* Joel Sherrill: > With that in mind, what's the lowest/oldest i386 CPU model we > should consider as the new base model?
The 80486 has a CMPXCHG instruction (4-byte CAS). Starting from CAS, you can build the rest. There might be some caveats about the memory model implementation (it may not be as strongly ordered as the current i386 implementation, I haven't checked). The i386 does not have CAS, which is probably the problem you are referring to. But on non-device memory, you can certainyl fake it if you are able to disable interrupts.
