IBM 5150 Hardware Reference Manual

The FOe is capable of performing 15 different commands. Each
command is initiated by a multi-byte transfer from the processor, and
the result after execution of the command may also be a multi-byte
transfer back to the processor. Because ofthis multi-byte interchange
of
information between the FOe and the processor, it is convenient to
~ consider each command as consisting of three phases:
Command Phase
The
FDC receives all information required to perform a particular operation
from the processor.
Execution Phase
The FOe performs the operation it was instructed to do.
Result Phase
After completion of the operation, status and other housekeeping
information are made available to the processor.
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IBM 5150 Specifications

General

Processor	Intel 8088
Clock Speed	4.77 MHz
RAM	16 KB - 256 KB
Manufacturer	IBM
Model	5150
Release Year	1981
Storage	5.25-inch floppy drives
Graphics	MDA or CGA
Operating System	IBM PC DOS
Ports	Cassette, keyboard
Expansion Slots	5