Modular-Designed Computer Frames/Cabinets

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