Microprocessor Architecture

A microprocessor is a device that incorporates almost all of the functions of a computer’s central processing unit (CPU) on a single integrated circuit (IC, or microchip).

The first devised microprocessors emerged in the early 1970s and were used for electronic calculators, using binary-coded decimal (BCD) arithmetic on 4-bit words. Other embedded are users of 4-bit and 8-bit microprocessors, such as terminals, printers, various kinds of automation etc., followed soon after. Presently commonly used 8-bit microprocessors with 16-bit addressing also led to the first general-purpose microcomputers from the mid-1970s on.

During the year 1960s, computer processors were often constructed out of small and medium-scale ICs containing from tens to a few hundred transistors. The integration that of a CPU onto a single chip greatly reduced the cost of processing power. From this poor beginning it continued increasing in the microprocessor capacity having rendered other forms of computers almost completely obsolete, with one or more microprocessors used in everything from the smallest embedded systems and handheld devices to the largest mainframes and supercomputers.

Classification of Microprocessor:

Classifications are mainly characteristics that determine the type of microprocessor in a broad sense.  Characteristics of the microprocessor are normally determined at the beginning of its design as a set of design guide lines.  For example, in the early times, the chip's design will be decided whether the chip will support variable length instructions or not.  This initial design choice will have a significant impact on the final design.  The processor may be classified into these types:

• CISC
• RISC
• EPIC

CISC Processors:

(Complex Instruction Set Computing)

These microprocessors have characteristics that fit most early microprocessor designs.  In some types of applications, the rate at which data can be fetched from memory is a limiting factor to the performance of the application.  

RISC Processors:

(Reduced Instruction Set Computing)

After manufacturing CISC chips for some time, they found out that some CISC design guide lines were not such a good idea.  With these ideas in mind, the RISC chip was created. 

EPIC:

(Explicitly Parallel Instruction Computing)

EPIC microprocessor is the brand new classification. One special thing about EPIC chips is that the CPU not having to check for parallelism, or in other words, check which instructions it can execute in parallel. The compilers are responsible for determining which instructions can be executed in parallel and encoding that information within the machine code.