RISC OS 4.39

Released 2002 - RiscPC, Kinetic, A7000 & Microdigital Omega



RISC OS 4.39 was released three years after RISC OS 4.02 and benefited from thousands of improvements and bug fixes. Unlike other versions of RISC OS it was made available in two different ways. The first version was as a 'soft-load' (called 'Select') which booted on top of RISC OS 4.02. The second version was a set of replacement plug in ROM chips (called 'Adjust'). The feature set of these two releases was identical but the 'Adjust' release had to be compressed to fit on the 4MB ROM chips as the uncompressed 'Select' release was almost 6MB in size. RISC OS 4.39 also included updated versions of the RISC OS application suite with the biggest improvements being to Paint and Draw.



RISC OS 4.39 is included with the following products.

RISC OS 4.39 Easy upgrade - from RISC OS 4.02

The RISC OS 4.39 Easy Upgrade provides an easy to install upgrade from RISC OS 4.02. You will benefit from the hundreds of improvements in RISC OS 4.39 but if you need RISC OS 4.02 you can switch back and forth whenever you like. The RISC OS 4.39 Easy upgrade is suitable for RiscPC, A7000, A7000+, VirtualRPC-SE and VirtualRPC-SA. You don't even need to disasemble your computer...

Available for immediate download - 15.00




RISC OS 4.39 - Physical ROMs

  • Series 1/2/3 RiscPC with ARM610 processor, hard disc drive and CD drive.
  • Series 1/2/3 RiscPC with ARM710 processor, hard disc drive and CD drive.
  • Series 2/3 RiscPC with StrongARM processor, hard disc drive and CD drive.
  • A7000 with ARM7500 processor and (optionally) hard disc drive CD drive.
  • A7000+ with ARM7500FE processor and (optionally) hard disc drive CD drive.
  • Castle Technology Kinetic RiscPC with hard disc drive and CD drive.

RISC OS 4.39 - softload ROMs

Compatible with the same machines as physical ROMS and additionally:

  • RiscStation
  • Microdigital Alpha
  • Microdigital Omega
  • Castle Technology RiscPC/A7000+
  • VirtualRPC-SE and VirtualRPC-SA (already supplied with VirtualRPC-Adjust/AdjustSA)

All versions of RISC OS 4.39 are functionally identical.



The following support documents relate to this version of RISC OS:

Further support documents for RISC OS users can be found here.
Further support documents for RISC OS developers can be found here.



RISC OS 4.39 was the culmination of three years of steady development of RISC OS 4.02 by RISCOS Ltd.

In order to fund continued development RISCOS Ltd had introduced the Select scheme. This was a subscription scheme where subscribers were given regular updates to the operating system and other components. Major upgrades were delivered on CD or ISO images, minor upgrades were made available via a special subscriber section of the riscos.com website. All operating system upgrades were delivered in the form of a ROM image which was Soft loaded at start up instead of using the copy of RISC OS stored in ROM chips. All of the 'Select' releases would only function if the computer had RISC OS 4.02 in ROM.

Each release of Select, as well as having an incremented RISC OS version number, was given a release number. These were in the form <year> i <release number>, so, for example, subscription year 2, release 3 would be called Select 2i3. This, like the earlier multiple instances of RISC OS 4.03 caused considerable confusion.

RISC OS 4.39 first appeared as part of the Select scheme as Select 3i4 (release four of year three). The three year development cycle had provided many hundreds of improvements to RISC OS and the addition of a great many new features both in the OS itself and to the RISC OS application suite. RISC OS 4.39 was now fully stable and had been tested on thousands of machines so RISCOS Ltd decided to comply with market demand for an updated physical ROM.

During the development period the additional functionality added to RISC OS had meant that the ROM size had grown bigger than the 4MB that could be accommodated on the RiscPC and A7000 motherboards. This had partly been offset by the removal of !Draw and !Paint from the ROM and their return to the hard disc. This was done so that updated versions of the applications didn't require a new ROM image. In order to squeeze the operating system into the 4MB limit some components were compressed and then expanded into RAM at start up. This is completely transparent to the user.

The new release of RISC OS 4.39 on ROM was called Adjust, a play on the names of the left and right mouse buttons which are called Select (left) and Adjust (right) under RISC OS. Functionally the two versions, soft loaded and ROM are identical. However supplying RISC OS 4.39 in two different ways under two different names caused a great deal of market confusion. 3QD Developments dropped the Select and Adjust names in 2013.

RISC OS 4.39 marked a major change in the development of RISC OS. RISC OS 4.02 was structurally very close to Acorn's RISC OS 3.6 and 3.7. The Acorn OS had a long history dating back to the early RISC OS 2 on the Archimedes models and contained much redundant code needed for older models. Each new version of RISC OS was written using the previous generation as a basis. Often engineers had little time and quick fixes were made in the RISC OS sources which were not fully documented. Each new hardware generation had to be accommodated, often with very short timescales. RISC OS worked well, but there was plenty of room to improve the existing code. During the three years before the release of RISC OS 4.39 the source code was gradually 'tidied up' and re-written and this resulted in a faster, more elegant and much more stable system.

As well as the general work described above there were a number of more 'user facing' improvements. The most obvious of these were the introduction of built in DHCP networking, a built in image viewer for many graphics formats (JPEG, GIF, etc.) which enabled them to be viewed in a desktop window merely by double-clicking on them instead of using a 3rd party application or imported into application which otherwise could not accept them. There was also the option to accommodate multiple users, each with their own individual Setup and Choices.

RISC OS 4.39 is the most functionally advanced version of RISC OS available in ROM. Although RISC OS SIX adds still more improvements and features the inevitable increase in size has meant that it it most unlikely that these later versions of RISC OS will ever be available as a plug-in ROM.



The following articles releate to this version of RISC OS.


© Copyright 3QD Developments - 28/10/2015