The Microprocessor

The Microprocessor 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.

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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 …