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

[Shifty Geezer]

The best point you made, though, is that they can always reduce the amount of reserved RAM during the console's life cycle, while taking away RAM from games that have already been relased is practically impossible. So yeah. But I still think 2GB of reserved RAM would be a really, really much.

7GBs of RAM for a game is also really, really much. reserving 2 GBs for now, having games that have been targeting 3.5 GBs for PS4 for months and 5 GBs on XB1 use 6 GBs for launch, is still going to be generous for developers. They're not going to be hitting a RAM wall early on. Then Sony can reconsider. PS3's OS RAM was pretty halved I believe, but then Sony claimed they hadn't enough RAM to implement cross-game voice chat.

 

[Cjail]

Summary of the 2 most plausible scenarios.

1) Sony original OS reservation (512MB) is unchanged.
The 4 extra GB are just for games as requested by developers and that is why they have publicly expressed their satisfaction for the upgrade
Recent revelations suggest that upgrade to 8GB of ram was not directed by the need to give OS more memory.
Killzone Shadow Fall postmortem gave us hint of who much memory GG used for the demo but they didn't say that it's all the memory they have access to and we even know the code was incomplete and/or running on prototype hardware.
This is actually what GG said about 8GB: "Well, some of that memory is used by the PS4 itself for other purposes. But we will make full use of the RAM available to us!" (source)

2)Sony increased the OS reservation after the upgrade to 8GB because they need/wanted it.
Why Sony needed/wanted more more for the OS is hard to tell and we can just make guesses.
Richard Letterhead has though heard form developers that the OS is at 1GB but he says it's unconfirmed.

Whether more/less RAM available for games is good or not it's debatable.
Devs apparently are aware of the final OS reservation and their lips are sealed or they don't' speak clearly about it.

 

[Cjail]

Double post sorry.

 

[Kb-Smoker]

Given blow comment on twitter and on gaint bomb I would say 1GB is confirmed. This goes with information we already know from Richard also.

 

[itsmydamnation]

yes i really didn't get why people thought sony would spend a whole pile of money going from 4 to 8 gb just to reserve 3gb of it....... it makes no sense. MS on the other hand has much cheaper DDR3 and thus the cost of that reservation in terms of BOM is far lower.

 

[Rockster]

Although Richard suggests that there may be an additional 1GB for game DVR on top of the OS reservation, so I don't think there is enough info to definitely say what it is. Sounds like it has been locked down though, and hopefully that will leak for more certainty.

 

[Cjail]

^^^
He though "counters" that theory saying: "15 minutes of 1080p h.264 video could swallow up anything up to 1GB of RAM, but some might say that it would be something of a waste to utilise high performance memory on an application like this that would require at most around 2MB/s of bandwidth (PS4 GDDR5 tops out at 176GB/s)"

 

[Kb-Smoker]

Although Richard suggests that there may be an additional 1GB for game DVR on top of the OS reservation, so I don't think there is enough info to definitely say what it is. Sounds like it has been locked down though, and hopefully that will leak for more certainty.

That would be a terrible waste of ram. Given the low BW needed for this task and having a HDD drive install in every box. Guess sony is know for making poor OS maybe it does work that way.

 

[betan]

^^^
He though "counters" that theory saying: "15 minutes of 1080p h.264 video could swallow up anything up to 1GB of RAM, but some might say that it would be something of a waste to utilise high performance memory on an application like this that would require at most around 2MB/s of bandwidth (PS4 GDDR5 tops out at 176GB/s)"

That would be a terrible waste of ram. Given the low BW needed for this task and having a HDD drive install in every box. Guess sony is know for making poor OS maybe it does work that way.

To-HDD-BW for 1GiB 15-min properly indexed mp4 video is just 1.4 MiB/s. So yes it would be stupid for Sony to reserve that much ram.

 

[Betanumerical]

Whilst its a good idea to stream to the HDD don't forget that unless the stream buffer for the video is physically close to the game buffer on the platter that you will have a latency penalty every time you have to switch from writing one to reading the other.

 

[Kb-Smoker]

Whilst its a good idea to stream to the HDD don't forget that unless the stream buffer for the video is physically close to the game buffer on the platter that you will have a latency penalty every time you have to switch from writing one to reading the other.

I'm sure there has to be some type of buffer just to process the video file.

 

[Betanumerical]

I'm sure there has to be some type of buffer just to process the video file.

Its probably being worked on by the VCE encoding hardware that is present on modern AMD GPU's, so its going straight to RAM not touching HDD till its encoded.

 

[betan]

Whilst its a good idea to stream to the HDD don't forget that unless the stream buffer for the video is physically close to the game buffer on the platter that you will have a latency penalty every time you have to switch from writing one to reading the other.

I don't know much about BSD but I find that Linux' memory/disk combo management exceptionally good compared to Windows OS. Of course they can always "manually" schedule IO tasks with appropriately sized buffers.

 

[dumbo11]

I'm sure there has to be some type of buffer just to process the video file.

If you write buffered, then logically you start to create slightly bigger 'gaps' where the game cannot access the disk?

Frequent micro-stutter vs delayed 'macro-stutter'.

Personally, I'd just reserve the RAM (it's not like the system really needs it all anyway).

 

[Shifty Geezer]

If you write buffered, then logically you start to create slightly bigger 'gaps' where the game cannot access the disk?

Yes. You wouldn't want the streams to be too large or the game will have significant moments of no access to HDD data. Although with a decent cache, that might not be too much of an issue?

 

[Gubbi]

Mechanical harddrive performance is dominated by seek times. You want to write a video stream in one MB chunks or larger to minimize seeks.

Cheers

 

[zupallinere]

Sounds like the performance characteristics of GDDR5. Are textures "swizzled" on the HD as well ?

 

[Cjail]

15' anyway would not have fit when the OS was at 512MB so either PS4 could record less than 15' and then write them to RAM before the upgrade or Sony never choose write to RAM in the firs place.

 

[Kb-Smoker]

Its probably being worked on by the VCE encoding hardware that is present on modern AMD GPU's, so its going straight to RAM not touching HDD till its encoded.

I thought this would be handle by the custom southbridge chip amd/sony design for the PS4

 

[metacore]

How about flash memory for video streaming and other tasks. they could solder 4GB or so , simple , will not bother HDD and its gaming tasks etc. They probably have some for those background updates in low power mode.