Yes, if the 128 of the 6537 is mapped starting at 0x100, then one would use ldx, txs, pha, pla, etc., for any possible optimization. S register is a precious re

Yes, if the 128 of the 6537 is mapped starting at 0x100, then one would use ldx, txs, pha, pla, etc., for any possible optimization. S register is a precious resource! Anything to squeeze between those hsyncs.