As for Linux, Linus built it originally on x86 architecture. But it was ported to others too.

What assembly language does Linux use?

The GNU Assembler, commonly known as gas or simply as, its executable name, is the assembler used by the GNU Project. It is the default back-end of GCC. It is used to assemble the GNU operating system and the Linux kernel, and various other software.

What hardware does Linux run on?

Motherboard and CPU Requirements. Linux currently supports systems with an Intel 80386, 80486, Pentium, Pentium Pro, Pentium II, and Pentium III CPU. This includes all variations on this CPU type, such as the 386SX, 486SX, 486DX, and 486DX2. Non-Intel “clones,” such as AMD and Cyrix processors, work with Linux as well.