using the bootstrap loader

1.2 THE STAGES OF THE BOOTSTRAP LOADER
OVERVIEW OF BOOTSTRAP LOADER OPERATIONS
The Bootstrap Loader has a number of stages that control the loading of the application
system. iRMX I applications load with a two-stage process. iRMX II applications use
these two stages but also require a third stage.
1.2.1 First Stage
The Bootstrap Loader's first stage consists of two parts. One part is the code for the first
stage. The other part is a set of minimal device drivers used by the first and second stages
to initialize and read from the device that contains the system to be booted.
The Bootstrap Loader package contains device drivers for many common Intel devices. To
support other devices, you can write your own drivers and configure them into the first
stage.
To use the Bootstrap Loader, the first stage must be in one of two places. The natural
place for the first stage is in PROM devices, either as a standalone product or combined
with a monitor. Intel 300 Series Microcomputers are delivered with the Bootstrap
Loader's first stage, the iSDM monitor, and the System Confidence Test (SCT) in the
PROM devices.
When the first stage begins running, it first identifies the bootstrap device and the name of
the file to boot. It can identify the device from a command line you enter at the monitor,
or it can use default characteristics established when the first stage was configured. The
Bootstrap Loader then calls its internal device driver for the device, to initialize the device
and read the first portion of the second stage into memory. This occurs for all devices
except when the device is located in a remote system (for example, over a Local Area
Network). After calling the internal device driver, the first stage passes control to the
second stage. When the bootstrap device is a remote device, the remote system does not
load the second stage.
Debugging the First Stage
Because the first stage works on both 8086/186- and 80286/386-based computers, it
operates in real address mode when running in an 80286/386-based system. This means
that any device drivers you write for the first stage must operate in real address mode.
If you have a system that includes the iSDM monitor and you are adding your own device
driver to the Bootstrap Loader's first stage, you will find it useful to load the first stage into
the target system's RAM using a development system iSDM loader. Then you can activate
the first stage under iSDM control from the development system. After activating the first
stage, you can then debug driver code.
Bootstrap Loader 1-3