User`s guide

1.6.1 Cold Start Operation
The cold start procedure is typically executed immediately after the computer is
turned on. The cold start brings CP/M 3 into memory and gives it control of the
computer's resources. Cold start is a four-stage procedure.
In the first stage, a hardware feature, or ROM-based software associated with
system reset, loads a small program, called the Cold Boot Loader, into memory from
the system tracks of drive A (see figure 1-6). The Cold Boot Loader is usually 128 or
256 bytes long.
The Cold Boot Loader performs the second stage of the cold start process. It loads
the CP/M 3 loader program, CPMLDR, into memory from the system tracks of the
system disk and passes control to it. During this stage, the Cold Boot Loader can
also perform other tasks, such as initializing hardware dependent I/O ports.
CPMLDR performs the third stage in the cold start process. First, it reads the
CPM3.SYS file from the data area of the disk. The CPM3.SYS file, which is created
by the CP/M 3 system generation utility GENCPM, contains the BDOS and BIOS
system components and information indicating where these modules are to reside in
memory. Once CPMLDR has loaded the BDOS and BIOS into memory, it sends a
sign-on message to the console and passes control to the BIOS Cold Boot entry point.
If specified as a GENCPM option, CPMLDR can also display a memory map of the
CP/M 3 system.
CPMLDR is a small, self-contained version of CP/M 3 that supports only console
output and sequential file input. Consistent with CP/M 3's organization, it contains
two modules, an invariant CPMLDR-BDOS, and a variant CPMLDR -BIOS that is
adapted to match the host microcomputer hardware environment. Cold start initiali-
zation of VO ports and similar functions can also be performed in the CPMLDR-BIOS
module during the third stage of cold start.
In the banked version of CP/M 3, these first three stages of the cold boot procedure
are performed with Bank 0 in context. The BIOS Cold Start function switches in
Bank 1 before proceeding to stage four.
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1.6 System Operation CP/M 3 Programmer's Guide