In the wake of Sony's confirmation of the PlayStation 4K Neo's existence, we thought we would re-publish this Digital Foundry article, outlining how the original PS4 and the new model will co-exist. This article is based on guidance given out to developers, and it is still current, to the best of our knowledge.

In the wake of the PlayStation 4K 'Neo' leak and the subsequent confirmation, there are still plenty of questions that need answering, and we're intent on bringing you everything we can about the new hardware and especially what it means for owners of the existing PS4.

In this article, we'll be drawing on the rules of engagement that Sony has supplied to PlayStation 4 developers. While these guidelines may change, the picture painted is clear and unambiguous. As the platform holder says explicitly, PS4 and Neo 'co-exist in the marketplace' - one is simply a more technologically capable version of the other, but there are some key points here amongst the wealth of information we'd really like to highlight:

Dual Shock 4 remains the primary controller: Sony has no plans to introduce a new joypad for the Neo hardware. The Dual Shock 4 remains unchanged and Sony has actually mandated that all existing peripherals should be supported with no segregation between PS4 and Neo.

1080p is the mandatory minimum display resolution: Sony is keen to push developers on to higher resolutions and super-sampling down to full HD is an option, but 1080p is the lowest pixel-count allowed.

No online segregation between consoles: If a PlayStation title supports online features, they must be deployed equally on both systems. Developers cannot have Neo-only servers. We believe this may actually introduce gameplay balance issues if, say, the Neo version hits 60fps while the PS4 version is capped at 30fps.

Save data systems are cross-platform: The PlayStation operating system is constant between both PS4 and Neo. This means that all data (save games, back-ups etc) are interchangeable between both systems by default. However, it seems that Sony is leaving it up to developers to ensure that Neo and PS4 save-swapping actually works.

Forward compatibility patches are for old games only: Sony really wants Neo support on all games from October onwards. While older titles can have Neo features patched in, the platform holder will not allow new titles to add Neo features at a later date.

This content is hosted on an external platform, which will only display it if you accept targeting cookies. Please enable cookies to view. Manage cookie settings Rich outlines new PlayStation Neo information, including how the system will live side-by-side with existing PS4.

So those are the headlines, but for those with an eye for detail, here's what we believe is the complete list of rules and guidelines issued to developers. The situation may change, but for now it offers an intriguing insight into Sony's strategy for allowing two different PlayStations to co-exist in the same ecosystem.

PS4/Neo system software functions The PS4 front-end offers an identical experience whether you're running on Neo or an original PS4 system. The PlayStation Store will be exactly the same, but Sony is considering offering enhanced media facilities - for example, 1080p gameplay streaming and recording. Access to 4K media apps with HDCP 2.2 requirements aren't covered in Sony's documentation. In terms of games though, the platform holder is highly detailed in how this is going to work: The same PSN ID can be used to access the same content across multiple PS4 and Neo consoles.

However, you can only have one device allocated as the Primary Console.

The same PSN ID can't be logged in simultaneously on more than one PS4, Neo or combination of the two (presumably the Primary Console can play digital content offline though, as is the case now).

Save games should be interchangeable between PS4 and Neo titles (via USB or cloud storage). However, the system is platform agnostic. Sony is leaving it to developers to ensure this feature works.

Backed up data is interchangeable between Neo and PS4. That is, you can back-up data on either console and restore it with no problems.

Themes and avatars work on both systems.

Developers are not allowed to segregate Neo and PS4 users on the PlayStation Network. Online game modes must offer the same feature set.

Trophies and unlock rules must be totally identical.

PlayStation Store pages and physical game-packaging are expected to list Neo-specific features.

There are no plans to prioritise PS4 or Neo content in using the PlayGo 'fast start' download system. Trophies must be entirely consistent between PS4 and Neo modes, based on Sony's guidelines. There will be no Neo-exclusive trophies or any variance in how they are triggered.

PlayStation 4/Neo Game Compatibility Sony is very keen on developers supporting both systems simultaneously, and is motivating developers to ensure that there is Neo support in all PS4 titles from Q4 onwards this year. It's also firm on unifying the platforms with little or no exceptions: Neo-only or PS4-only games are not permitted (remember that Neo can still run unenhanced titles - developers are simply prohibited from locking out audiences of either console).

All games you purchase, whether via disc or from the PlayStation Store, should offer both PS4 and Neo functionality with no extra costs associated in running titles on a different console.

All new titles with Neo support use unified packages that run on both platforms. The CPU binary is identical, while three GPU binaries (shared, PS4-specific and Neo-specific) are all contained in the same package.

All DLC and additional content is entirely cross-platform. Unified downloads are used for both this, and basic game patches.

Neo support for old games is allowed via 'forward compatibility' patching - but this will not be allowed for new titles.

Developers cannot supply exclusive gameplay features for Neo owners. If the game has a split-screen mode, it must be available on both systems. However, modes can be enhanced - so a two-player split-screen mode on PS4 could be expanded to allow a four-player variant on Neo.

Developers cannot add exclusive content to either PS4 or Neo systems.

If there's a bug in Neo-specific code, developers are not allowed to divert Neo owners to the PS4 codepath. The game must be fixed. Sony says that the front-end experience and the PlayStation Store will be identical on both PS4 and Neo, though Neo-specific features will be listed on product pages.

Peripheral support Sony isn't looking to make any dramatic changes here. We can assume that the Neo hardware has the same primary interfaces here as PS4 - namely, USB 3.0, Bluetooth and the camera interface. The existing Dual Shock 4 is confirmed as the primary interface for Neo. There will be no new controller. As is the case right now, DS4 pads can be used and paired interchangeably between different PlayStation hardware.

Any special game peripheral you have which is compatible with PS4 should run identically on Neo.

There must be no difference in peripheral support between Neo and PS4 versions.

Rendering guidelines We've already described how Sony is looking to offer higher resolution support for 4K screens with the Neo hardware, and how higher frame-rates, more stable frame-rates, improved graphics fidelity and further visual features are encouraged. It's a topic we'll be returning to in due course as more information comes in. However, In terms of hard and fast technical guidelines for Neo rendering, Sony offers this: Games running in Neo mode must operate at a native rendering resolution of 1920x1080 (1080p) or higher.

A game's frame-rate must meet or exceed its equivalent performance level on base PlayStation 4 hardware. It seems that there are no new guidelines for ensuring rendering or performance standards on the existing PlayStation 4. One worry is that emphasis may shift to Neo, resulting in poorer experiences for the older hardware. We hope that the sheer weight of the user base ensures that the 'base' PS4 continues to get the care and attention it deserves. Star Wars Battlefront renders at 900p on PlayStation 4 - under the new guidelines issued by Sony, this title would need to operate at native 1080p at the minimum on Neo hardware, if it were submitted as a new title.