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PS4's memory subsystem has separate buses for CPU (20Gb/s) and GPU(176Gb/s)

A

androvsky

Member
Well, we know the PS3 has 6 SPUs available to developers with one reserved for the OS (i.e., security) and one disabled, right? I remembered that it seemed like GG had a PDF that showed Killzone 2 only using 4 SPUs, and I decided to dig it up.
http://www.guerrilla-games.com/publications/dr_kz2_rsx_dev07.pdf
Starts on page 45, shows usage for 4 SPUs and the PPU. What are the other two doing? Dunno. Game AI and Physics are shown to be on the PPU. There's definitely audio happening somewhere in there, but I'd be surprised if it took both SPUs unless it's something like encoding DTS 7.1. Even the Edge tools Cell geometry acceleration is accounted for, unless "edgeGeom" is something else.

So no, we can't assume there's two cores reserved for the OS because a Guerrilla Games PDF doesn't show usage for two of the cores.
 
A

alexandros

Banned
This thread has been highly educating, I feel I have a (bit) better understanding of the technology involved. Still wish I had the necessary knowledge to understand it fully :(
 
N

NBtoaster

Member
androvsky said:
Well, we know the PS3 has 6 SPUs available to developers with one reserved for the OS (i.e., security) and one disabled, right? I remembered that it seemed like GG had a PDF that showed Killzone 2 only using 4 SPUs, and I decided to dig it up.
http://www.guerrilla-games.com/publications/dr_kz2_rsx_dev07.pdf
Starts on page 45, shows usage for 4 SPUs and the PPU. What are the other two doing? Dunno. Game AI and Physics are shown to be on the PPU. There's definitely audio happening somewhere in there, but I'd be surprised if it took both SPUs unless it's something like encoding DTS 7.1. Even the Edge tools Cell geometry acceleration is accounted for, unless "edgeGeom" is something else.

So no, we can't assume there's two cores reserved for the OS because a Guerrilla Games PDF doesn't show usage for two of the cores.
Click to expand...

Well it was the case that the OS could also steal part of a second SPU so you couldn't rely on it.

That slide is also from almost 2 years before the game came out, using all the SPUs in 2007 was rare.
 
A

androvsky

Member
NBtoaster said:
Well it was the case that the OS could also steal part of a second SPU so you couldn't rely on it.

That slide is also from almost 2 years before the game came out, using all the SPUs in 2007 was rare.
Click to expand...

Ah, I'd forgotten about the OS stealing an SPU, but that still leaves one unaccounted for. I recall using any SPUs back then was kind of a big deal, using 5 probably wasn't much harder than 4. And now they're dealing with a launch system with all the uncertainties that entails.
 
U

Unknown Soldier

Member
I2amza said:
There is no way the OS is not using anything. Unless the system has another source for the OS to get memory, it has to get it from the main memory which is the GDDR5.
Click to expand...

On Windows machines, unused portions of the OS are paged out of main memory when not being used. This used to matter in the days when PCs actually had a limited amount of RAM, you could grind the old Windows machines to a halt by forcing too much memory paging. Nowadays your average PC has 8 GB of RAM and Windows never gets paged to disk.

On the PS4, it's not hard to imagine that the OS has a state which uses more memory when a game isn't running, and a state which uses less memory when a game is running. This isn't 180 where it's running 3 OSes at once to enable TV, SPORTS, and CALLADOODY. I doubt the PS4 needs that much OS-related stuff running all the time when it's playing a game and stuff that isn't needed can be kicked out when the game demands it.
 
M

maplelord93

Banned
Unknown Soldier said:
On Windows machines, unused portions of the OS are paged out of main memory when not being used. This used to matter in the days when PCs actually had a limited amount of RAM, you could grind the old Windows machines to a halt by forcing too much memory paging. Nowadays your average PC has 8 GB of RAM and Windows never gets paged to disk.

On the PS4, it's not hard to imagine that the OS has a state which uses more memory when a game isn't running, and a state which uses less memory when a game is running. This isn't 180 where it's running 3 OSes at once to enable TV, SPORTS, and CALLADOODY. I doubt the PS4 needs that much OS-related stuff running all the time when it's playing a game and stuff that isn't needed can be kicked out when the game demands it.
Click to expand...
I think Sony did that with the Vita OS.
 
I

I2amza

Member
Unknown Soldier said:
On Windows machines, unused portions of the OS are paged out of main memory when not being used. This used to matter in the days when PCs actually had a limited amount of RAM, you could grind the old Windows machines to a halt by forcing too much memory paging. Nowadays your average PC has 8 GB of RAM and Windows never gets paged to disk.

On the PS4, it's not hard to imagine that the OS has a state which uses more memory when a game isn't running, and a state which uses less memory when a game is running. This isn't 180 where it's running 3 OSes at once to enable TV, SPORTS, and CALLADOODY. I doubt the PS4 needs that much OS-related stuff running all the time when it's playing a game and stuff that isn't needed can be kicked out when the game demands it.
Click to expand...

I could see that happening. It's practically what's happening on the Vita right now. The OS shrinks and expands. But I still don't see the need of paging from memory when you have such a hearty amount of RAM.
Also I am afraid that paging out to the disk will cause the OS to feel clunky due to the speed differences between RAM and HDD.
 
staticneuron

staticneuron

Member
i-Lo said:
Unless I'm missing something, there is no such confirmation in that article.
Click to expand...

The GPU will also be able to run arbitrary code, allowing developers to run hundreds or thousands of parallelized tasks with full access to the system's 8GB of unified memory.[/QUOTE

It doesn't let us know where the OS resides if true.
Click to expand...
 
C

ConteZero76

Member
I2amza said:
I could see that happening. It's practically what's happening on the Vita right now. The OS shrinks and expands. But I still don't see the need of paging from memory when you have such a hearty amount of RAM.
Also I am afraid that paging out to the disk will cause the OS to feel clunky due to the speed differences between RAM and HDD.
Click to expand...

In exchange they could "swap out" the entire game; having enough HDD space they could let you swap between 2+ games, pausing one to play the other.
 
I

Ironmanxrs2

Banned
The PS4 GPU and access to it appears to be really good. CPU bandwidth appears to be a potential future bottleneck judging from the source article. It will be interesting to see how Sony's coding language will compare to DirectX11.2, especially since PC will be lead development platform for many multiplats.

Did Sony and MS short change the role of the CPU this gen? Was it a sacrifice to going APU with die sizes?
 
I

IN&OUT

Banned
Ironmanxrs2 said:
The PS4 GPU and access to it appears to be really good. CPU bandwidth appears to be a potential future bottleneck judging from the source article. It will be interesting to see how Sony's coding language will compare to DirectX11.2, especially since PC will be lead development platform for many multiplats.

Did Sony and MS short change the role of the CPU this gen? Was it a sacrifice to going APU with die sizes?
Click to expand...

Mark Cerny answer to the bolded part: (Taken from Gamasutra interview in April)

" 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!"
 
I

Ironmanxrs2

Banned
W!CKED said:
The article says that PC is lead platform at the moment because studios had to work with approximation hardware of next gen consoles:

"It makes sense that PC takes centre-stage during the development effort, simply because games take upwards of two years to develop and actual console hardware wasn't available until very recently."

We can expect this situation to change very quickly in favor of the new consoles as soon as final SDKs are available.
Click to expand...

You are probably right. I wonder how that will be split. I'm guessing the big developers have built custom engines that leverage bot efficiently. Frostbite, Unreal4, etc.
 
I

Ironmanxrs2

Banned
W!CKED said:
Much more importantly: The PCIe bus kills your latency. The Onion bus has higher bandwidth, lower latency and is coherent.



3rd-Parties will most likely streamline the multiplatform development. The most profit-yielding approach will win.
Click to expand...

It certainly appears that porting will be much cheaper and easier this gen. We're already seeing some outsourcing by the bigger devs. Wonder if the asset development is more expensive now or if they'll just be more profitable.
 
I

I2amza

Member
Ironmanxrs2 said:
The PS4 GPU and access to it appears to be really good. CPU bandwidth appears to be a potential future bottleneck judging from the source article. It will be interesting to see how Sony's coding language will compare to DirectX11.2, especially since PC will be lead development platform for many multiplats.

Did Sony and MS short change the role of the CPU this gen? Was it a sacrifice to going APU with die sizes?
Click to expand...

Maybe that's also why Cerny said a shift to GPGPU computing for later years. Just have the CPU do some job queuing for the GPU to compute while also doing minor jobs itself.
 
M

mrklaw

MrArseFace
Famassu said:
Sony wouldn't add 4GB more RAM just to futureproof their OS by giving 2 of those 4GBs to OS. That's just silly talk. It makes absolutely no sense for a single OS system like PS4 and would be a completely overboard decision. In no scenario would their OS require 2GBs more RAM.
Click to expand...

The only scenario i can think of appears to be Xbox fans trying to justify xbox's use of 3GB.
 
K

Krilekk

Banned
It's so obvious that the PS Eye has one core dedicated to it. I mean the system was built around it just like Kinect, just look at the controller. They scrapped it late to make the price but of course it still needs dedicated CPU power for those that buy it. So one core for OS, one for Eye. The rest for games.
 
S

Soi-Fong

Member
Krilekk said:
It's so obvious that the PS Eye has one core dedicated to it. I mean the system was built around it just like Kinect, just look at the controller. They scrapped it late to make the price but of course it still needs dedicated CPU power for those that buy it. So one core for OS, one for Eye. The rest for games.
Click to expand...

lol Keep dreaming.
 
B

benny_a

extra source of jiggaflops
Krilekk said:
It's so obvious that the PS Eye has one core dedicated to it. I mean the system was built around it just like Kinect, just look at the controller. They scrapped it late to make the price but of course it still needs dedicated CPU power for those that buy it. So one core for OS, one for Eye. The rest for games.
Click to expand...
wtf.gif
 
B

bassman2112

Member
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
 
N

nib95

Banned
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering
Click to expand...

If true, people would go nuts. Atlantis is the one many of us including me have been asking for. This actually is in line with Hip Hop Gamers rumour that the game starts out in the stormy sea. One can dream.

Reckon it's fake though.
 
S

stryke

Member
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
Click to expand...

Camera angles make these look eerily familiar to the fake "leaked" photos pre E3 (the ones that had tiles of to be announced games).
 
I

I2amza

Member
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
Click to expand...

Hmmm.. He says he will be working on it...
 
V

vazel

Banned
I told myself I wasn't going to buy UC4 after the shitfest that was UC3 but for Atlantis I'm there.

Edit: Yea this is most assuredly fake. Fakes lately have parts of the image cropped. It's like they think that makes it more believable. Like some dude is sneaking in a shot with his cellphone while everyone else in the room isn't watching. You'd think Sony would have people dedicated to making sure no one sneaks in a pic.
 
D

DJwest

Member
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
Click to expand...

I hope its real. Come on ND, lauch Uncharted PS4 game pls.
 
K

kartu

Banned
So it was told that mem controllers on GPUs favor bandwidth over latency, CPU controllers latency over bandwidth. (that's where the myth about GDDR5 having high latency came from, till now only GPUs were using it)

So having two different buses makes perfect sense, provided onion beats garlic on latency.

What puzzles me is that there is a choice which bus to use... Isn't that a bit too low level? Does AMD64 instruction set really allow you to say "I want to access block bla, use bus blabla to access it"? Yikes...

2 cores reserved for OS sounds disappointing... OK you gotta encode stuff for that "share" button to work, but 25% of CPU resources being reserved just for it? =/

And 2Gb reserved for OS, which is HALF of the originally planned 4Gb, isn't it way too much?
 
H

hackdog

Banned
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
Click to expand...

I want to believe...
 
K

kitch9

Banned
Ironmanxrs2 said:
The PS4 GPU and access to it appears to be really good. CPU bandwidth appears to be a potential future bottleneck judging from the source article. It will be interesting to see how Sony's coding language will compare to DirectX11.2, especially since PC will be lead development platform for many multiplats.

Did Sony and MS short change the role of the CPU this gen? Was it a sacrifice to going APU with die sizes?
Click to expand...

20GBs for the CPU is ample, my 3770K gets a lot less than that FFS,
 
K

kitch9

Banned
Krilekk said:
It's so obvious that the PS Eye has one core dedicated to it. I mean the system was built around it just like Kinect, just look at the controller. They scrapped it late to make the price but of course it still needs dedicated CPU power for those that buy it. So one core for OS, one for Eye. The rest for games.
Click to expand...

This is the thread where tard just keeps arriving.
 
P

Perkel

Banned
bassman2112 said:
I apologize because this is completely unrelated to the topic at hand; but could someone create a new thread for me? (Junior Member, et cetera)

According to this Reddit post, there are some Uncharted 4 Leaked Images for a reveal at the VGAs.

Thanks, and carry on with the bickering

Edit: To be fair, I personally think it's fake; but I'm just posting it in case it hasn't been seen.
Click to expand...

Dude it is 2013 not 2003.

Not getting clear picture says that this is fake.
 
L

lightchris

Member
kartu said:
What puzzles me is that there is a choice which bus to use... Isn't that a bit too low level?
Click to expand...

I don't imagine it works that way. Should be automatically selected by the hardware, such that memory requests in CPU code will naturally go through the CPU bus.

edit:
Sorry, didn't really read what this was about.
 
T

TheD

The Detective
Unknown Soldier said:
On Windows machines, unused portions of the OS are paged out of main memory when not being used. This used to matter in the days when PCs actually had a limited amount of RAM, you could grind the old Windows machines to a halt by forcing too much memory paging. Nowadays your average PC has 8 GB of RAM and Windows never gets paged to disk.

On the PS4, it's not hard to imagine that the OS has a state which uses more memory when a game isn't running, and a state which uses less memory when a game is running. This isn't 180 where it's running 3 OSes at once to enable TV, SPORTS, and CALLADOODY. I doubt the PS4 needs that much OS-related stuff running all the time when it's playing a game and stuff that isn't needed can be kicked out when the game demands it.
Click to expand...

Alebelly said:
And devs have access to all 8gb

http://arstechnica.com/gaming/2013/...4s-hardware-power-controller-features-at-gdc/
Click to expand...


Programs are not paged out willingly, you always want programs (including the OS) in RAM.
If you paged out the OS to RAM anytime the game wanted to use a system service the system would grind to a crawl and switching into the console's main menu would take ages.

So no, games will never have the full 8GB to use.
 
D

DBT85

Member
kartu said:
2 cores reserved for OS sounds disappointing... OK you gotta encode stuff for that "share" button to work, but 25% of CPU resources being reserved just for it? =/

And 2Gb reserved for OS, which is HALF of the originally planned 4Gb, isn't it way too much?
Click to expand...

The 2 cores is still only being taken from the Shadowfall slides, it's not been confirmed anywhere at all.

Regarding the video encoding however, there is dedicated hardware that will handle that, it won't be being done on one of the CPU cores. I recall a post talking about cores reserved for the OS some time ago and GopherD stating "less than one". Now things might have changed, or his info might be off, but he is very reliable. It's also possible of course that they only need half a core for the OS, but are walling off 2 for example for future expansion.

As for the OS footprint, if it was indeed 512MB with the original 4GB, I doubt they put in 8GB just to make it 2GB for the OS. If they ARE going for 2GB they could well just be going way overboard on reserved OS space which they can lower over the systems lifetime. However if they had wanted 2GB for the OS in the first place the system would have been designed with that in mind from the beginning, like the XBONE being designed to have 8GB from the start.

I expect the PS4 OS to have 1GB walled off and for them to not be using it all come launch day. Maybe they'll lower the walled space maybe they will just keep adding stuff.

The key is that you can never increase the CPU/RAM maximum spaces once the system launches, as old games will not work. You can only decrease the need for either.
 
R

rdrr gnr

Member
nib95 said:
If true, people would go nuts. Atlantis is the one many of us including me have been asking for. This actually is in line with Hip Hop Gamers rumour that the game starts out in the stormy sea. One can dream.

Reckon it's fake though.
Click to expand...

vazel said:
I told myself I wasn't going to buy UC4 after the shitfest that was UC3 but for Atlantis I'm there.

Edit: Yea this is most assuredly fake. Fakes lately have parts of the image cropped. It's like they think that makes it more believable. Like some dude is sneaking in a shot with his cellphone while everyone else in the room isn't watching. You'd think Sony would have people dedicated to making sure no one sneaks in a pic.
Click to expand...
A bit OT, but what exactly is Atlantis for you guys? There have been so many takes on Atlantis (Uncharted 3, technically, so we know this is fake) but the name alone means almost nothing.
 
T

travisbickle

Member
Krilekk said:
It's so obvious that the PS Eye has one core dedicated to it. I mean the system was built around it just like Kinect, just look at the controller. They scrapped it late to make the price but of course it still needs dedicated CPU power for those that buy it. So one core for OS, one for Eye. The rest for games.
Click to expand...


I'm sure they can free up that core now they have changed policy on the mandatory pseye. It might have to be a day one patch though!
 
E

EvB

Member
That same article mentioned that 2CPU clusters are reserved for the OS, has this been mentioned before?
 
D

DBT85

Member
EvB said:
That same article mentioned that 2CPU clusters are reserved for the OS, has this been mentioned before?
Click to expand...

That was mentioned by Eurogamer, not by Reflections. Its the same information that was taken from the Killzone slides.
 
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