ARC was a specification, more like Open Firmware than specific implementation. NT before 6.0 can in fact boot only using ARC - the NTLDR code is responsible fo

ARC was a specification, more like Open Firmware than specific implementation. NT before 6.0 can in fact boot only using ARC - the NTLDR code is responsible for emulating ARC on PC BIOS systems. It originated on MIPS, iirc, and SGI MIPS machines used a related firmware. On Alpha, there was AlphaBIOS firmware (first as an option that you needed to reflash, then as single mostly integrated package with SRM) which fulfilled the ARC standard combined with BIOS-like setup program.