
	@(#)README 1.1 94/10/31 21:05:02

	Copyright (c) 1991 by Sun Microsystems, Inc.

	03/31/91     Roger Pham      Originated

Usage:	gtprobe [-v]

	If -v option is entered, there will be many verbose messages printed
	besides the basic messages.  If a wrong option is entered, the program
	will abort.

	This program must run on SunOS Release 4.1 or higher in superuser mode.
	Previous releases may not have the system command "/usr/etc/devinfo"
	which is used in this program to probe the SBus slots for devices and
	what they are mapped into.  The following is the general sequence of
	executions:

	- Use the system command devinfo to determine the SBus slots that are
	  having hardware device on them.

	- Check if a 'gt' device is found upon executing.  If so, proceed to 
	  the next step.  If not, it would default to the first unoccupied
	  SBus slot; unless, all three slots are occupied in which case the
	  program will have to abort.

	- Open the device that user had selected (/dev/sbus1, /dev/sbus2, or
	  /dev/sbus3) and map in the address.

	- Read the HSA Mode Register.  If a timeout occurs which would result
	  a bus error or the system would hang, the HSA is put or specified
	  within the realm of this program the wrong SBus slot.  Otherwise,
	  the program proceeds to toggle mode bits inside this register by
	  writting and reading back to verify.

	- Read the MIA Test Register.  If a timeout occurs which would result
	  a bus error or the system would hang, the GT is unconnected, not
	  powered, or a bad cable. Assert a hold to the FE Hold Register.
	  This is to prevent the FE from executing and might overwrite the
	  content of the MIA Test Register.  After that, write the test
	  patterns to the Test Register and read each one back for verification.

	- Read the entire OpenBoot PROM, except for the last 4 bytes because
	  this is the checksum of the PROM.  Add all the bytes up to form
	  a calculated checksum.  Verify this calculated checksum with the
	  checksum that is deposited in the last location of the Openboot PROM
	  and see if they match.  If there is a mismatch, the OpenBoot PROM
	  is bad.
