I very successfully built a "truly-compiled FORTH" on a 6502 machine – it actually generated subroutines – and I know that there were several TIL-based dialects for it also. Although the 6502 had some rather unique addressing capabilities, the fact that it only had three CPU registers and that two of them were only for addressing meant that it usually took quite a few more instructions to do things vs. other chips like the Z-80. Not what you want when you've only got 64K.