Yes. BIOS. Real mode. Not that I've been missing them these 30 years, and they are still in place. It gives a weird feeling.
I mean, if you target ancient baroque hardware like e.g. ZX Spectrum, you specifically target an ancient machine. But this is expected to work on any modern x86 hardware, while it feels like code for a 80286, and likely would run there. And this ancient stuff is still supported and actively used.
How much emulation is required to get System/360 code running on a modern IBM mainframe? Can the CPUs still run the original 32-bit code? Do CCWs and whatever other peripheral code still work?
Intels X86S proposal[1] gives perspective on this. Both in how there would be reasons to get rid of legacy, and how yet it still got shot down pretty quickly[2]. It's unfortunate that I don't think we ever got more explanation on it's termination, where did the opposition come from
"z/Architecture retains backward compatibility with previous 32-bit-data/31-bit-addressing architecture ESA/390 and its predecessors back to the 32-bit-data/24-bit-addressing System/360."
; 0x20000 - 0x2fdff temporal space to load ; size: 63.5Kb is the max.
wasn't there an inofficial unreal mode that increased the adressable space? Otherwise there aren't too many options as to stay minimal in the first place.
I mean, if you target ancient baroque hardware like e.g. ZX Spectrum, you specifically target an ancient machine. But this is expected to work on any modern x86 hardware, while it feels like code for a 80286, and likely would run there. And this ancient stuff is still supported and actively used.