system makes all the difference in the world in terms of
internal processing speeds (33MHz, 66MHz,
120MHz, and so on), number of bits handled (8, 16, or
32 bits), memory size (640K, 4M, 16M, and up), and
the applications software it will run.
Each microcomputer contains a specific
microprocessor chip as its main processor. A
microprocessor chip can typically handle 8, 16, or 32
bits of information at once. Generally speaking, the
more bits a computer can manipulate at one time, the
faster it can process program instructions and data, and
the larger the main or primary memory it can
accommodate. The type of chip in your computer or
system unit also has a great effect on what you can do
with your micro. For example, operating systems are
written to serve a specific microprocessor chip, and
applications programs that work under one operating
system are not likely to work under another unless the
program is modified. Many applications programs
come in several versions to provide compatibility with
several operating systems.
These are just a few of the reasons why we say it is
very important that you read all the documentation
that comes with your microcomputer. The Navy uses
many different types of microcomputers and
microprocessor chips.
To give you an idea of the
variety, table 1-1 lists some of the microprocessor chips.
Specialized Processors
Specialized processor chips have been developed to
shift some of the workload from the main
Table 1-1.—Microcomputer Chips and Microcomputers
microprocessor chip. For example, IBM uses an Intel
8048 chip on the keyboard to determine which keys are
being depressed and also to check to see that the
keyboard is communicating properly with the
microprocessor. In fact, most peripheral devices have
one or more specialized processors embedded in them.
Other specialized processors are the Intel 80287
and the faster 80387 math coprocessor. These are
special-purpose programmable microprocessors
designed to perform arithmetic calculations up to 100
times faster than the main microprocessor. A math
coprocessor executes arithmetic instructions that would
normally be handled by the main microprocessor’s
arithmetic-logic unit (ALU) as well as those the main
microprocessor cannot perform because of register
constraints. The 80287 and 80387 are companion chips
to the Intel family of microprocessors. Computer
systems using the 80 series of chips are capable of very
high-speed mathematical operations when the math
coprocessor chip is plugged either into or alongside the
system or motherboard. Math coprocessor chips are
used in SX version computers. The SX denotes that the
computer does not have a math coprocessor integrated
into the cpu chip. A DX version computer has a math
coprocessor integrated into the cpu chip. With the
development of the Pentium chip, math coprocessor
chips were no longer required to perform arithmetic
calculations.
INPUT/OUTPUT DEVICES AND
ACCESSORIES
To the system unit we must add input/output
devices to communicate between us and the computer.
These include the monitor, the keyboard, disk drives,
and the printer. We will look at each of these devices in
the following sections, along with some of the more
common accessories found on microcomputers, such as
surge protectors, parallel to serial converters and vice
versa, null modems, cables, and switches used for
sharing hardware.
Monitors (Display Devices)
Monitors are used as output devices on
microcomputers.
They are peripheral devices that
contain a display like a television viewing screen. They
are the principal link between you and the
microcomputer. Their sole purpose in life is to allow the
microcomputer to communicate its actions to you (the
user), so you can act upon those actions to accomplish
whatever job you are doing. They display output from
the computer. The monitor is one of the most important
peripherals to a micro and is certainly the most visible.
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