Update:

Sony has clarified PS4's RAM situation, providing the following statement to Digital Foundry

"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."

Digital Foundry's sources also clarify that the "flexible memory" is 512MB rather than 1GB, so developers are "guaranteed 4.5GB for development and a further 512MB from the flexible pool."Original story follows:

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A new rumor suggests that PlayStation 4 developers will be able to use less than 70% of PlayStation 4’s RAM for games.While Sony’s new console will contain 8GB of DDR5 memory total, Digital Foundry reports that 3.5GB of that space is reserved for the operating system, leaving only 4.5GB available for games. Anonymous sources clarified to Digital Foundry that 1GB of the reserved RAM is available as “flexible memory” and “may be reclaimed from the OS reservation, based on availability,” making 5.5GB potentially accessible.Internal Sony documents suggest that 4.5GB is the “baseline amount of guaranteed memory available” for games, but that the additional 1GB of “flexible memory” can be used by devs to “boost elements of the game” as long as the memory isn’t needed by PlayStation 4’s OS. PS4 dev kits currently contain a “Game Memory Budget Mode” that offers “normal” and “large” options, with normal allowing for 4.5GB of memory usage by games, while “large” boosts that number to 5.25GB.For comparison’s sake, Digital Foundry points out that Xbox One will reserve 3GB of RAM for its operating system, and that both Xbox One and PS4 “allocate two Jaguar CPU cores to the operating system, and what sounds like a disproportionately higher level of RAM than one might expect.” This allocation will likely be used to allow the system to support features such as the live-swapping of games and applications that Sony showed off in its user interface demo in June.For now PlayStation 4’s RAM allocation is unconfirmed, but we’ve reached out to Sony and will update this story with any comment or clarification we receive. Find out more about the PlayStation 4’s specs and features in our PlayStation 4 wiki guide

Andrew Goldfarb is IGN’s news editor. Keep up with pictures of the latest food he’s been eating by following @garfep on Twitter or garfep on IGN.