Microprocessors


Inside of the mysterious box that perches ominously on your desk is one of
the marvels of the modern world. This marvel is also a total enigma to most of
the population. This enigma is, of course, the microprocessor. To an average
observer a microprocessor is simply a small piece of black plastic that is found
inside of almost everything.
In How Microprocessors Work they are defined as a computer\'s central
processing unit, usually contained on a single integrated circuit (Wyant and
Hammerstrom, 193). In plain English this simply means that a microprocessor is
the brain of a computer and it is only on one chip. Winn L. Rosch compares them
to being an electronic equivalent of a knee-joint that when struck with the
proper digital stimulus will react in the exact same way each time (Rosch,37).
More practically a microprocessor is multitudinous transistors squeezed onto as
small a piece of silicon as possible to do math problems as fast as possible.
Microprocessors are made of many smaller components which all work
together to make the chip work. A really good analogy for the way the inner
workings of a chip operate can be found in How Microprocessors Work. In their
book, Wyant and Hammerstrom describe a microprocessor as a factory and all of
the inner workings of the chip as the various parts of a factory (Wyant and
Hammerstrom, 71-103). Basically a microprocessor can be seen as a factory
because like a factory it is sent something and is told what to do with it. The
microprocessor factory processes information. This most basic unit of this
information is the bit. A bit is simply on or off. It is either a one or a zero.
Bits are put into 8 bit groups called bytes. The number 8 is used because it is
offers enough combinations to encode our entire language (2^8=256). If only 4
bits are used only (2^4=16) combinations would be possible. This is enough to
encode 9 digits and some operations. (The first microprocessors powered
calculators) A half byte is called a nibble and consists of 4 bits. In the world
of computer graphics the combination of bits is easier seen. In computer
graphics bits are used to make color combinations, thus with more bits more
colors are possible. Eight bit graphics will display 256 colors, 16 bit will
display 65,536, and 24 bit graphics will display 16.7 million colors. The bus
unit is described as the shipping dock because it controls data transfers, and
functions between the individual pieces of the chip. The part of the chip that
performs the role of a purchasing department is called the prefetch unit. It\'s
job is to make certain that enough data is on hand to keep the chip busy. The
decode unit performs the role of a receiving department. It breaks done
complicated instructions from the rest of the computer into smaller pieces that
the chip can manipulate more readily. The control unit is compared to the
person who oversees the workings of the entire factory. It is the part of the
chip that keeps all the other parts working together and coordinates their
actions. The arithmetic logic unit is compared to the assembly line of the
factory. It is the part of the microprocessor that performs the math operations.
It consists of circuitry that performs the math and the registers which hold the
necessary information. The memory management unit is likened to the shipping
department of this digital factory. It is responsible for sending data to the
bus unit. Together all of the individual pieces support each other to make this
digital symbiosis work as fast as possible.
To an outsider, computer nerd vernacular and all other forms of computer
people esoteric may or may not be considered frightening. Probably the most
confused term in microprocessor performance is Megahertz (MHz). Basically these
are millions of cycles per second. This is a measurement of chip speed but is
better considered the RPM of the chip (Knorr, 135). For example a 486 100 MHz
processor cannot touch the speed of a Pentium running at only 60 MHz. This is
because the Pentium packs more power and can do more per clock cycle. The
computer bus is the data line that connects the microprocessor the rest of the
computer. The width of the bus (how many bits it consists of) controls how much
data can be sent to the chip per clock cycle. MIPS or millions of instructions
per second is simply how many instructions the chip can perform in one second
divided by 1,000,000. RISC is a