RISC OS IOMD ROM Guide

With RISC OS 5 for IOMD class machines it is at last possible to bridge native ARM based hardware platforms all the way from 1994 to 2020 with a single unified version of RISC OS. Processors made prior to 1994 can only be run in legacy “26 bit” mode, which has been replaced by “32 bit” addressing mode in modern ARM processor designs.

Delivered in virus proof read only memory chips, the upgrade is instantly available at power on with no need to load anything from disc – useful in a discless environment where everything is stored on a network server.

Features and benefits

RISC OS 5 builds on the familiar desktop experience present in earlier versions of the operating system.

One of the key advantages to enabling the extra 6 bits of addressing is that the memory map can be rearranged to make room for bigger applications working on more data.

This means that, for example, large digital photographs can be loaded in one step directly into memory. In principle, applications can use the full amount of memory that can be fitted to the machine (256MB usually).

While there have been over 1500 feature enhancements and bug fixes since the last ROM based version by Acorn, some of the more important differences are summarised here

• Hardware abstracted system so that improvements to other RISC OS 5 hardware targets can benefit all the other computers
• Support for larger files and more files per disc
• Nested window support in the desktop
• Different visual ‘themes’ to choose your preferred desktop look and feel
• A simplified task display
• New BASIC keywords
• A progress/completion bar while copying files around
• Unicode fonts for extended (non Latin 1) character sets
• Built in JPEG rendering including for backdrop photographs
• A wider choice of screensavers
• DHCP support to automatically set up network interface addresses
• Software to connect to Microsoft Windows networks
• Streamlined networking
• Alpha channel sprites
• Built in applications !Draw, !Paint, !Edit, !Alarm, !Help
• Sound mixing for multiple applications
• Commonplace ATAPI CD-ROM driver
• Reads Joliet CD and DVD formats
• Recovery networking utilities
• A built in audio CD jukebox application
• Desktop cut and paste via a global clipboard
• Extra Filer sort/display options
• Numerous speed and stability enhancements

Ensuring you are up to date

It is worth checking that your favourite applications have been adapted to make use of 32 bit mode. Many of then will have been converted to be 32 bit compatible in 2002 to coincide with the release of the Iyonix PC. There may be a charge to upgrade, and to fund future development, but many programs have free updates too.

In the event that an application is no longer supported, it may be the case that an alternative application performs the same job – for example, !Paint is now able to load digital camera photos directly.

More guidance

The ROMs are accompanied by detailed fitting instructions, a simple installer program to automate as much as possible, and videos showing how to fit the ROMs themselves.

Your local user group may also be able to offer one to one assistance on installing the upgrade.

Don’t forget, you can also ask questions on the ROOL forums to learn from other people’s experiences with the more unusual machine setups.

Peripherals: networking

Upgrades are available for the most common network interface cards (NICs) which fit to the motherboard NIC socket, if your network interface resides in a podule expansion card this will need replacing first.

The most common models, residing in the NIC socket, using 10baseT cabling are detailed below

If you use the older 10base2 (coaxial) and 10base5 (thick coaxial) cables, the simplest upgrade route is a replacement network card.

In principle network interfaces residing on the full size podule expansion cards can also work – contact your supplier for details of availability of a firmware upgrade.

Of the supported models in the above table, the flash memory upgrade is included with the install instructions. Those models requiring an EPROM upgrade can be purchased seperately, though the driver can be loaded off disc instead – so the EPROM is not strictly necessary unless dual boot or discless boot is desired.

Peripherals: hard disc

An updated ADFS is included in RISC OS 5 which can read and write to long filename FileCore formatted harddiscs. If you are starting from a version of RISC OS prior to 4.00 it is likely that you will need to reformat the harddisc first – this is usually achieved by backing up your personal data onto a network drive or to a second harddisc, formatting the original, then copying the personal data back again.

The motherboard harddisc interface can accept drives up to 256GB in size, though in practice a smaller size drive will be both cheaper and make more efficient use of the space for small files.

RISC OS 5 requires around 20MB for the default applications and boot sequence, so a solid state parallel ATA drive can also be used.

Being ROM based, the machine will of course still boot without a harddisc, so the exact choice can be made at a later time with the constraint that floppy discs will have to be used in the interim.

Peripherals: CD-ROM

The RISC OS 5 ROM includes support for ATAPI standard compliant CD-ROM drives, which are by far the most common drive type made in the last 15 years. If you have a non standard CD-ROM drive, for example connected via an intermediate expansion card rather than to the motherboard, this may not be compatible.

With the advent of low cost PC peripherals probably the simplest solution is to purchase a replacement drive which states that it is “ATAPI compliant”, this will then be detected automatically by the built in CDFS driver. Such drives retail for around £20 new.

If you are unsure which is fitted, this is not required after the upgrade so can be changed at any convenient time.

Peripherals: expansion cards

Some expansion cards include built in firmware held in read only memory on the expansion card itself. For the expansion card to be recognised by RISC OS 5 the firmware must be marked as 32 bit compatible, in the same way that applications and modules must be.

Contact the supplier of the expansion card for details of a 32 bit upgrade path, many were updated to coincide with the release of the Iyonix PC which also ran the processor in 32 bit mode.

If you are unsure of which podule expansion cards are compatible or not, this is not required for the machine to startup so can be changed later.

Peripherals: optional

The floppy disc drive is supported and can be used to read and write both FileCore format and DOS/Windows format diskettes. If you do not plan to use these please note that the drive is also used to signal self test failure results via the floppy drive LED, so it should be left connected at least during testing.

As the motherboard is over 10 years old now the standby battery, which keeps the clock running and saved configuration settings in CMOS memory, may have reached the end of its working life.

Installing the ROM chips requires taking the lid off the computer, so it may be advisable to inspect or replace the battery backup at the same time. Spare batteries are available from CJE micros, though do require access to a soldering iron to install.