RISC OS 6, Preview 1 (Select 4i1), was available in 2007 as a free download to all subscribers to the Select scheme, both present subscribers and those whose subscription was renewed after 30 May 2004 but has since lapsed. RISC OS Six brought portability, stability and internal structure improvements, including full 26/32-bit neutrality. It is now highly modularised, with legacy and hardware specific features abstracted, and other code separated for easier future maintenance and development. Teletext support, device interrupt handler, software-based graphics operations, the real-time clock, the mouse pointer, CMOS RAM support, and hardware timer support have been abstracted out of the kernel and into their own separate modules. Legacy components, like the VIDC driver, and obsolete functionality for the BBC Micro have been abstracted too. AIF and transient utility executable checking has been introduced also to protect against rogue software, while graphics acceleration modules may be provided for the SM501 graphics chip in the A9home and for ViewFinder AGP podule cards. In April 2008 the final release of Select 4 was shipped that included: 8 MB VRAM support in VirtualRPC Filer updates, Keyboard shortcuts, alternative layouts, configurability SVG export in !Draw Select 4 releases are initially compatible with only Acorn Risc PC and A7000 machines. RiscStation R7500, MicroDigital Omega and Mico computers will not officially be supported, as the company does not have test machines available and requires proprietary software code to which they do not have the rights. Lack of detailed technical information about the MicroDigital Omega has also been cited as being another reason why support of that hardware is difficult. In April 2009 the final release of Select 5 was shipped that included: 64K colour screen modes More responsive desktop Improvements to !Paint and !Draw The final release of RISC OS from RISCOS Ltd was Select 6i1, shipped in December 2009, it includes; Configurable Filer toolbars Improved Task Manager Improved Draw with new editing features Configurable File Types menu New Firewall configuration interface Improvements to Pinboard configuration Improvements to Configure itself Post-Acorn development RISC OS 5 RISC OS 5 is a separate evolution by Castle Technology Ltd based upon work done by Pace for their NCOS based set top boxes. RISC OS 5 was written to support Castle's Iyonix PC Acorn-compatible, which runs on the Intel XScale ARM processor. Although a wealth of software has now been updated, a few older applications can only be run