Motherboard or Backplane Designed Computer Frames/Cabinets

Subassembly or pcb mounting slides and retaining hardware Subassembly or pcb electrical connector receptacles and interconnecting wiring harness Printed circuit boards External connections for data and power cables An operator’s control or maintenance panel Power supply unit Blower unit Air filter In a cage or rack arrangement, only the functional areas of the computer are contained in the cage or rack. The cage or rack contains pcb’s that only house the major functional areas, such as CPU, memory, and I/O. Sometimes more than one functional area will be contained on a pcb. The pcb’s slide into slots inside the cage or rack. The connector receptacles for each subassembly or pcb are usually located at the rear of the cage or rack. The pcb’s are not always keyed, so you must exercise care when installing them. The pcb’s are secured in each slot by retaining hardware. The cage or rack is generally fixed and cannot be extended as a whole unit. The pcb’s can usually be accessed with power on, but power must be secured when you remove and replace a pcb. The pcb’s can be extended individually for maintenance. The other main parts of the computer, such as the power supply unit and cooling unit, are located in a different part of the frame or cabinet, not in the cage or rack with the pcb’s. Figure 2-12 is an illustration of a cage or rack setup. Motherboard- or Backplane-Designed Computer Frames/Cabinets Computers that use a motherboard or backplane design are built more for their portability and compactness. They are the least rugged. The frame or cabinet contains the following: A motherboard or backplane with the connector receptacles for each pcb, the keyboard, and in some types of micros: single inline memory modules (SIMMs), single inline packages (SIPS), and single inline pin packages (SIPPs) Wiring harness for the motherboard or backplane Pcb’s with the necessary I/O connectors External connections for the power cables Retaining hardware for the motherboard or backplane A power supply unit A small fan with an air filter for cooling A small speaker Figure 2-12.—Example of a cage- or rackdesigned computer frame or cabinet. 2-11