Service manual

Using boot code stored in its EEPROM, the boot processor reads the boot

block from a speciﬁed device. Booting may be triggered by a command

issued to the boot processor from the console, or by a system reset with the

bottom key switch in the Auto Start position.

The boot processor also communicates with the system console, using

the common console lines on the backplane. When you change system

parameters in the EEPROM using SET commands, the boot processor

automatically copies the new values to the EEPROMs on the secondary

processors. If you swap in a new <REFERENCE>(xyp) module, it should be

conﬁgured as a secondary processor. Then you can either use the UPDATE

command to copy the boot processor’s entire EEPROM to the new secondary

or use EVUCA and a series of SET commands to customize the EEPROM.

Since UPDATE is slow, and can, in certain instances, render a processor

unusable, the preferred method of updating a new processor placed in a

system is to do it using SET commands. See Section 3.15 for information

on running EVUCA and Section 3.12.2 on setting parameters.

CAUTION: Using UPDATE can be dangerous because of revision

mismatches. See Appendix C for information on what happens in

mismatched cases.

Usually the processor with the lowest <REFERENCE>(XMI) node number

(which is also the lowest slot number) is selected as the boot processor.

However, if this processor does not pass all its power-up tests, the next

higher-numbered processor is selected. This is one way the boot processor

can change.

The user also has control over boot processor selection with the SET CPU

command. This command may declare a processor ineligible for selection.

SET CPU can also select a boot processor explicitly.

You can see the boot processor selection three ways:

• In the self-test display, the boot processor is indicated by a B on lines

labeled BPD.

• In console mode, the command SHOW CPU displays the boot processor

as "Current primary."

• In program mode, the bottom red LED (next to the larger yellow LED)

is off on the boot processor module. It is lit on secondary processors.

<REFERENCE>(xyp) Scalar Processor 3–11