LINUX BOOT.ELF CODE

Fortunately, the EEPROM can be reprogrammed with newer boot code released by the Raspberry Pi Foundation. All current Pi 4B computers were shipped with EEPROM boot code that can only load the necessary files from an SD card. The purpose of the EEPROM boot code is to load and execute the next boot stage contained in start4.elf.

The early boot configuration (bootconf.txt).Note that the Pi 4B does not use bootcode.bin. A proprietary binary blob, similar to bootcode.bin for the older Raspberry Pi models.The EEPROM contains 512 KiB of boot code that is executed after the ROM code is executed.

The system on chip (SoC) of the Pi 4B is the BCM2711B0, which contains an embedded EEPROM. It is after executing the code in ROM that the new boot process differs. Some non-critical boot files are not mentioned, such as fixup4.dat (used for shared memory management between the GPU and CPU).Р”Р„s noted in the older article, a PiРІР‚в„ўs boot process always starts with the graphical processing unit (GPU) running proprietary code from ROM. A few liberties were taken to simplify the drawing. However, some preparation of the Pi 4B might be necessary, depending on its age.Р”Р„ typical Raspberry Pi 4 network boot is shown in the above figure. It is possible to network boot a Raspberry Pi 4 Model B (Pi 4B) without an SD card. This post does contain an up-to-date DHCP server configuration which can also be used to boot older Pi models in addition to the Pi 4B. Some parts were taken from my previous post concerning network booting older Raspberry Pi models. What is written here is based on this page from the Raspberry Pi Foundation and on my own findings. The new boot process will be explained, and a configuration will be offered that will allow network booting of both older and newer Raspberry Pis in a single network. The new boot procedure of the Pi 4B is unlike its predecessors, and this warrants a new post. I did this earlier for older Raspberry Pi models. In this post I explain the ins and outs of network booting a Raspberry Pi 4 Model B (Pi 4B).

Linux-boot.elf