Delete me: Upgrading your Raspberry Pi to RISC OS 5.27 (Rev #2)

Introduction

This page details the process for upgrading an already-working RISC OS installation on a Raspberry Pi to RISC OS 5.27.

If you are upgrading from a recent (2017 or later) release, you can skip ahead to here. If you are using an older (2016 or earlier) release, you will have to follow the whole process.

Upgrading from releases earlier than RC15

This will be a two stage process. First you need to upgrade to RISC OS 5.24, then once you have 5.24 working you can upgrade to 5.27. Do not try to upgrade direct to RISC OS 5.27 – it may not work.

• Download the stable ROM image and the stable HardDisc4 image.

• Go to the RISC OS Upgrade page and follow the section titled Procedure for upgrading from RISC OS 5.19 or earlier.¹ Don’t change the OS ROM just yet.

Once you have confirmed that !Boot still works properly, proceed as follows:

• Issue the command:
  *SaveCMOS !Boot.Loader.CMOS
  This saves your current CMOS settings in a place where the Pi bootloader can find them.

• Add the following lines to “CONFIG/TXT” inside !Boot.Loader:
  ramfsfile=CMOS
ramfsaddr=0x508000
  This instructs the Pi bootloader to load the CMOS file ready for use by RISC OS 5.24.

• Replace the RISCOS/IMG file (inside !Boot.Loader) with the RISC OS 5.24 ROM image.

• Reboot.

• If you were upgrading from RC10 or earlier, RISC OS will be using your CMOS settings but none of your old saved CMOS files will work. Save a new backup of your CMOS settings to somewhere safe:
  *SaveCMOS $.Backups.CMOS-RO524 (or a location of your own choosing)

• Once you have RISC OS 5.24 working to your satisfaction (we suggest you try it out for a week or two) you can upgrade to 5.27 as described in the next section.

¹ The InSituBootUpgrade file (supplied with the 5.24 HardDisc4 image) assumes you are upgrading from 5.22, but RC14 was based on RISC OS 5.21 – to successfully use the InSituBootUpgrade process you’d need to run the 5.22 InSituBootUpgrade file first (and finding a copy of the 5.22 HardDisc4 image can be tricky). If you are upgrading from RISC OS 5.19 (Pi releases up to approximately RC10) you cannot use the InSituBootUpgrade process at all.

Upgrading from RC15, 5.24, 5.25 or 5.26

This should be a simple matter of checking your monitor configuration is appropriate for use at RISC OS 5.27, and then performing the upgrade itself. These two items are described in turn below.

Monitor settings

In earlier releases of RISC OS 5, the monitor pixel resolution chosen at boot-up time was controlled by two settings supplied to the Raspberry Pi bootloader (the “hdmi_group” and “hdmi_mode” lines in config.txt). If you want RISC OS to continue using those settings, you should add disable_mode_changes to cmdline.txt². Otherwise, those settings will be ignored from RISC OS 5.24 onwards.

Instead RISC OS can now use EDID to obtain the native pixel resolution directly from the monitor itself. Most monitors manufactured in the last 15 years support EDID, so you should use it if at all possible.

² For example, you may be using a display that only supports a specific pixel resolution, or perhaps you want to use the “AnyMode” utility.

MonitorType and WimpMode

Two CMOS RAM configuration settings – previously all but ignored – are now expected to hold valid information. These are “MonitorType” and “WimpMode”: while RISC OS 5.24 is rather forgiving of unusual values in these two fields, from RISC OS 5.27 they must be correct or the monitor may not display a picture.

So, it is necessary to check that the values are correct before upgrading to 5.27.

• Open a Task window (ctrl-F12) and enter the following two commands:
  *Status MonitorType
*Status WimpMode
  

• If the MonitorType is set a number between 0 and 8, you must change it:
  *Configure MonitorType Auto
  If the monitor type is “Auto” or “EDID” you do not need to change it.

• If the WimpMode is set to a number, you must change it:
  *Configure WimpMode Auto

You should now be ready to perform the upgrade to RISC OS 5.27.

The upgrade process itself

• First, download a Beta ROM image. You won’t be using it just yet, but it’s best to have a few ROM images of different dates, just in case a serious bug was accidentally introduced in a daily build.

• Next, download the Beta HardDisc4 image and upgrade the necessary components in !Boot (e.g. using the “System merge” facility in !Configure). Reboot and fix anything that’s broken.

• Now, replace all the ordinary applications present in the beta HardDisc4 image: simply delete the old ones of the same name and copy the new ones across.

• We recommend you continue using this setup for a week or two, so as to flush out any lurking problems before you upgrade the ROM.

• During this time it’s a good idea to grab a few more beta ROM images of different dates³. You should also check the Bugs and Community Support forums in case there are any problems with recent daily builds.

• You will also need to obtain updated Raspberry Pi firmware before you can install the ROM.

• If you have an old version of the ZeroPain module, delete it (it’s usually installed as !Boot.Choices.Boot.Predesk.!!ZeroPain). Recent versions of RISC OS will run happily without ZeroPain.⁴

• Create a text file called CMDLINE/TXT inside !Boot.Loader (if it doesn’t already exist). The file should contain the text disable_gamma on the first line. See cmdline.txt (Raspberry Pi) for details.

• Finally, install the Beta ROM (RISCOS/IMG) and updated firmware (BOOTCODE/BIN, START/ELF, FIXUP/DAT) into !Boot.Loader and reboot. This completes the upgrade.

³ The build date is mentioned immediately below the download link itself. Although listed as “daily” builds, they do occasionally skip a day or three.

⁴ If you want to continue using ZeroPain, the Beta ROM archive contains the latest version. Installation instructions are included in the archive.

Common problems with the upgrade

• Monitor doesn’t display a picture on boot
  EITHER: You didn’t set MonitorType and WimpMode to “Auto”,
  OR: you didn’t put “disable_gamma” on the first line of cmdline.txt.

• Selecting a 256-colour screen mode produces a black screen (with the mouse pointer still visible)
  You upgraded the ROM but didn’t upgrade the firmware (bootcode.bin, start.elf, fixup.dat).

• Configuration changes don’t survive a reboot
  (1) CONFIG/TXT (inside !Boot.Loader) may be missing the lines that load the CMOS file on boot. Check that the following lines are present:
  ramfsfile=CMOS
ramfsaddr=0x508000
  (2) The CMOS file (inside !Boot.Loader) is missing/corrupted/read-only, or you have another file called CMOS in the root directory of the Filecore partition. Delete any wayward file(s), then issue:
  *SaveCMOS !Boot.Loader.CMOS

• Unexpected behaviour in applications after installing the 5.27 ROM
  This can happen if you installed the ROM without upgrading !Boot as well (or perhaps the attempted upgrade of !Boot didn’t go as well as you had hoped). Alternatively, there may be a serious bug in the specific ROM build you chose (in which case you should replace the ROM with another 5.27 daily build to see if that is any better).