Microprocessor Chips

All microcomputer systems are driven by one or more microprocessor chips. A microprocessor chip is made up of thousands of integrated circuits that contain all of the essential elements of a central processing unit (figure 1-10). These include the control logic, instruction decoding, and arithmetic-processing circuitry.

To be useful, the microprocessor chip (which is no bigger than your fingernail) must be mounted onto what is called a carrier package (figure 1-11). This carrier package along with other chips-memory chips (RAM and ROM) and I/O integrated circuit chips\are plugged into specific socket locations on a circuit board called the system board or the motherboard (figure 1-12).

Figure 1-10.\A typical microprocessor computer chip.

Figure 1-11.\A microprocessor being mounted onto the carrier package.

Of all the boards in the microcomputer, the system board is the most important. But what are the functions of the microprocessor chip? Are all microprocessor chips designed to perform the same functions? Basically, yes; but there are some significant differences in how they perform their functions. You should be aware of these differences, especially if you will be working with several different types of micros.

A chip, is a chip, is a chip, OR IS IT? Computer chips, like everything else in data processing, have some rather unique and unusual names; names like Zilog Z-80A, Intel 80C88, MOS Technology 6502, Motorola 68000, and so on. Some chip names contain ^{letters and numbers.} Others contain only numbers.

Having the right microprocessor chip in your computer

Figure 1-12.\The system/motherboard showing placement of the microprocessor, RAM, ROM, and integrated circuit chip.

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.