Further details of the PlayStation 3 have emerged from Sony's business briefing in Tokyo today, with the firm revealing that the device's hard drive will not be optional, and that a free online service will roll out for the launch of the console.

It had previously been thought that the PS3 hard drive would be an optional device, as the hard drive on the Xbox 360 is, but Kutaragi was adamant today that the component, which will ship at 60Gb but can be upgraded, is required by the console.

As expected, the drive will allow the PlayStation 3 to act as a home media server, which can store and manipulate various different types of media that can then be accessed from other devices. However, it will also be capable of running a version of the Linux operating system, and will be key to the online service the company is planning.

That service, which is clearly designed as a direct competitor to Microsoft's Xbox Live, will be entirely free and will be available from the launch of the console, offering standard features such as game lobbies, player matching, voice chat and a variety of commercial features including software which will be distributed over the network and can be stored on the hard drive.

This latter feature is particularly interesting in light of the information received from development sources by GamesIndustry.biz earlier this week, indicating that Sony may be planning digital distribution of some of its PS2 and PSone back catalogue on PS3.

The company also this morning confirmed once again that PlayStation 3 will be entirely backwards-compatible with PS2 and PSone titles, and revealed that the new console will be able to upscale those games into high definition video formats.