size of the frame or cabinet of a computer is a general
indication of the type of computer and the type of data
system the computer is used on. Consult your
computer’s technical manual or owner’s manual for
parts, tools, and test equipment needed in the
maintenance of the computer.
Let’s take a look at the designs or types of
frames/cabinets—modular, chassis or assembly, cage or
rack, and motherboard or backplane. Some computers
use combinations of these designs.
Modular-Designed Computer Frames/Cabinets
A frame or cabinet of modular design uses the
concept that a functional area maybe composed of one
module or several modules. An example of several
modules that comprise one functional area is memory.
It may take four modules to make up one functional
area, memory. Modular frames or cabinets contain the
following:
External connections for data, control, and I/O
cables
Modules with test blocks on some types of
computers
Module mounting slides and retaining hardware
Module electrical connector receptacles and
interconnecting wiring harness
An operator’s control panel
A blower unit and a system of air ducts allowing
cooling air to circulate through all module heat
exchangers
Gaskets for electronic shielding, moisture
protection, air ducting, and electrical connectors
Filters for electronic shielding
Each module is made up of subassemblies and/or
pcb’s and a heat exchanger for air-to-air cooling.
Modular-designed computers that are watercooled will
have the necessary hardware fixtures for liquid cooling.
A maintenance panel can be located up to 15 feet from
the frame or cabinet that houses the functional areas or
it may be affixed over the top of the frame or cabinet.
In the modular setup, the power supply will be
contained in a module just as the major functional areas
are. Figure 2-10 is an illustration of a modular setup
used in a large mainframe computer.
The modular-designed frame or cabinet is the most
rugged. Each module fits into a compartment. The
modules slide into the compartments of the frame or
cabinet and are secured with retaining hardware to
prevent the module or assembly from sliding back out.
At the rear of each compartment of the frame or cabinet
for each module, there is an electrical connector
receptacle for data and power. The receptacle is keyed
so the module can only go in one way. You must secure
the power when removing and replacing a module or to
gain complete access to all the subassemblies or pcb’s
inside a module.
Each module contains all the electronic parts and
circuitry that make up one functional area or a portion
of a functional area. Examples of modules used in a
modular design of a large mainframe computer are the
CPU, I/O, memory, and power supply. The CPU
usually consists of only one module, whereas the
memory of a computer may require multiple modules
to form the memory.
Each module will consist of
electronic subassemblies and/or printed circuit boards
that are color coded for easy identification. The printed
circuit boards will fit into keyed slots that are in close
proximity to each other. In this way one module can
hold over 200 pcb’s. The pcb’s are configured in rows.
Check the computer’s technical manual for the chassis
map of the pcb’s and other major subassemblies. Refer
back to figure 2-9 for an illustration of a module with
the cover removed.
Other items found on a module are test blocks for
maintenance, a time meter to monitor powered-on time,
gaskets for electronic shielding, and a heat exchanger
for cooling. The functional areas that are basic to most
modularly designed computers include the following:
Central processing unit (CPU)
Input/Output controller (IOC)
Input/Output adapter (IOA)
Memory
Power supply
Chassis- or Assembly-Designed Computer
Frames/Cabinets
The design concept of computers that use the
chassis or assembly arrangement is for the whole
computer system to be located on one or more chassis
or assemblies.
Chassis- or assembly-designed
computers are smaller than modular frame or cabinet
housed computers, but they are also very rugged.
2-8
