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Reading Stable Storage Contents

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Stable storage contains the boot path information along with other critical file system parameters in a minimum area of 96 bytes of high-reliability memory. The storage maintains the critical parameters even if the storage card is removed from the backplane. After the initial memory controller is initialized, the processor-dependent code (PDC) accesses stable storage to determine the boot device and console selection process.

The stable storage contents are allocated as shown in Figure C-1 Stable Storage Contents.

Figure C-1 Stable Storage Contents

[Stable Storage Contents]

NOTE: Byte addresses are numbered beginning with 0. For example, 0 is the first byte, 1 is the second.

Decimal byte address 0 contains the status of the autoboot and autosearch flags. The byte contains two hexadecimal values. The first two binary digits of the first value show the flag status as either ON (1) or OFF (0). Byte 7, obtained by reading decimal address 4, contains the logical module index.

The console path and alternate paths are stored in the same format as the primary boot path. Unlike the primary boot path, the first byte of the first word of the console and alternate boot paths is set to hex 00. The autoboot and autosearch flags are not stored with these paths.To read one word (4 bytes) of stable storage, use the ISL command READSS: 

  ISL> READSS x Return
or 

  ISL> READSS Return

        Input SS address: 4

        Address 4 contains 0x00000200



Appendix C Reading Stable Storage and Nonvolatile Memory

Reading Nonvolatile Memory (NVM)