RISC OS bugs specific to the Raspberry Pi
category: RaspberryPi
This page lists the bugs in RISC OS that affect the Raspberry Pi only.
This is NOT a list of all bugs in RISC OS. For bugs applicable to all platforms, see the Bug tracker page and the Bugs forum.
Bugs in the current stable release (RISC OS 5.30)
Some of these bugs are long-standing and will affect earlier releases of RISC OS as well as 5.30 itself.
| Config changes lost when two CMOS files exist on SD card | |
|---|---|
| Symptoms: | If you take a backup copy of the CMOS file and save it on the SD card as “$.CMOS”, RISC OS will write to that file (instead of $.!Boot.Loader.CMOS) whenever a configuration change is made. This means that subsequent configuration changes will not be carried over to the next session. |
| Versions affected: | 5.24 onwards |
| Fixed in: | (No fix available) |
| Workaround: | When taking a copy of the CMOS file, give it a different name (e.g. “CMOS-copy” or “CMOS-backup”). |
| Keyboard not recognised during boot | |
|---|---|
| Symptoms: | The message “No keyboard present – autobooting” appears on the screen during boot. Trying to reboot to the command line (e.g. via “*Configure NoBoot”, or by holding down Shift during power-on) won’t work: RISC OS will always boot to the desktop. |
| Cause: | This can happen if you boot-up the Pi with additional USB devices connected, particularly if you are using an external USB hub. RISC OS allows only 5 seconds during boot for USB discovery, so if the keyboard is the last to start up it can be missed. |
| Note: | A re-scan for USB devices happens when the Wimp starts up, so devices missed during boot will be discovered when the desktop appears. |
| Versions affected: | All 1 |
| Fixed in: | (No fix available) |
| Partial workaround: | If you want to boot to the command line (e.g. by using Shift power-on), disconnect all other USB devices – including hubs – and power-on with only the keyboard attached. This is not guaranteed to work, as some keyboards can be slow to start up. |
1 The message is less likely to appear on development versions of RISC OS (5.27, 5.29, 5.31) as extra diagnostic messages appear during boot, allowing USB devices slightly longer to start up.
| Boot-up stalls at “Contacting DHCP server” | |
|---|---|
| Symptoms: | The message “Contacting DHCP server for Ethernet over USB interface” appears during boot. Instead of timing-out after 40 seconds, boot-up never proceeds any further. |
| Cause: | The expected Ethernet interface does not exist. This usually means this is the first time ever you have booted a Pi model without a built-in Ethernet port (Pi Zero, Pi A+ and Pi 3A+). |
| Versions affected: | All |
| Fixed in: | (No fix available) |
| Workaround: | Models with no Ethernet interface, press ESC to reach the desktop (click “Cancel” on the dialogue box that appears) then disable networking by going to “Configure > Network > Internet” and unticking “Enable TCP/IP Protocol Suite”. |
| Out-of-spec USB devices can cause a system crash (Pi 4 only) | |
|---|---|
| Symptoms: | On the Pi 4, trying to use an out-of-spec USB device (e.g. certain models of memory stick) can cause the error “Abort on data transfer” and/or a system crash. |
| Versions affected: | 5.27 onwards |
| Fixed in: | (No fix available) |
| Partial workaround: | Try interposing a USB2 hub between the Pi 4 and the device. This may allow some (but not all) of the problem devices to be used. |
| Cannot change certain HDMI parameters | |
|---|---|
| Symptoms: | A few of the HDMI settings in config.txt (e.g. “hdmi_pixel_freq_limit”) have no effect. This can prevent selection of some monitor pixel resolutions. |
| Cause: | This is a side-effect of a Raspberry Pi firmware change made in May 2020. |
| Versions affected: | 5.28 onwards |
| Fixed in: | (No fix available) |
| Workaround: | See the “Increasing the screen size” section of config.txt (Raspberry Pi). |
| Screen display has red and blue swapped | |
|---|---|
| Symptoms: | After upgrading to recent firmware, 16-million colour screen modes are displayed with red and blue swapped (e.g. the Raspberry Pi logo is purple instead of dark red). See this forum thread for more details. |
| Versions affected: | 5.28, 5.30 |
| Fixed in: | 5.31 builds dated 2024-06-06 and later |
| Workaround: | Look for the framebuffer_swap=0 line in config.txt. If it is missing, add it. If it is present, try changing it to to read framebuffer_swap=1 |
Bugs affecting previous stable releases (RISC OS 5.24 to 5.28) only
RISC OS 5.24 was the first stable release for the Raspberry Pi. Bugs in earlier releases are not listed here.
| Pi 1A/1B SD card detect switch | |
|---|---|
| Symptoms: | At RISC OS 5.28, the SD card detect switch on a Pi 1 no longer works properly. RISC OS can fail to notice that the SD card has been removed or replaced on a Pi 1. |
| Version affected: | 5.28 |
| Note: | Other Pi models (Pi Zero, Pi 2, Pi 3, Pi 4) are not affected. |
| Fixed in: | 5.30 |
| Workaround: | None. |
| Built-in USB ports | |
|---|---|
| Symptoms: | USB1.1 devices (e.g. keyboards, mice) can misbehave if you mix USB1.1 and USB2 devices on the built-in USB ports. |
| Versions affected: | 5.24, 5.26 |
| Fixed in: | 5.28 |
| Workaround: | Use an external USB hub for all USB1.1 devices |
| Lightning symbol | |
|---|---|
| Symptoms: | The Pi 3B+ may flash the “lightning” (low voltage warning) symbol during heavy SD card access. |
| Version affected: | 5.26 |
| Fixed in: | 5.28 |
| Pi 3A+ cannot control GPIO pins | |
|---|---|
| Symptoms: | The GPIO layout of the Pi 3A+ is not properly enumerated (read off end of table). As a result it may not be possible to control some of the GPIO pins on the Pi 3A+. |
| Version affected: | 5.26 |
| Fixed in: | 5.28 |
Bugs affecting development builds only
| Screen goes blank at a random time | |
|---|---|
| Symptoms: | After a period of normal operation (ranging from a few seconds to several hours) the screen will abruptly go blank. The only way of restoring a display is to power off and power on again. See this forum thread for more details. |
| Note: | Stable builds are not affected, as gamma is disabled by default. |
| Versions affected: | 5.25, 5.27, 5.29, 5.31 |
| Fixed in: | (No fix available) |
| Workaround: | Add disable_gamma to the first line of cmdline.txt |
For bugs applicable to all platforms (including the Raspberry Pi) see the Bug tracker page and the Bugs forum.
A note on RISC OS 5.31
RISC OS 5.31 is the current development release. It is the nature of software development that individual builds may introduce bugs that are swiftly fixed (or sometimes not-so-swiftly fixed). Developers who wish to know what changes were made on what dates are advised to consult the GitLab repository rather than relying on this wiki.
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