Software information: Raspberry Pi: Firmware (Rev #1)

Pi bootloader files

The boot loader partition contains, at minimum, these five files:

bootloader.bin
The boot loader for the CPU.

start.elf
The GPU firmware. Forms a matched pair with fixup.dat

fixup.dat
Additional code for the GPU. Forms a matched pair with start.elf

riscos.img
The RISC OS ROM

config.txt
Configuration parameters for the boot loader. See below for suggested contents.

The following file is optional:

cmdline.txt
Additional parameters to be passed to the kernel (i.e. RISC OS). Discussed in more detail below.

Obtaining Pi firmware

RISC OS 5.24 and RISC OS 5.26 should use the firmware supplied with the distribution: there is no point in using later firmware.

A code change in late January 2019 means that RISC OS 5.27 cannot use the firmware supplied with earlier distributions, but there is a risk in using the absolute latest firmware as recent changes in the firmware could have had a detrimental effect on RISC OS operation.

The current recommendation is to use January 2019 firmware obtained from the download site

The files you need are: bootcode.bin, fixup.dat, start.elf.

• To obtain firmware for a given date, choose each component in turn and click on the History button.
• start.elf and fixup.dat are a matched pair, so you must use files released on the SAME date.
• bootcode.bin is not as heavily constrained, but for maximum peace of mind you should use the release closest in date to the chosen version of start.elf/fixup.dat.

config.txt parameters

These tend not to change much between RISC OS releases. The following parameters should be suitable for RISC OS 5.24, 5.26 and 5.27:

fake_vsync_isr=1
framebuffer_swap=0
gpu_mem=64
init_emmc_clock=100000000
ramfsfile=CMOS
ramfsaddr=0x508000
kernel=RISCOS.IMG

Welcome to RISC OS Pi contains details of several other parameters (disable_overscan, hdmi_pixel_freq_limit etc.) that may be of interest to RISC OS users.

For a full list of boot options, see the documentation pages on the Raspberry Pi website
and/or elinux.org

cmdline.txt parameters

The following parameters can be supplied in cmdline.txt. Parameters must be space separated on the first line, so if you wanted to specify two parameters you would do it like this:

disable_mode_changes disable_gamma

Parameters available are:

disable_gamma
Introduced in July 2018, this prevents use of the hardware gamma tables in BCMVideo. Use this parameter if you experience screen blanking problems while running RISC OS 5.25 or RISC OS 5.27.
This parameter is not needed at 5.24/5.26, as the hardware gamma tables are disabled by default.

disable_mode_changes
Locks the screen pixel resolution to the one chosen at startup. Can be useful with third-party utilities such as “AnyMode” to force upscaling of lower-resolution screen modes.
PLEASE NOTE: You may experience problems when using this parameter if your monitor cannot display a 1920×1080 picture. Specifying the appropriate hdmi_group and hdmi_mode settings in config.txt should get you going. See the documentation page on the Raspberry Pi website for details.