The Evolution of the Microprocessor

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Only once in a lifetime will a new invention come about to touch every aspect

of our lives. Such a device that changes the way we work, live, and play is a special

one, indeed. The Microprocessor has been around since 1971 years, but in the last few

years it has changed the American calculators to video games and computers (Givone

1). Many microprocessors have been manufactured for all sorts of products; some

have succeeded and some have not. This paper will discuss the evolution and history

of the most prominent 16 and 32 bit microprocessors in the microcomputer and how

they are similar to and different from each other.

Because microprocessors are a subject that most people cannot relate to and do

not know much about, this paragraph will introduce some of the terms that will be in-

volved in the subsequent paragraphs. Throughout the paper the 16-bit and 32-bit mi-

croprocessors are compared and contrasted. The number 16 in the 16-bit microproces-

sor refers how many registers there are or how much storage is available for the mi-

croprocessor (Aumiaux, 3). The microprocessor has a memory address such as A16,

and at this address the specific commands to the microprocessor are stored in the

memory of the computer (Aumiaux, 3). So with the 16-bit microprocessor there are

576 places to store data. With the 32-bit microprocessor there are twice as many

places to store data making the microprocessor faster.

Another common term which is mentioned frequently in the paper is the oscil-

lator or the time at which the processors "clock" ticks. The oscillator is the pace

maker for the microprocessor which tells what frequency the microprocessor can proc-

ess information, this value is measured in Mega-hertz or MHz. A nanosecond is a

measurement of time in a processor, or a billionth of a second. This is used to measure

the time it takes for the computer to execute an instructions, other wise knows as a cy-


There are many different types of companies of which all have their own family

of processors. Since the individual processors in the families were developed over a

fairly long period of time, it is hard to distinguish which processors were introduced in

order. This paper will mention the families of processors in no particular order. The

first microprocessor that will be discussed is the family of microprocessors called the

9900 series manufactured by Texas Instruments during the mid-70s and was developed

from the architecture of the 900 minicomputer series (Titus, 178). There were five dif-

ferent actual microprocessors that were designed in this family, they were the

TMS9900, TMS9980A, TMS9981, TMS9985, and the TMS9940. The TMS9900 was

the first of these microprocessors so the next four of the microprocessors where simply

variations of the TMS9900 (Titus, 178). The 9900 series microprocessors runs with

64K memory and besides the fact that the 9900 is a 16-bit microprocessor, only 15 of

the address memory circuits are in use (Titus, 179). The 16th address is used for the

computer to distinguish between word and data functions (Titus, 179. The 9900 series

microprocessors runs from 300 nanoseconds to 500 ns from 2MHz to 3.3MHz and

even some variations of the original microprocessor where made to go up to 4MHz

(Avtar, 115).

The next microprocessor that will be discussed is the LSI-11 which was pro-

duced from the structural plans of the PDP-11 minicomputer family. There are three

microprocessors in the LSI-11 family they are the LSI-11, LSI-11/2, and the much im-

proved over the others is the LSI-11/32 (Titus, 131). The big difference between the

LSI-11 family of microprocessors and other similar microprocessors of its kind is they

have the instruction codes of a microcomputer but since the LSI-11 microprocessor

originated from...
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