System Startup, Configuration, and Shutdown Reference Manual (32650-90892)

30 Chapter2

Initiating System Activity

Determining and Selecting Input and Output (I/O) Paths

The system identiﬁes adapter interfaces to a system bus and the associated devices by an

I/O path. The I/O path is the address of the interface hardware and the physical path to

reach a device.

When the system is reset or the power is turned on, hardware routines read and initialize

the I/O paths needed to boot the system. These boot paths consist of the primary boot path,

for booting from disk-resident software; the alternate boot path, for booting from a system

load tape; and the console boot path, for locating console operator intervention.

Boot paths for the primary boot device, the alternate boot device, and the console are

shown as numbers separated by periods or forward slashes.

There are several ways to determine the I/O path for devices that are attached to the

system:

• Generate a list of paths for devices that have already been conﬁgured by using the

LPATH command of the SYSGEN utility IO Conﬁgurator. SYSGEN does not tell you if

the conﬁgured device is active or available. During the system boot (using the ISL

START command), information on which paths have been conﬁgured and which devices

are available or not available is listed as the “System State at Boot Time.” (For more

information on the system state, refer to Chapter 3 , “System Startup Functions,” and

Appendix B , “Startup, Dump, and Shutdown Listings.” For more information on

SYSGEN, refer to Chapter 4 , “Using the System Generator (SYSGEN).”)

• Use the ISL utility, IOMAP, to list the devices on the system. (For more information on

IOMAP, refer to Appendix E , “Verifying Attached Devices.”) For 9X8LX and 9X8RX

systems, use the ODE utility to list devices on the system.

• For the N-class and A-class systems, the BCH (Basic Console Handler) SEA command

in the Main Menu lists the disk and tape devices physically present on the system.