[Locutus_]

M68k has the advantage that it has a fairly typical memory model.

Alpha's memory model has problems with providing atomic access to single bytes, which i'd imagine in a kernel is a bit annoying :-)

And then there's just the social aspect, m68k was used in the Amiga/Atari/Mac/QL/x68k, so there is a whole generation of us m68k fans who are willing to keep it alive.

Alpha has it's fans (me included!), but it's not exactly the same. So in a way it's no surprise it's slowly bitrotting away.

[starspangled]

Since the C compiler can hide that, for core kernel code I think the more problematic thing was Alpha's memory consistency model where (data-)dependent loads accesses did not imply ordering, which is unusual and more burdensome to the programmer than any other ISA.

That required this smp_read_barrier_depends() through the kernel, but actually in recent years that has basically been subsumed by other concurrent access primitives that all the core kernel must use, so I think alpha is no longer much of a problem outside arch/alpha

[winocm]

Ah, my favorite instructions, 'hw_ldl/l', 'hw_stl/c', 'ldl_l', 'stl_c' and their quadword siblings.