PS4 PlayStation 4 gives up to 5GB of RAM to game developers

Martok

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UPDATE #2: Sony has issued a statement:

We would like to clear up a misunderstanding regarding our "direct" and "flexible" memory systems. The article states that "flexible" memory is borrowed from the OS, and must be returned when requested - that's not actually the case.

The actual true distinction is that:
  • "Direct Memory" is memory allocated under the traditional video game model, so the game controls all aspects of its allocation
  • "Flexible Memory" is memory managed by the PS4 OS on the game's behalf, and allows games to use some very nice FreeBSD virtual memory functionality. However this memory is 100 per cent the game's memory, and is never used by the OS, and as it is the game's memory it should be easy for every developer to use it.
We have no comment to make on the amount of memory reserved by the system or what it is used for.

Based on this information, plus the new source coming forward to explain the properties of flexible memory, our take on this right now is that there is 4.5GB of conventional RAM available to developers, along with the OS-controlled flexible memory Sony describes, in addition to that.
We understand that this is a 1GB virtual address space, split into two areas - 512MB of on-chip RAM is used (the physical area) and another 512MB is "paged", perhaps like a Windows swap file. But to be clear, of the 8GB of GDDR5 on PS4, our contention is that 5GB of it is available to developers.

The good news is that the amount is static and not dictated by OS functions as we stated in our original post, making it a lot easier for developers to work with.

UPDATE: A new source familiar with the matter has provided additional information to Digital Foundry that confirms only 4.5GB of the PS4's 8GB GDDR5 memory pool is guaranteed to game developers right now, while also clarifying how the PS4's "flexible memory" works in practice.

In real terms, an additional 512MB of physical RAM may be available in addition to the 4.5GB mentioned in the SDK. Flexible memory consists of physical and virtual spaces, and the latter introduces paging issues which impact performance. In our original story we combined them together.

For practical game applications, the correct figures for this story, as we understand it now, are a guaranteed 4.5GB for development and a further 512MB from the flexible pool. We have updated the headline accordingly.

Original story: PlayStation 4 reserves 3.5GB of its 8GB GDDR5 memory for the operating system, leaving 4.5GB of space for game code, according to current PlayStation 4 documentation shown to Digital Foundry by a well-placed development source. However, further sources suggest that an additional 1GB of "flexible memory" may be reclaimed from the OS reservation, based on availability.

Sony's internal docs say that 4.5GB is the baseline amount of guaranteed memory available for game-makers (note the memory usage of the Killzone: Shadow Fall demo) and most likely what the lion's share of launch titles will be using. However, other sources close to Sony indicate that developers can request up to an additional gigabyte of "flexible memory", and use it to boost elements of the game - but only if the background OS can spare it. We're told that incorporating this isn't trivial, and it may well be that to begin with only first-party developers target its usage.

Current PlayStation 4 dev kits have a "Game Memory Budget Mode" in the debug settings featuring two options: normal and large. The normal mode setting confirms that 4.5GB of memory is usable for game applications. The large mode increases this considerably to 5.25GB, but the docs are clear that the extra RAM here is only available for application development, presumably in order to house debugging data. From what we understand, the extra gig of flexible memory appears to work in addition to these allowances.

The news that the PS4's OS reservation is in the same ballpark as Xbox One's equivalent 3GB allocation is sure to surprise many, especially bearing in mind that previously leaked Sony docs have only spoken of a 512MB allocation for the system software - though this information hails from the era where the new PlayStation was slated to ship with only 4GB of memory.


Guerrilla Games developed its own profiling tools for PS4 during the development of Killzone: Shadow Fall. The CPU performance analysis tool is pictured here, strongly suggesting that six of the eight AMD CPU cores are available to developers.


There are many parallels with the Xbox One. Both consoles allocate two Jaguar CPU cores to the operating system, and what sounds like a disproportionately higher level of RAM than one might expect - especially in comparison to PC, where Windows operates perfectly well with less than a gig of memory at its disposal. However, in a world where even the Wii U reserves 50 per cent of its onboard RAM for the operating system, the big bump in PS4's OS allocation is perhaps not completely surprising. The console's leap from 4GB to 8GB has seemingly opened the door for Sony to be much more ambitious about what tasks the PlayStation 4 performs in the background and in parallel with gameplay.

Microsoft has already showcased Xbox One's abilities in this regard, but our sources say that PlayStation 4 is also capable of similar feats, perhaps in a manner more closely resembling that of PS Vita - the game is paused, apps are switched over seamlessly and, once exited, gameplay continues without having to restart the code. The convenience and functionality is undeniable, but it comes at a cost to memory consumption.

As it stands, both next-gen consoles will launch with 8GB of unified memory, but with a significantly diminished amount actually available to games developers. However, a big area of difference between Sony and Microsoft's approaches to OS allocation could come in their future plans for the reserved RAM. A Microsoft insider tells us that the engineers behind the Xbox One specifically chose 3GB in order to allow the background platform to evolve over a ten-year life-cycle - it's very hard to add features if the pool of available RAM is reduced from its initial level. The reserved RAM allocation there is set in stone, and is unlikely to change.

However, sources close to Sony suggest that the PS4 approach is perhaps more flexible - the current allocation in terms of both CPU cores and memory could be reduced once the operating system is complete and then streamlined. In short, while there is no guarantee of change in the future, Sony is at least leaving the door open to the opportunity and the R&D team has experience in reducing the OS footprint - just as it did on PlayStation 3.

In the here and now, the template is now set for the next-gen launch period, and the focus from both platform holders is that while games command the majority of system resources, supplementary services and apps are clearly very important indeed. Microsoft has already set out its stall in this regard - now it remains to be seen what additional features PlayStation 4 brings to the table above and beyond its core gaming functions.

Source: CVG
 

ColSonders

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That's a very well written piece considering it is based on pure speculation.

They've taken the figure that Microsoft have said is required by the OS and assumed that PS4 will be about the same, then written a story to fit that....well done.

In reality, none of these figures have been confirmed by Sony and whilst a lot of the guesswork is probably correct, Sony have a lot of chips in the PS4 to handle specific tasks such as background downloading and always recording/encoding video, so these processes will likely take far less memory than the equivalent process on XBOX. Also bear in mind that Microsoft is probably the worst known company in history when it comes to memory management, it's most recent version of Windows is still an utter pile of shit that uses far too much memory for it's performance levels and has only recently started utilising spare memory well enough to make an impact at all on performance.

I'm confident that Sony can deliver the goods in terms of a lightweight and secure OS for their new machine, i'm far more concerned about the layout of the OS and the implied functionality with the trend in flashy OS's that are designed for ****ing touch screens and then wedged onto full fledged machine that doesn't even have a touch screen.

edit * I also seriously doubt that the XBox spec in terms of pre-assigned memory is as set in stone as this article makes out, as I mentioned I have no faith at all in Microsofts ability to streamline an operating system (and they're running 3 from what i've heard on Xbox180). What they do have and will no doubt rely on though is the cloud service, OS functions will no doubt be moved to the cloud later in the XBox180's life once they can define which OS functions are only utilised during online gameplay. That's not to say Sony can't also do this, I just don't think they will.
 

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Whichever way you slice it , it looks like a larger and larger proportion of the money you pay for a machine is spent suporting flashy features that you will probably never use. I would rather the minimum amount of overheads is available for the OS and the rest available for games, but I suppose we have to have something these days for the self obsessed social crowd to post OMG videos of themselves being arses in Call of Duty.
 

ColSonders

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I think it's the general responsiveness of the system that is going to eat into that memory, the PS3 has been a fantastic system, but the constant waiting for things to load is a royal pain in the backside.

Trophy syncing is horrible for me, I imagine for those with a lot more trophies it's far worse, the fact that it can't background download/install a good many things can be annoying depending on what you're playing.

The PSN Store is disgustingly slow, which I know is taking data off the interwebs, but that data could be partially cached.

These issues are all being dealt with from what I gather on the PS4 and had they not done this then the system wouldn't sell.

As much as a lot of the features won't be used by many, I think there's probably a lot of small features that will really improve the overall experience on these next gen systems and i'm grateful of it.

Plus i'm positive that there's plenty of memory there for games....given the better GPU's on PC's have 6GB of RAM and they're only really required if running multiple monitors at silly resolutions I think we should be just fine for a long time to come.....and who knows, Sony may even allocate less memory to the OS at a later date or as Microsoft will likely do, offload less time sensitive tasks to a cloud service.
 

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Ive read this too. I try to stay away from all the willy waving by Microsoft and Sony, but this, if true, is actually a positive thing. I remember all the new system updates for the 360. It wasn't amended, it was completely revolutionised. The NXE release was like having a new console under the telly, it really was. The xmb is starting to look really stale now. Sony said it wasnt possible to do what Microsoft did to the 360 because of RAM restrictions. So I'm happy they're future proofing my console for me.
 
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