Yes Dynarec is platform specific but i have written one for x86 processors and have designed it so that the amount of code that need to rewritten to port it for other processors is limited as much as possible. Unfortunately it's not usable yet.
There will also be a fast interpreter that will be something like a compiler written in c (actually it's more an opcode cache but i'm very confident that it'll speed things up much and it'll work on all systems)