	System configuration overview
	------ ------------- --------

Purpose of new configuration support:
	
	* Provides a way to detect inoperative components of the
	  system which don't respond to software probing.

	* Allows a user to explicitly configure out broken components 
	  without having to physically remove them from the machine.

	* Assists FE's by allowing them to configure out components
	  during diagnostic process.


Implementation:

/*
 * Hardware configuration data structure. This information is
 * saved in NVRAM so that the PROM can check the system for unintended
 * changes to the configuration.
 */

typedef struct {
        uchar     cf_status;            /* Status info for this unit */
        uchar     cf_diagval;           /* Return value from diags */
        ushort    cf_pad;               /* Leftover space */
} config_t;

typedef struct {
        uchar     bcf_class;            /* Class containing this board */
        uchar     bcf_type;             /* Type of board */
        ushort    bcf_rev;              /* Board's revision level */
        config_t  bcf_status;           /* Status of global board-level logic */
        config_t  bcf_unit[CFG_MAXUNITS]; /* Status of units on board */
} brdconfig_t;


	The NVRAM contains a brdconfig structure for each of slots
	in the tfp backplane.  When a new device is recognized,
	the brdconfig structure for it is initialized based on its
	class (IO, MEM, CPU) and type (IO4, IP19, IP21, MC3).  
