix, and a game, Netflix is still in system memory even when you're playing the game," explains Cerny. "It allows for a very quick swap between applications. Nothing needs to be loaded, it's already in memory." Now, when you do something similar on the PS4 Pro it uses the slower extra 1GB, leaving the faster GDDR5 RAM free.
Did a seperate news article for this because I believe this is the first time we are seeing a Crossfire setup in a console? I might be so wrong of course.

Also it explains the size of PS4 Pro as it is bulkier than the original PS4 itself.

now If the second GPU will only be in effect when there is a pro enhancement in a game, this throws my theory of older games benefiting from PS4 Pro out of the windows. I was hoping a faster console would help with minimum FPS in games but appereantly not.

source
 
#10 ·
It may not be Xfire/SLI, but it sounds very similar.

If it's not, why would you turn off the "mirror" image of the GPU? Either it's a unified GPU or it's not.

I'm no expert, I admit; but it sounds like a dual GPU setup to me.
 
#12 ·
Quote:
Originally Posted by iARDAs View Post

Did a seperate news article for this because I believe this is the first time we are seeing a Crossfire setup in a console? I might be so wrong of course.

Also it explains the size of PS4 Pro as it is bulkier than the original PS4 itself.

now If the second GPU will only be in effect when there is a pro enhancement in a game, this throws my theory of older games benefiting from PS4 Pro out of the windows. I was hoping a faster console would help with minimum FPS in games but appereantly not.
s
source
older titles can still benefit from the pro via patching
 
#13 ·
Quote:
Originally Posted by LancerVI View Post

It may not be Xfire/SLI, but it sounds very similar.

If it's not, why would you turn off the "mirror" image of the GPU? Either it's a unified GPU or it's not.

I'm no expert, I admit; but it sounds like a dual GPU setup to me.
Quote:
"First, we doubled the GPU size by essentially placing it next to a mirrored version of itself, sort of like the wings of a butterfly. That gives us an extremely clean way to support the existing 700 titles," Cerny explains, detailing how the Pro switches into its 'base' compatibility mode. "We just turn off half the GPU and run it at something quite close to the original GPU."

But what about deploying the additional Pro GPU power in base PS4 mode, similar to the Xbox One S? Or even just retaining the 111MHz GPU frequency boost? For Sony, it's all about playing it safe, to ensure that the existing 700 titles just work.

"I've done a number of experiments looking for issues when frequencies vary and... well... [laughs] I think first and foremost, we need everything to work flawlessly. We don't want people to be conscious of any issues that may arise when they move from the standard model to the PS4 Pro."
 
#14 ·
Quote:
Originally Posted by Tojara View Post
So how does this "butterflied" GPU communicate between the halves? What's the intermediary between the two or is there one at all? How is work assigned to the GPU when both "halves" are working? Do both halves have full access to the GDDR5 or is it split between the halves? Is this akin to cores on a CPU?

Sorry if these are stupid questions, I'm genuinely curious to how this will work.
 
#15 ·
I think what's going on is far simpler than cross-fired GPUs or some strange two-side-by-side GPUs on the same die.

Existing GCN cards can be bios flashed to unlock disabled shader clusters, since the architecture is very flexible and modular. With the right hardware access and supporting software, I don't see why a reason you couldn't do that very same thing in real time. I bet when a PS4 Pro game is put in, it just enables the remaining 18 CUs in real time.

Why would you do that? In PS4 Mode, you could powergate the disabled CUs, saving power. Since PS4 game use a relatively low level API optimized for 18 CUs, the games probably couldn't manage the full 36 CUs properly.
 
#16 ·
CFX or not...the article confirms it's multi-GPU
very interesting...I just hope all first-party devs can full take advantage of it and that it'll scale almost linearly.
 
#18 ·
Quote:
Originally Posted by AmericanLoco View Post

I doubt it's crossfire. As mentioned, it's probably some new power gating features that allow it to disable half the GPU.
This is my guess as well, I see no advantage to having two separate chips vs a single large one.

Edit: The guy clearly says they doubled the gpu size, what are people not understanding?

"We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."
Quote:
Originally Posted by twitchyzero View Post

CFX or not...the article confirms it's multi-GPU
very interesting...I just hope all first-party devs can full take advantage of it and that it'll scale almost linearly.
No it doesnt, read it again.
 
#20 ·
If the PS4 Pro has Dual GPU I will not be suprised, however rumours are rumours and this wasn't exactly definitive. Dual GPU costs less and fits with AMD's propaganda. The 1GB of ddr3 is what bothers me.
Quote:
"On a standard model, if you're switching between an application, such as Netflix, and a game, Netflix is still in system memory even when you're playing the game," explains Cerny. "It allows for a very quick swap between applications. Nothing needs to be loaded, it's already in memory." Now, when you do something similar on the PS4 Pro it uses the slower extra 1GB, leaving the faster GDDR5 RAM free.
For some reason they want to keep all of the gddr5 memory clear from applications like netlflix when switching to a game.

Maybe it has something to do with how they "turn off" half the GPU. Sadly I'm not good in reverse-microengineering so I dont know wether its a technical "issue" or going to be a new level in memory hierarchy.

Quote:
Originally Posted by nagle3092 View Post

This is my guess as well, I see no advantage to having two separate chips vs a single large one.

Edit: The guy clearly says they doubled the gpu size, what are people not understanding?

"We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."
Quote:
Originally Posted by twitchyzero View Post

CFX or not...the article confirms it's multi-GPU
very interesting...I just hope all first-party devs can full take advantage of it and that it'll scale almost linearly.
No it doesnt, read it again.
You can't deny that it's strange language, Normally when you double your graphics power you say "We straight up doubled graphics horsepower!" yet, they didn't
Quote:
We doubled the GPU size by essentially placing it next to a mirrored version of itself
This is marketing, they dont promise twice the performance, they promise twice the GPU size. "essentially"

another reason to believe its Dual GPU
Quote:
That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU.
You can't just "Recompile" a game made for single GPU to support dual GPU. This is because the GPU's can't reach each other's lower level cache. (among many things) this makes the older games 100% incompatible. However, turning one GPU off would fix all those issues.

Correlation does not equal causation. However this does certainly correlate with double GPU
 
#21 ·
welp so much for more stable frame rates in older games. I was really hoping it would help GTA and Tomb Raider. Hopefully it does help.
 
#22 ·
Quote:
Originally Posted by nagle3092 View Post

This is my guess as well, I see no advantage to having two separate chips vs a single large one.

Edit: The guy clearly says they doubled the gpu size, what are people not understanding?

"We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."
Smart to double the units inside the GPU instead of adding another chip. Adding another chip (aka Crossfire or Muti-GPU) means more cost,heat,cooling,power.

Playstation 2 did this in a similar way because instead of Graphics Synthesizer + Emotion Engine running native PS1 games.

The I/O processor which does CD/DVD communication was a actual PS1 CPU (MIPS R3000A) but clocked higher (Plus original 2MB EDO DRAM)

The MIPS R3000A plays the role of CPU+GPU for the PS1 and does the exact same thing for the PS2 to give it that perfect compatibility.

We all know overclocking PS1-PS2 (I assume PS3) will result in fast forwarding a game instead of giving it better framerate because games are programmed for the selected speed.

However does this "fast forward" apply to PS4, My answer is NO.

There is no need to "disable" half of the GPU to remain compatibility

PS4 games that suffer from low framerate could be patched to take advantage of this GPU to give it a consistent framerate.
 
#24 ·
Honestly this is bad. All hopes of previous games having higher FPS at 1080p are gone. Now it will depend on a case by case basis with every delevoper doing their own.

Those consoles are literally PC's in a wallet garden yet they can't do basic things such as better GPU > better perfomance. I mean it was optimal since im sure most console games don't even use VSYNC due to the higher input lag and the fact they always aim for either 30 fps or 60 fps.
 
#25 ·
Lame. I was expecting greater performance, graphics, and resolution in "older' PS4 games because of a faster GPU, but that apparently isn't the case anymore if all they're doing is power gating the card to mimic a PS4 regular. Why would they cripple it like this? What's the issue of compatibility here? I don't get it.

So much for Polaris being in the PS4 Pro (but the Xbox will have it or Vega for sure now), or is it because of the Shader count and irely familiar core clock? I see no reason to get a Pro now. Get a Pro, for what? TO only get 1080P 60 fps if you have a 1080p tv WITH games that are "pro optimized" else it's back to 1600x900 for "non pro games"? that's really lame. But, if you have a 4K tv, with "pro optimized" games, you'll get your 30fps I guess.
Quote:
Originally Posted by omari79 View Post

older titles can still benefit from the pro via patching
I think we all know that the devs wouldn't waste time to go back and patch an old game from 2013 or 2014. They won't use resources for that.
 
#26 ·
Quote:
Originally Posted by nagle3092 View Post

This is my guess as well, I see no advantage to having two separate chips vs a single large one.

Edit: The guy clearly says they doubled the gpu size, what are people not understanding?

"We doubled the GPU size by essentially placing it next to a mirrored version of itself. That gives us an extremely clean way to support the existing 700 [PS4] titles. We just turn off half the GPU and run it at something quite close to the original GPU."
No it doesnt, read it again.
they could have made something that is using an interconnect like http://wccftech.com/amd-coherent-interconnect-fabric-gpus-cpus-apus/ o they could use something to link tthe GPUs in the same substrate to work as a single gpu? then just assign tasks of each with the game code(With GPC?)
Quote:
Originally Posted by kd5151 View Post

Custom 7870x2
PS4 was using a Cutdown HD 7870 GCN1 this uses GCN4 with 2304SP
 
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