Microprocessors Evolution
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- cle. 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 the

PDP-11 family it is a multi-microprocessor (Avtar, 207). The fact that the

LSI-11 microprocessor is a multi-microprocessor means that many other mi-
croprocessors are used in conjunction with the LSI-11 to function properly (Avtar,

207). The LSI-11 microprocessor has a direct processing speed of 16-bit word and

7- bit data, however the improved LSI-11/22 can directly process 64-bit data
(Titus, 131). The average time that the LSI-11 and LSI-11/2 process at are 380
nanoseconds, while the LSI-11/23 is clocked at 300 nanoseconds (Titus, 132).

There are some great strengths that lie in the LSI-11 family, some of which are
the efficient way at which the microprocessor processes and the ability to run
minicomputer software which leads to great hardware support (Avtar, 179).

Although there are many strengths to the LSI- 11 family there are a couple of
weaknesses, they have limited memory and