pdc(1M)

Server Behavior

To load isl from an external medium, pdc must know the particular device on which isl resides. Typically the device is identified by the Primary Boot Path that is maintained by pdc in Stable Storage. A path specification is a series of decimal numbers each suffixed by '/', indicating bus converters, followed by a series of decimal numbers separated by '.', indicating the various card and slot numbers and addresses. The first number, not specifying a bus converter, is the MID-BUS module number (that is, slot number times four) and followed by the CIO slot number. If the CIO slot contains a terminal card, the next number is the port number, which must be zero for the console.

When the processor is reset after initialization and self-test complete, pdc reads the Console Path from Stable Storage, and attempts to initialize the console device. If the initialization fails, pdc attempts to find and initialize a console device. Algorithms used to find a console device are model-dependent. pdc then announces the Primary Boot, Alternate Boot, and Console Paths.

If autoboot (see isl(1M)) is enabled, pdc provides a 10-second delay, during which time the operator can override the autoboot sequence by typing any character on the console. If the operator does not interrupt this process, pdc initializes and reads isl from the Primary Boot Path. On models that support autosearch, if this path is not valid and autosearch (see isl(1M)) is enabled, pdc then searches through the MID-BUS modules and CIO slots to find a bootable medium. Currently, autosearch is only implemented on the model 825.

If the autoboot sequence is unsuccessful, overridden by the operator, or not enabled in the first place, pdc interactively prompts the operator for the Boot Path to use. Any required path components that are not supplied default to zero.

The Primary Boot, Alternate Boot, and Console Paths as well as autoboot and autosearch enable can be modified via isl.

Workstation Behavior

To load isl from an external medium, pdc must know the particular device on which isl resides. Typically the device is identified by the Primary Boot Path that is maintained by pdc in Stable Storage. A path specification is an I/O subsystem mnemonic that varies according to hardware model.

When the processor is reset after initialization and self-test complete, pdc reads the Console Path from Stable Storage, and attempts to initialize the console device. If the initialization fails, pdc attempts to find and initialize a console device. Algorithms used to find a console device vary according to hardware model.

If autoboot and autosearch (see isl(1M)) are enabled, pdc waits for approximately 10 seconds during which time the operator can override the autoboot sequence pressing and holding the ESC (escape) key on the console.

The system then begins a search for potentially bootable devices. If allowed to complete, a list of potentially bootable devices is displayed, labeled with abbreviated path identifiers (P0, P1, etc). A simple menu is then displayed where the user can:

The search of potentially bootable devices can be aborted by pressing and holding the escape key. The search for device contents can also be aborted by pressing and holding the escape key.

If the operator does not interrupt the search process, pdc initializes and reads isl from the Primary Boot Path.

If the autoboot sequence is unsuccessful, overridden by the operator, or not enabled in the first place, pdc executes the device search and enters the menu described above.

The Primary Boot, Alternate Boot, and Console Paths as well as autoboot and autosearch enable can be modified via isl or at the pdc boot administration level.