PlayStation 4 gives up to 5.5GB of RAM to
game developers
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.
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.
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