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Because these kinds of boards don't typically have BIOS/firmware chips, the booting options are limited to what is provided by the SoC's boot ROM. An USB host s

by dezgeg 11y ago

Because these kinds of boards don't typically have BIOS/firmware chips, the booting options are limited to what is provided by the SoC's boot ROM. An USB host stack is immensely complicated and as such something that manufacturers wouldn't want to put in their ROMs (although I recall some Cortex-M0 chips actually implement this). Many (maybe even most?) SoCs, including at least all previous Allwinner chips do support booting directly from SD cards, though.

gcb0 11y ago
... flash a "boot from SD card filesystem" firmware in the factory?
- dezgeg 11y ago
  No, the boot ROM supports from booting an SD card. Though not in the sense of booting any OS like Linux, but booting a board-specific second stage bootloader like U-Boot.