Raspberry Pi Bare Bones: Difference between revisions
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* start.elf: this is the RPi firmware (same as BIOS on IBM PC). This also runs on the GPU. |
* start.elf: this is the RPi firmware (same as BIOS on IBM PC). This also runs on the GPU. |
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Simplified when the RPi powers up the ARM CPU is halted and the GPU runs. The GPU loads the bootloader from ROM and executes it. That then finds the SD card and loads the bootcode.bin. The bootcode loads the firmware, start.elf which handles the config.txt and cmdline.txt. The start.elf loads the kernel*.img and at last the ARM CPU is started running that kernel image. |
Simplified when the RPi powers up the ARM CPU is halted and the GPU runs. The GPU loads the bootloader from ROM and executes it. That then finds the SD card and loads the bootcode.bin (except RPi4 which has a big enough ROM to include bootcode.bin as well). The bootcode loads the firmware, start.elf which handles the config.txt and cmdline.txt. The start.elf loads the kernel*.img and at last the ARM CPU is started running that kernel image. |
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To switch among ARM modes, you have to rename your kernel.img file. If you rename it to '''kernel7.img''', that will be executed in AArch32 mode (ARMv7). For AArch64 mode (ARMv8) you'll have to rename it to '''kernel8.img'''. |
To switch among ARM modes, you have to rename your kernel.img file. If you rename it to '''kernel7.img''', that will be executed in AArch32 mode (ARMv7). For AArch64 mode (ARMv8) you'll have to rename it to '''kernel8.img'''. |
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