I think there are three reasons: one is that the code my compiler backend produces is "ok" but not fantastic (though it's somewhat better now than it was when t

I think there are three reasons: one is that the code my compiler backend produces is "ok" but not fantastic (though it's somewhat better now than it was when that article was written) - another is that I have only 8 registers, and only five are available for the code generator to play with, so I have to spill registers onto the stack sooner than more register-rich ISAs - and finally my simplistic 8-bit instructions don't do as much as a RISC ISA's 16-bit instructions, so some of the advantage of them being only a single byte is lost.