MPE/iX System Utilities Reference Manual (32650-90882)

176 Chapter20
SAINT
PME Primary macro environment. The historical name for MPE boot images.
This document uses only the term boot image.
RFI Return from interrupt. This system instruction restores the processor
state by resetting the values of the PSW, PC space, and PC offset registers
to the values contained in the IPSW and PC space and offset queues. This
instruction can be used to switch instruction execution from real
addressing mode to virtual addressing mode.
SOM System object module. The SOM is the file used as the output of system
compilers, the input and output of the system linker and MPE/iX loader.
Its format is defined in the
SOM
Architecture Control Document
.
XRT Cross reference table. This is a process-local table built by the MPE/iX
loader, which contains information required to make intermodule
procedure calls. There is also a system XRT (SXRT) residing in system
space that is used to make system calls.
file offset A byte offset relative to the beginning of the file.
virtual offset A byte offset relative to the beginning of the space.
space offset The same as virtual offset .
Preparation for use
To bring up the operating system, the START boot image contains the code that builds the
required software structures and initializes the various components of MPE/iX, such as
the virtual space manager, memory manager, IPC, compatibility mode emulator, and so
forth.
The first code to be executed is in real addressing mode and builds the page table and hash
table required to use virtual addressing mode. It then transfers to virtual addressing mode
during the call to the virtual entry point.
When the operating system is running, some parts of it are required to be in main memory
at all times. This code is part of the system library, and is identified by the
memory-resident bit in the library's initialization pointers and subspace dictionary
entries. All code that is defined as being memory-resident is contained in the start boot
image.
The operating system code, which must reside in memory while the system is being
initialized, must also be contained in the boot image. This code is identified by the initially
frozen bit contained in the initialization pointers and subspace dictionary entries. All code
read is defined as being initially resident and is also contained in the start boot image.
During system initialization, the initially frozen code is locked in memory until the system
library is fully mapped into virtual space. At that point, the code resets to allow the
memory manager to swap it out, if necessary.
Input files
The input files accepted by the SAINT utility consist of system library files, CME files,
SXRT declaration files, and millicode files. The MPE/iX system library contains MPE/iX
system code and data structures. The system millicode is also contained in a SOM, and the
compatibility mode definition is contained in a CME file.