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  • The PowerPC architecture is also interesting because some motherboards had a Turing-complete BIOS - Openfirmware (basically the Forth programming language with some preinstalled functions). This allowed booting directly from BIOS without bootloader if you know how to configure your BIOS Commented Jan 8, 2019 at 1:21
  • Hey, just curious, NTLDR can load linux kernel directly? I heard that NTLDR can chainloader grub4dos and then load the linux kernel. Commented Jan 8, 2019 at 4:09
  • @slebetman: More precisely, OpenFirmware was developed by Sun for SPARC and then adopted by the PowerPC alliance (IBM, Apple, Motorola) for the PowerPC Reference Architecture, and specifically by Apple for PowerPC-based Macintoshs. One of the powerful aspects was that simple drivers could be stored inside ROM chips on the expansion cards, or in some designated boot area of a HDD, and since they were written in bytecode against a known specified ABI, they would work regardless of which CPU architecture and OS you were trying to boot. Commented Jan 8, 2019 at 14:07
  • E.g. you could have RAID adapter which has its OpenFirmware driver inside a ROM chip, then the OpenFirmware environment could use that driver to access the RAID, inside the RAID, there could be another driver for the partition table format, which would allow the OFW environment to find the partitions, at the beginning of each partition would be an OFW driver for the filesystem, which would allow the OFW system to find the kernel, and the kernel would have a small bootloader written in OFW bytecode at the beginning. Commented Jan 8, 2019 at 14:10
  • GRUB can operate in a similar way, but the difference is that all those drivers have to be written specifically for GRUB, whereas the beauty of OFW was that the device would bring its drivers with it, which means that even devices that didn't yet exist when the OFW environment was written would just "magically" work. UEFI can also operate in a similar way, but its "portable bytecode format" is essentially a subset of DOS, which is the main reason why Itaniums still need an x86 emulator. Commented Jan 8, 2019 at 14:13