OpType.flags unused, dropped.
Speedometer doesn't guard against impossible nil.
OpType addressing, bytes, cycles are uint8, not int.
Instruction by value, not pointer. Seems ~5% faster.
cpu package extracted; Cpu, Instruction, OpType etc.
cli package extracted from go6502; Options and ParseFlags.
speedometer package extracted from go6502; Speedometer type.
go6502 package eliminated; split into new packages.