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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 RISC OS 5.24 onwards
RISC OS 5.24 was the first stable release for the Raspberry Pi. Bugs in earlier (development) releases are not listed here.
| 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. |
| Note: | Does not affect models with only one USB port (e.g. Pi 3A+). |
| Versions affected: | 5.24, 5.26 |
| Fixed in: | 5.25 builds dated 2018-06-03 and later, plus all 5.27 builds. |
| Workaround: | Use an external USB hub for all USB1.1 devices (but see “Keyboard not recognised during boot” below). |
| 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: | 5.27 builds dated 2018-12-02 and later. |
| Pi 3A+ GPIO layout | |
|---|---|
| Symptoms: | The GPIO layout of the Pi 3A+ is not properly enumerated (read off end of table). This can make controlling the Pi 3A+ GPIO pins anywhere from difficult to impossible. |
| Version affected: | 5.26 |
| Fixed in: | 5.27 builds dated 2018-12-02 and later. |
| 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, 5.25, 5.26, 5.27 |
| 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: | On booting-up with an external USB hub connected, the message “No keyboard present – autobooting” appears on the screen. Also, trying to use Shift-Break to reboot to the command line won’t work: RISC OS will always boot to the desktop. |
| Note: | It is the mere presence of the external USB hub that causes the problem. It will still happen if you move the keyboard to a built-in port but leave the hub attached. |
| Versions affected: | 5.24, 5.25, 5.26, 5.27 |
| Fixed in: | (No fix available) |
| Workaround: | If you want to use Shift-Break, temporarily unplug the USB hub and connect the keyboard to a built-in USB port on the Pi. The USB hub can be reconnected once the reboot is complete. N.B. Some keyboards (including the “Raspberry Pi Official Keyboard”) have their own USB hub. The stated workaround will – obviously – not work with this type of keyboard. |
| Selecting a 256-colour mode results in a blank screen | |
|---|---|
| Symptoms: | On selecting a 256-colour screen mode, the screen goes blank but the mouse pointer is still visible. If you press F12, blind-type *wimpmode X800 Y600 C16M and press Enter twice, the screen display reappears. |
| Note: | This can also happen at boot-up (e.g. a monitor type of “Auto” will default to 640×480 pixels, 256 colours). |
| Version affected: | 5.27 |
| Fix: | Upgrade the Pi firmware (bootcode.bin, fixup.dat, start.elf). Firmware versions from January 2019 onwards will fix the problem. |
| 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. |
| Note: | This can be distinguished from the previous case because (a) it can happen at any time, not just at a mode change, and (b) the mouse pointer disappears as well. See this forum thread for more details. |
| Versions affected: | 5.25, 5.27 |
| Fixed in: | (No fix available) |
| Workaround: | Add disable_gamma to the first line of cmdline.txt |
| Pi 4 screen display is too bright | |
|---|---|
| Symptoms: | The screen display on the Raspberry Pi 4 is unnaturally bright. |
| Version affected: | 5.27 |
| Fixed in: | (No fix available) |
| Workaround: | Add disable_gamma to the first line of cmdline.txt |
| Note: | Work on porting RISC OS to the Raspberry Pi 4 is still ongoing. See Raspberry Pi 4 port status for details. |
For bugs applicable to all platforms (including the Raspberry Pi) see the Bug tracker page and the Bugs forum.
A note on RISC OS 5.27
RISC OS 5.27 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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