operations vector; promops pointer passed to programs run by "boot" cmd;

	struct promops {
		char magic[4];
		int prom_version;
		int promops_version;
		int promops_size; /* init with sizeof(struct promops) */

		int nops;	  /* init with N_OPS */
		int (*ops[N_OPS])();
*OR*
		int (*op_halt)(int autoboot);
		int (*op_reboot)(char *str);
		int (*op_command)(char *);	/* eval command */
		int (*op_break)(void);	/* drop into monitor */
		int (*op_set_breakpoint)(int breakn, void *addr);
		int (*op_clear_breakpoint)(int breakn, void *addr);
		int (*op_set_sync_hook)(int (*synchook)(void));
	};

add "sync" command

add support for parity/NMI