In a microcomputer system, the central processing unit (CP) or processor is contained on a single chip called the microprocessor. The microprocessor is the “brains” of the computer system. It has two basic components: the control unit and the arithmetic-logic unit.
- Control unit: The control unit tells the rest of the computer system how to carry out a program’s instructions. It directs the movement of electronic signals between memory, which temporarily holds data, instructions, and processing information, and the arithmetic-logic unit. It also directs these control signals between the CPU and input and output devices.
- Arithmetic-logic unit: The arithmetic-logic unit, usually called the ALU, performs two types of operations: arithmetic and logical. Arithmetic operations are, as you might expect, the fundamental math operations: addition, subtraction, multiplication, and division. Logical operations consist of comparisons. That is, two pieces of data are compared to see whether one is equal to (=), less than (<), or greater than (>) the other.
Chip processing capacities are often expressed in word sizes. A word is the number of bits (such as 16, 32, or 64) that can be accessed at one time by the CPU. The more bits in a word, the more data a computer can process at one time. As mentioned previously, eight bits group together to form a byte. A 32 bit-word computer can access 4 bytes at a time.
A 64-bit-word computer can access 8 bytes at a time. Therefore, the computer designed to process 64-bit words is faster. Other factors affect a computer’s processing capability including how fast it can process data and instructions.
The processing speed of a microprocessor is typically represented by its clock speed which is related to number of times the CPU can fetch and process data or instructions in a second. Older microcomputers typically process data and instructions in millionths of a second, or microseconds.
Newer microcomputers are much faster and process data and instructions in billionths of a second, or nanoseconds. Supercomputers, by contrast, operate at speeds measured in picoseconds-1,000 times as fast as microcomputers.
Logically the higher a microprocessor’s clock speed, the faster the microprocessor. However, some processors can handle multiple instructions per cycle or tick of the clock; this means that clock speed comparisons can only be made between processors that work the same way.
The two most significant recent developments in microprocessors are the 64-bit processor and the multicore chip. Until recently, 64-bit processors were only used in large mainframe and supercomputers. All of that is changing as 64-bit processors have become standard for most of today’s desktop and laptop computers.
Intel Atom TM processor is Intel’s smallest processor built with the world’s smallest transistor. 45nm Intel AtomTM processor has 47 million transistors on a single chip measuring less than 26 mm².
The other recent development is the multicore chip. As mentioned previously a traditional microcomputer’s CPU is typically contained on a single microprocessor chip. A new type of chip, the multicore chip, can provide two or more separate and independent CPUs.
These chips allow a single computer to run two or more operations at the same time. For example, a dual-core process could have one core computing a complex Excel spreadsheet while the other is running a multimedia presentation. More significantly, however, is the potential for microcomputers to run very large, complex programs that previously required expensive and specialized hardware.
For multicore processors to be used effectively, computers must understand how to divide tasks into parts that can be distributed across each core-an operation called parallel processing. Operating systems such as Windows Vista and Mac OS X support parallel processing. Software developers use this technology for a wide range of applications from scientific programs to sophistical computer games.