> You can write a simplistic boot sector loader for PC in a few hundred ASM opcodes, that would be a lot more difficult for the average ARM bootloader because t

> You can write a simplistic boot sector loader for PC in a few hundred ASM opcodes, that would be a lot more difficult for the average ARM bootloader because there's a lot more to do before you can just call into Linux. In general you won't even have RAM or caches available when u-boot begins executing. This is exactly the point OP's getting at though, and the exact "discovery" features you handwave away. If I write an OS (or bootloader) on x86 w/ BIOS/uEFI, I can easily query available memory and start using it. Meanwhile u-boot has to be told via an external resource how much RAM is available before it begins initializing. This is fine for embedded/bespoke development (since you'll know the hardware you're developing for and can make assumptions), but a pain for general OS development where you have to inform the bootloader/OS of every devices capabilities.