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CPIM-86 System Overview
1-4
CP/M-80 AND CP/M-86 DIFFERENCES
The structure of CP/M-86 is as close to CP/M-80 as possible. This provides a
familiar programming environment which allows application programs to be
transported to the 8086 processor with minimal effort. This section points out
specific differences between CP/M-80 and CP/M-86 to reduce your time in scan-
ning the manual if you are already familiar with CP /M-80. The terms and concepts
presented in this section are explained in detail throughout the manual, so refer to
the Table of Contents for the relevant chapters which provide specific definitions
and information.
Relocatable Groups
The fundamental difference between CP/M-80 and CP/M-86 is found in the
management of the various relocatable groups. Although CP/M-80 references
absolute memory locations by necessity, CP /M-86 takes advantage of the static
relocation inherent in the 8086 processor. The operating system itself is loaded
directly above the interrupt locations, at location 0400H, and relocatable transient
programs load in the best fit memory region. However, you can load CP /M-86 into
any portion of memory without changing the operating system (thus, there is no
MOVCPM utility with CP /M-86), and transient programs will load and run in any
non-reserved region.
Memory Models
CP/M-86 is constructed as an 8080 Model. This means that all the segment registers
are placed at the base of CP/M-86, and the CBIOS is identical in most respects to
that of CP IM-80 (with changes in instruction mnemonics, of course). In fact, the
only additions are found in the SETDMAB, GETSEGB, SETIOB, and GETIOB
entry points in the BIOS, the additions for hard disk I/O, and the custom APC
features in the extended functions. The warm start subroutine is simpler since you
are not required to reload the CCP and BDOS under CP/M-86. If you implement
the IOBYTE facility, you have to define the variable in your BIOS. Taking these
changes into account, you need only perform a simple translation of your CP/M-80
BIOS into 8086 code to implement the 8086 BIOS.
Disk Definition Tables
The disk definition tables included with CP /M-86 for the APC have been deve-
loped, configured, and included in the CBIOS. Therefore, there is no need to
generate your own disk definition tables using GENDEF.
Bootstrap Operation
CP/M-86 resides on the first two tracks of the double-sided, double-density system
distribution diskette. It is loaded by a single step bootstrap loader operation.
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