MPE/iX System Utilities Reference Manual (32650-90908)

Chapter 25
STANDARDS
The initial system loader
202
The initial system loader
The Initial System Loader performs these functions:
• provides user interface with boot path information and alters boot path.
• loads an operating system-specific code set or a hardware-specific code set and launches it. If this
implementation-specific code does not damage the ISL image, ISL remains in memory in case the code
returns control to ISL for initialization of further utilities.
Certain standards are used by hardware and software operating systems using system bootstrap, IPL, and
ISL standard. These standards are architectural in nature, but are not necessarily defined in any system
architectural document. The remainer of this chapter contains a description of these standards.
Stable storage and nonvolatile memory layout
Stable storage and nonvolatile memory (NVM) are described as blocks of bytes that are accessible by
bootstrap, ISL, and the operating system through standard entry points. The first 96 bytes of stable storage
are required implementation; bytes 96 through 191 are optional, but if implemented they are reserved for
PDC and ISL access as described below. Nonvolatile memory is not required by the architecture; therefore, it
should contain only values that can be managed by an alternate method. When more than one byte is used in
the representation of an item in stable storage, the most significant byte is the byte with the lower address.
The format of stable storage is shown below:
Autoboot flags and device path
This 32-byte field defines the coldload path that PDC uses for autoboot. If this path is not valid, or if the
device that it describes is not a valid boot device containing an IPL image, PDC then requests a valid path
through the console if the console is present; otherwise, the error is displayed through the front panel.
Table 25-1 Stable storage format
BYTE CONTENTS
0-31 Boot flags and device
32-63 Unique file names
64-95 Future OS requirements
96-127 Console terminal
128-159 Alternate boot path
160-191 Dump flags and device
192-nnn Future OS options