I was playing with my old iBook from around 2000, and I needed to dig into the open firmware commands to set up network booting. Back in 2000 I didn’t know or care about Forth but since the pandemic I’ve gone down a few Forth rabbit holes (thanks CollapseOS!) so it was fun to know what was behind the scenes of the boot interface :)

Open Firmware is still used by IBM Power servers, although not as the "actual" bare metal firmware[1]. It's instead the default firmware interface for the standardized "VM", PAPR. A cut-down variant called SLOF is shipped with QEMU for this purpose, either for full emulation, or combined with KVM on Power hardware for accelerated virtualization.

[1] Technically there's nothing preventing bare metal hardware from implementing PAPR, but to my knowledge, no currently produced hardware does. Same direction that Sun went with their servers late into the game, not long before their acquisition; sun4v ran everything inside LDOMs, with the default configuration giving all resources to a single LDOM, IIRC.

Another famous computer that had it was the OLPC laptop. Lovely machine that deserved more success than it had.

The FreeBSD bootloader was written in Forth for a while. It looks like they may have transitioned off it to Lua by now.

https://marc.info/?l=freebsd-current&m=153469833911665&w=2

open firmware was still default in mac up until ~2008 (I bought a mac mini to play). I'm not sure it's still there though.

All Intel Macs use EFI.