FREE ESSAY ON MICROPROCESSOR

MICROPROCESSOR

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 the slow- ness of speed at which the LSI-11 processes at (Avtar, 179). The
next major microprocessors in the microcomputing industry were the Z8001 and Z8002,
however when the microprocessor entered into the market the term Z8000 was used to mean
either or both of the microprocessors (Titus, 73). So when describing the features of
both the Z8001 and the Z8002, they will be referred to as the Z8000. The microprocessor
was designed by the Zilog Corporation and put out on the market in 1979 (Titus, 73). The
Z8000 are a lot like the many other previous micro- processors except for the obvious
fact that it is faster and better, but are similar be- cause they depend on their
registers to function properly (Titus, 73). The Z8000 was improved by using 21 16-bit
registers, 14 of them are used for general purposes opera- tions (Titus, 73). The
difference with the Z8001 and the Z8002 is the Z8002 can only address 65K bytes of
memory, which is fascinating compared to the microprocessors earlier in time but is
greatly inferior to the Z8001 which can address 8M bytes (8000K) of memory (Titus, 73).
The addressing memory between the two otherwise very simi- lar microprocessors is
drastically different were as other functions of the microproces- sors seem to be quite
the same. An example of this is the cycle time. The cycle time is 250 nanoseconds and the
average number of cycles that occur per instruction are be- tween 10 and 14 for both
microprocessors (Avtar, 25). The next microprocessor that will be discussed is the 8086.
This microproces- sor is the best in my opinion, out of all the 16-bit microprocessors.
Not only because the speeds of processing are tremendous, but because it simply paved the
way to the 32-bit microprocessors using various techniques that will be discussed later.
The 8086 was the second Intel microprocessor (being preceded by the 8080) (Avtar, 19).
The 8086 was introduced in early 1978 by Intel (Avtar, 19). Like so many of the other
processors the 8086 is register oriented with fourteen 16-bit registers, eight of which
are used for general processing purposes (Avtar, 19). The 8086 can directly address 1MB
(1,048,576 bytes) which is used only in accessing Read Only Memory. The ba- sic clock
frequency for the 8086 is between 4MHz and 8MHz depending on the type of 8086
microprocessor that is used (Avtar, 20). Up until this point in the paper there have been
common reoccurring phrase such as a microprocessor containing 14 16-bit registers. At
this time in the evolution of microprocessors come the 32-bit register, which obviously
has double the capacity to hold information for the microprocessor. Because of this
simple increase of the register capacity we have a whole different type of
microprocessor. Although the 16- bit and 32-bit microprocessors are quite different
(meaning they have more compo- nents and such), the 32-bit microprocessors will be
described in the same terms as the 16-bit microprocessors were. The remainder of the
paper will discuss the 32-bit microprocessor series. The external data bus is a term that
will be referred to in the remainder of the paper is. The data bus is basically what
brings data from the memory to the processor and from the processor to the memory
(Givone, 123). The data bus is similar to the registers located on the microprocessor but
are a little bit slower to access (Givone, 123). The first 32-bit microprocessor in the
microprocessor industry that will be dis- cussed is the series 32000 family and was
originally built for main-frame computers. In the 32000 family all of the different
microprocessors have the same 32-bit internal structure; but may have external bus values
such as 8, 16, or 32 bits (Mitchell, 225). In the 32000 family the microprocessors use
only 24 of the potential 32 bit addressing space, giving the microprocessor a 16 Mbyte
address space (Mitchell, 225). The 32- bit registers are set up so there are six 32-bit
dedicated registers and then in combina- tion there are two 16-bit dedicated registers
(Mitchell, 231). Each dedicated register has its own type of specific information that it
holds for processing (Mitchell, 232). The microprocessors oscillator (which now comes
from an external source) runs at 2.5 MHz, but due to a "divide-by-four prescaler" the
clock frequency runs at 10MHz. There have been many new ideas put into practice to
improve the 32000 series micro- processor generally and thus making it run faster and
more efficient. The next family of microprocessor which was fabricated for the
microcomputer is the MC68020 32-bit microprocessor which is based on the MC68000 family.
The other microprocessors that are included in this family are the MC68000, MC68008,
MC68010 and the MC68012 (Avtar, 302). Before going into the types of components that this
microprocessor contains, it should first be know that the making of the MC68020 has been
the product of 60 man-years of designing including the manufac- turing of the
High-density Complementary Metal Oxide Semiconductor giving the mi- croprocessor high
speed and low resistance and heat loss (Avtar, 302). Because of all the work that was put
into the MC68020 and its other related microprocessors, it is an extremely complex
microprocessor. The MC68020 operates in two modes, these are the user mode(for
application programs) or the supervisor mode (the operating system and other special
functions) (Mitchell, 155). The user and supervisor modes all have there own specific
registers to operate their functions. The user programming has 17 32-bit address
registers, and an 8-bit register (Mitchell, 155). Then the supervisor pro- gramming has
three 32-bit, an 8-bit and two 3-bit registers for small miscellaneous functions
(Mitchell, 155). All of these registers within the two modes are split up into different
groups which would hold different information as usual, but this set up of registers
gives the microprocessors a 20 32-bit information storing capacity. The next family of
microprocessor is Intel's 80386 and 80486 families. The 80386 and 80486 were mostly over
all better then the other microprocessors being made by the different companies in the
industry at this time, simply because Intel is now the leading microprocessor producer in
today's market. The 80386 was a product that evolved from Intel's very first
microprocessor, the 8-bit 8080 (Mitchell, 85). Then next came the earlier mentioned
16-bit 8086. The reason why Intel did so well in the market for microprocessors was
because every microprocessor that they made was compatible with the previous and future
(Mitchell, 85). This means that if a piece of software worked on the 8080 then it worked
on the future microprocessors and vice-a- versa. Not only did Intel look forward but they
looked back. The main difference between the 80386 and the other 32-bit microprocessors
is the added feature of a bar- rel shifter (Mitchell, 88). The barrel shifter allowed
information to switch places mul- tiple times in the registers within a single cycle
(Mitchell, 88). The microprocessor contains 8 general purpose 32-bit registers, but with
the barrel shifter that is increased to the equivalent of a 64-bit microprocessor. For
the most common 20MHz 80386 microprocessor the run time for each cycle is 59 nanoseconds,
but for a 33MHz mi- croprocessor the cycle time is reduced to 49 nanoseconds. The next
32-bit microprocessor in market are AT&T's WE32100 and 32200 (Mitchell, 5). These
microprocessors also needed six peripheral chips in order to run, these are termed:
Memory Management Units, floating point arithmetic, Maths Accel- eration Units, Direct
Memory Access Control, and Dynamic Rand Access Memory Control (Mitchell, 5). These
microprocessors apart from the microprocessors all work an important part of processing
the data that comes through the microprocessor. The difference from this microprocessor
and the others is because the WE32200 address information over the 32-bit range with the
help of a disk to work as a slow form of memory (Mitchell, 9). The WE32200 microprocessor
runs at a frequency of 24MHz (Mitchell, 9). The 16-bit and 32-bit microprocessors are a
mere page in the great book of processor history. There will be many new and extremely
different processors in the near future. A tremendous amount of time and money have been
put into the making and improving of the microprocessor. The improving and investment of
billions of dollars are continually going toward the cause of elaborating the
microprocessors. The evolution of the microprocessor will continue to evolve for the
better until the time when a much faster and more efficient electronic device is
invented. This is turn will create a whole new and powerful generation of computers.
Hopefully this paper has given the reader some insight into the world of microprocessor
and how much work has been put into the manufacturing of the microprocessor over the
years. The Evolution of The Microprocessor November 25, 1996 Bibliography Mitchel, H.J.
32-bit Microprocessors. Boston: CRC Press. 1986,1991 Titus, Christopher A. 16-Bit
Microprocessors. Indiana: Howard W. Sams & Co., Inc. 1981 Aumiaux, M. Microprocessor
Systems. New York: John Wiley & Sons. 1982 Givone, Donald D.; Rosser, Robert P.
Microprocessors/Microcomputers. New York: McGraw-Hill Book Company. 1980 Avtar, Singh.
16-Bit and 32-Bit Microprocessors: Architecture, Software, and Interfacing Techniques:
New Jersey. Englewood Cliffs. 1991