Over the years of the RISC OS Ltd. Select scheme, I've generally been impressed by the various improvements and speedups along the way and although I don't use every single feature, long gone are the days when I could just sit down and use older versions of RISC OS.

Quite soon, you reach the point where familiarity with the little subtle improvements (as well as the big ones) makes it difficult to use a machine without those features. Having been a Select subscriber for a long time, it is difficult to remember exactly which features appeared in which versions, but the latest RISC OS 6.14 is quite dramatically different from the humble 4.02 and even 4.39 released by RISCOS Ltd.

When it was initially announced, many people said that they were not keen on a subscription based system. In a market the size of the RISC OS one, though this has been required to ensure funding for the developments that have taken place. People easily forget this and expect quality software for free - this just doesn't happen in small markets, people need to accept this.

As I meet lots of people at RISC OS shows and clubs I'm sometimes surprised that some people don't Some people I've spoken to seem to be confused by the various names and version numbers given to RISC OS releases, so this is intended to be a round up of what's available under Select and Adjust and which machines can run which versions. Any mistakes are my own. When RISCOS Ltd. obtained their license to develop and distribute RISC OS, the available hardware was Risc PC and A7000s. RISC OS 4 was targeted at those machines. Anything earlier is not relevant to this article.

Sometime after RISCOS Ltd. was set up, 3rd parties were able to produce machines and license RISC OS from RISCOS Ltd. for them. This led to the release of the Microdigital Mico and Omega computers as well as the Riscstation R7500 computers in a choice of Desktop and Tower configurations. Somewhere along the way, Castle produced their Kinetic processor card for the Risc PC. Each of these computers (sometimes referred to as 26-bit machines - although that would also include older RISC OS 2 and 3 computers also), including the Kinetic processor card ran a slightly different version of RISC OS 4 - 4.03. I believe RISC OS 4.04 was also produced for the Kinetic processor, although I don't know what functional difference this contained.

The Select scheme was announced in May 2001 and was created for two main reasons, one to fund development of the operating system going forward, and secondly to allow upgrades without having to take ROMs out of your computer and swap them for a new set - thus reducing time to market for updates and giving a back-out option if there were problems.

RISC OS versions

RISC OS 4.00 and 4.01 were originally released but fairly quickly replaced by 4.02. RISC OS 4.02 was the only ROM based version that could be fitted to machines for quite some time. This enabled upgrading from earlier, Acorn Produced 3.5, 3.6 and 3.7X versions. RISC OS 4.02 was also the pre-requisite for softloading later versions.

RISC OS Select

This is the name given to the Subscription scheme and also to Softloaded versions of RISC OS. Select numbering was based on a Scheme and issue number, so RISC OS Select 3 issue 4 was the 3rd wave of the scheme and issue 4 of that wave. Each successive release of Select had a new issue number, and where the core version of RISC OS changed within that release, RISC OS itself had a new version number as normal. RISC OS Select 3, issue 4 contained RISC OS 4.39, for example.

RISC OS Adjust

This was the name given to the ROM based versions of RISC OS. The first time it was used was at version 4.39 - functionally identical to the softloading 4.39 (aka Select 3i4), this version was repackaged into physical ROM chips so that users could directly boot from 4.39 rather than 4.0X. By the time 4.39 had been produced, the ROM images were up to 6Mb in size, yet the physical ROMs that the computers used were only 4Mb. RISCOS Ltds developers put lots of effort into squeezing 4.39 into 4Mb. I suppose that you could put RISC OS 4.0X versions under the Adjust banner, but these all happened before the concept of softloaded releases were available, so the term had not been used at that time. At its simplest, RISC OS Select means softloaded and RISC OS Adjust means in ROM. To date, there has only been one named release of RISC OS Adjust for 26-bit machines (RISC OS 4.39). There has been another Adjust release though - actually the of them!. These were for the A9Home computers and were flashed into that machine's ROM. Early A9Home's shipped with Adjust32 in the form of RISC OS 4.40, some users also saw RISC OS 4.41, but most will have only had RISC OS 4.42. Being in Flash ROM, each of these versions qualify as RISC OS Adjust, the 32 refers to the fact that it is a full 32-bit build of RISC OS so as to be compatible with the ARM 9 processor in the A9Home. RISC OS 4.4X was developed on from 4.39 but also included some features that were to be released in RISC OS 6 for 26-bit machines.

Who can use what

As far as I am aware, anyone with a Risc PC, A7000/A7000+, Riscstation R7500, Microdigital Mico and Microdigital Omega should be able to run RISC OS Select 3i4 (aka RISC OS 4.39) quite happily. So far, there are no versions of Select (softloads) available for the A9Home computer. After the release of the A9Home, RISCOS Ltd. released RISC OS Select 4 (as RISC OS 6.02 initially). Given that it is much more recent, the RISC OS Select 4 (and Select 5) releases of RISC OS 6 are briefly listed below:

• Select 4i1 - RISC OS 6.02
• Select 4i2 - RISC OS 6.06
• Select 4i3 - Disc components update to 6.06
• Select 4i4 - RISC OS 6.10
• Select 5i1 - RISC OS 6.14 - current at time of writing.

As far as RISC OS versions after 4.0X are concerned the Castle Kinetic processor card is irrelevant and is just treated and supported as a StrongArm Risc PC (which it is), so this variant of Risc PC can use any version that standard Risc PCs can.

Officially, RISC OS 6 is available for Risc PCs and A7000/A7000+ machines. For the avoidance of doubt, this *includes* Virtual Acorn's Virtual Risc PC products. Therefore regardless of which version of Risc PC (600, 700, StrongArm, Kinetic) or Virtual Risc PC (VRPC SE, VRPC SA / Adjust) or A7000 variant, RISC OS 6 should just run. Additionally, RISC OS 6 supports the Viewfinder Graphics card that was available for the Risc PC (check with RISCOS Ltd. for specific details).

RISC OS 6 is not officially supported on Microdigital or Riscstation machines and may or may not work. So in summary, if you've got a Risc PC, A7000/A7000+ or Virtual Risc PC of any kind (provided you have enough memory), you could be using the very latest version of RISC OS (6.14). This brings many benefits including new user features, stability and speed improvements. I certainly wouldn't want to go back on my Risc PCs and Virtual Risc PC laptop.

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