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Guide to RISC OS Hardware

RISC OS 2 was first released in 1989, and since then there have been many different machines capable of running the OS. The range of systems capable of running modern versions of RISC OS are more limited, however – this page aims to provide a guide to what is available.

More information about the different versions of RISC OS mentioned below can be found in our guide to RISC OS versions and our brief history of RISC OS.

Modern systems

A modern RISC OS system, which will be practical for day-to-day use, ideally needs to be running RISC OS 4, RISC OS 5 or RISC OS 6. It should also have a relatively fast processor (in ARM terms, that is – compared to mainstream desktop systems, ARMs need significantly slower clock speeds to achieve the same “usability”). In practice, this limits the available systems to a small selection of native-ARM and emulated machines.

Modern systems fall into two groups: for convenience, these are usually referred to as “26-bit” and “32-bit” despite both being 32-bit in the conventional sense. 26-bit systems are compatible with more old software, while modern ARM processors are 32-bit only. In practice this isn’t a problem: any software that is still being developed will be compatible with both 26- and 32-bit systems, and 32-bit systems can run most incompatible 26-bit software using an emulator called Aemulor.

Virtual Acorn

If you already have a Mac or Windows system, then running RISC OS emulated on this makes a lot of sense: not only does it save the expense and space requirement of new hardware, it also allows the two systems to co-exist in a way which can only otherwise be achieved using a network.

Virtual systems emulate a very fast RiscPC, meaning that they can easily retain compatibility with old software by pretending to have a fast 26-bit processor. Different versions are available, emulating the ARM710, ARM7500 and StrongARM processors. The are supplied with RISC OS 4.02 and RISC OS 4.39 as standard, although they can all be upgraded to run RISC OS 6.

Copies of Virtual Acorn can be bought direct from the developer (Virtual Acorn) for installation on any Windows or Mac OS X machine. Alternatively, preconfigured Windows-based systems can be bought from a number of suppliers including R-Comp and Stuart Tyrrell Developments – these come pre-configured to run both RISC OS and Windows as a “hybrid” system.

Virtual Acorn
R-Comp (RISCube, SpaceCube and RISCBook systems)
Stuart Tyrrell Developments (The A6)

The Iyonix PC

If you would prefer to own a native ARM-based system, then there are two choices for new hardware. The first is the Iyonix PC, based around the XScale 80321 processor and developed by Iyonix Ltd. Built on a standard ATX-format motherboard, it comes in a number of desktop, tower and cube cases.

Using a 600MHz processor, the Iyonix is currently the fastest native system capable of running RISC OS – as noted above, due to the relative efficiency of RISC OS, comparing this to the speed of modern processors on other systems isn’t that useful.

When new, the Iyonix comes with RISC OS 5.13 as standard; second-hand models may have older versions of RISC OS 5 fitted. If you plan to make use of USB, it’s worth checking if the machine comes with USB2 support: prior to the arrival of RISC OS 5.13, this was a chargeable upgrade from the USB1 support which came as standard.

The Iyonix comes with USB, RS232 serial, audio in/out and gigabit networking ports. It takes standard PCI expansion cards (used as standard for graphics and USB), which can take cards aimed at the Windows market when suitable RISC OS drivers have been written. The Iyonix Classic is currently the only RISC OS system in production to take the old Acorn expansion podules (again, if suitable drivers have been written).

Iyonix Ltd

The A9home

The other ARM-based system currently in production is the A9home, developed by Advantage 6 and marketed by CJE Micro’s. Unlike more conventional desktop systems, it comes in a small blue box which is (literally) pocket-sized.

The small size hides a well-featured machine, comprising of a 400MHz ARM9 processor, 128Mbytes of SDRAM, 8Mbytes Video RAM and a 40Gbyte hard disc. Due to its compact size, and unlike the Iyonix, neither the RAM nor the hard disc can be upgraded. Communication with the outside world is via USB, RS232 serial, PS/2, audio in/out and 10/100Mbit network ports. The USB support is USB1 only.

Currently the A9home runs RISC OS 4.39 in 32-bit mode. It is hoped that eventually RISC OS 6 will become available for the machine. Expansion is limited, and even CDROM and floppy disc drives must be added via the USB1 interface.

The RiscPC

While no longer in production, the RiscPC is the last of Acorn’s machines to remain really useful. Designed in 1994, the expandibility – in particular the ability to change the processor with the swap of a daughtercard – has meant that many are still in use today. The fact that the RiscPC is the last native system to run in 26-bit mode may have helped this longevity, along with the fact that they continued to be manufactured by Castle Technology long after the demise of Acorn.

Although not available new, there are many RiscPCs available for sale on the second-hand market. Prices will often start at upwards of £50, but watch out – the cheaper ones will often have a low specification and may be best avoided.

The RiscPC can contain a number of different processors. The best ones to go for today are those with a StrongARM (usually clocked at 200-300MHz) or a Kinetic (a StrongARM with additional fast RAM fitted on the processor card, developed by Castle Technology in 2000). Machines fitted with ARM710 and ARM610 processors are still around, but are probably too slow to be productive with much modern software.

RiscPCs can come with a wide range of operating systems. Originally shipped with RISC OS 3.5, machines with a StrongARM must be running RISC OS 3.7 or later and those with a Kinetic must have at least RISC OS 4.03. For a usable system, RISC OS 4 or RISC OS 6 should be considered the only practical options these days – upgrading is a relatively straightforward process.

In terms of expansion, RiscPCs take up to 256Mbytes of memory in the form of SIMMs, plus up to 2Mbytes of Video RAM (upgrades for the latter are very hard to come by). An on-board IDE interface can take two devices, but for compatibility with modern hard discs look for a machine with a third-party IDE podule fitted. All machines came with a HD floppy disc drive, and most these days should have a CD or CDR/W drive as well.

On the back, RiscPCs came with VGA video, RS232, parallel and headphone ports. Keyboards were PS/2, while the machine was the last to use the Acorn quadrature mouse – adaptors to accept PS/2 mice are easy to find. Many machines will have podules fitted to offer additional ports: USB1, SCSI and 10/100Mbit networking are common, and many will have a Viewfinder card to offer higher quality video output via a standard AGP graphics card.

If looking for a second-hand RiscPC, the best advice is to shop around and see what is available before parting with any money.

Older systems

RISC OS has been around since 1989, and the original machines that it ran on were launched in 1987, so there are plenty of older systems around. While much older hardware is probably of historical interest only, some of the more recent systems can still be useful. That said, for serious desktop use today, a machine listed under Modern systems (above) should be considered a more practical choice.

Some of the recent machines listed here were developed by third-parties after Acorn’s demise, but the majority were designed and developed by Acorn themselves before their breakup in 1998.

The Omega

The Microdigital Omega was launched in 2002, and was seen as a competitor to the Iyonix PC. Although there are a number of satisfied users still around, few were made and development of all the specified add-ons was never completed.

The system was based around a StrongARM processor, with custom hardware comprising a number of FPGAs to emulate the IO systems of a RiscPC; Acorn expansion podules were not supported. It could support up to 1Gbyte of RAM. The Omega initially shipped with RISC OS 4.03, and can be upgraded to later versions of RISC OS 4.

Although the Omega still provides a usable desktop system, support is limited and some users report problems using newer versions of RISC OS. As a result, these days it is probably a system best suited to an enthusiast.

The Mico and R7500, Networkx and Scorcher

The Mico, from Microdigital, and the R7500, Networkx and Scorcher series, from RiscStation, were two ranges of ARM7500-based computers released in the late 1990s. Both systems shipped with RISC OS 4.03.

All the systems are capable of running modern software, but can not physically accept Acorn expansion podules. Performance may seem limited to those familiar with modern systems, and support may be hard to come by.

A7000 and A7000+

Aside from the RiscPC, these were the only Acorn-developed machines other than the RiscPC which could run RISC OS 3.5 or better. Based around the ARM7500 and ARM7500+ respectively, they were similar in spec to the Mico and R7500 series machines and were produced in the second half of the 1990s.

Although capable of running modern software, their expansion capabilities were limited and their support for modern screen resolutions is lacking. As a result, they are probably best avoided for modern desktop use.

A3010, A3020 and A4000

The one-box A3010 and A3020 (with the keyboard in the same box as the computer itself) and the A4000 with a conventional separate keyboard were based around the ARM250 series of processors and finished production in around 1995.

Compared to modern systems they were slow, and they could only be used with RISC OS 3.1 – this rules them out for a lot of modern software. Expansion capabilities were limited.

A300, A400, A500 series, A3000, A5000 and A4

This final group of machines are the oldest in this list. Based around the ARM2 and ARM3 processors (with all being capable of an upgrade to ARM3 if not already fitted), they shipped with RISC OS 3.1, RISC OS 2 or (in the case of those made before 1989) the Arthur OS. Most would have been upgraded to RISC OS 3.1 during their life.

Expansion capability varied: most could accept up to four podules, but the one-box A3000 could only manage a single one mounted in an external box. As would be expected for machines designed before 1990, they are very slow by modern standards and RISC OS 3.1 limits the software that they can run.

The A4 was Acorn’s only laptop machine, and was effectively an A5000 in a laptop case. Running RISC OS 3.1, it came with additional support for the battery and 15-level greyscale display.