Processor Type

Processor Type

1. RISC (Reduced Instruction Set Computer)

    - CPU Apple

2. CISC (Complex Instruction Set Computer)

    - AMD and Intel CPU

RISC stands for Reduced Instruction Set Computer. Is part of the microprocessor architecture, small form and function to negeset istruksi in communication between the other architectures.

History of RISC

The first RISC projects created by IBM, Stanford and UC-Berkeley in the late 70th and early '80s. IBM 801, Stanford MIPS, and Berkeley RISC 1 and 2 are made with the same concept that is known as RISC. RISC has the following characteristics:

• one cycle execution time: one round of execution. RISC processors have a CPI (clock per instruction)

   or the time per instruction for each round. It is intended to optimize each instruction on

   The CPU.

• pipelining: is a technique that allows to perform execution simultan.Sehingga

   process more instructions efiisien

• large number of registers: The number of registers that very much. RISC in the design is intended to be

  accommodate the number of registers is very much to anticipate in order to avoid interaction

  excess with memory.

Shortened by CISC. The series of built-in instructions to the processor which consists of complex commands. These instructions are available makes it easier for programmers to develop applications for CISC plattform. On the other hand, the number of instructions in a CISC to reduce speed. Intel's x86 chips are CISC chip of this type because it uses a complex set of instructions.

CISC is the opposite of RISC, is usually used in the processor family for the PC (AMD, Cyrix). Intel competitors such as Cyrix and AMD have also been using RISC chips but it has been equipped with the exchanger (converter) CISC.

Here will membahagikan chip RISC type of operation to some operations are more easily so that there are small orders that are able to process quickly.

The microprocessor designers seeking better performance within the limitations of contemporary technology. In the 1970's for example, memory is measured in kilobytes and very expensive at that time. CISC is the dominant approach because it saves memory.

On CISC architectures like the Intel x86, which was introduced in 1978, there could be hundreds of program instructions - simple commands that tell the system to add numbers, store the value and displays the results. When all the instructions the same length, simple instructions will waste memory. Simple instruction requires 8 bits of storage space, while the most complex instruction consumes a total of 120 bits.

Although with varying length instructions processed by the chip harder, longer CISC instruction will be more complex. However, to maintain software compatibility, x86 chips such as Intel Pentium III and AMD Athlon should work with CISC instructions that are designed in the 1980s, despite the initial advantage of memory saving is not important now.

Advantages and disadvantages of the two architectures are often the perdebatatan among experts. However, new technology using this RISC architecture.

RISC with CISC difference in terms of instructions

RISC (Reduced Instruction Set Computer)

- Emphasis on software, with a few transistors

- Simple instructions and even single

- Load / Store or memory into separate working memory

- The size of the code and kecapatan higher

- Transistor in it more for the memory register

CISC (Complex Instruction Set Computer)

- More emphasis on hardware, according to his destiny to pragramer.

- It has a complex instruction. Load / Store or Memory to Memory in cooperation

- Having a small code size and low speed.

- The transistor in it is used to store instructions - instructions are complex

We have often heard a pretty interesting debate between IBM-compatible personal computer that is labeled with the Intel Inside are labeled Apple PowerPC computers. The main difference between the two computers that have the type of processor it uses. PowerPC processors from Motorola is a major brain trust Apple Macintosh computer as RISC processors, while Intel's Pentium processor is believed to CISC. The fact that personal computers based on Intel Pentium personal computer today is the most populated. But it also can not deny that the RISC-based computers such as Macintosh, SUN is a reliable computer system with pipelining, superscalar, floating point operations and so forth.

Is it better than RISC over CISC or vice versa. But we know where exactly lies the difference. Is the processor with instructions that fewer would be better than the processor complex and complete instructions. Is it different from many processors it is just whether or not the instruction only. Is not the number of instructions not related to an a-reliable-processor. These questions are being answered through the following article. But so much closer to practical electronics, ElectronicLab will focus more on low-cost microcontroller-based RISC and CISC. As an example of a CISC microcontroller is 68HC11 made by Motorola and Intel 80C51. We also know the family PIC12/16CXX from Microchip and National Semiconductor COP8 made a RISC-based microcontroller.

CISC stands for Complex Intruction Set Computer processor which has a complex set of instructions and complete. While RISC stands for Reduced Instruction Set Computer, which means the processor has a set of instructions that program a little more. Because there are differences both in word or a complex set of simple instructions (reduced), then let's discuss a little about the instruction itself.

Microcontroller system always consists of hardware (hardware) and software (software). This software is a sequence of commands or instructions that are executed by a processor in a sequential way. Instruction itself is actually bits of logic 1 or 0 (binary) in program memory. These binary numbers if the width is 8 bits called a byte and if 16 bits called a word. Rows of this binary logic that is read by the processor as a command or instruction. To be more concise, it is a binary number usually represented by the hex number (HEX). But for people, write a program with binary or hex numbers really troublesome. So they invented the assembler language represented by the cutting down of words is quite understandable by humans.

Assembler language is usually taken from the English and the presentation is called the Mnemonic. Each plant with a homemade chip microprocessor complete set of instructions that will be used to make the program.

Binary Hexa Mnemonic

10110110 B6 LDAA ...

10010111 97 staa ...

01001010 4A DECA ...

8A ORAA 10001010 ...

00100110 26 bne ...

00000001 01 NOP ...

7E 01111110 JMP ...

Most of 68HC11 instruction set

At first, the instructions are very simple and small. Then the microprocessor designers vying for the complete set of instructions is as complete as possible. The number of instructions that evolve with the development of a more complete microprocessor design with the addressing mode is mixed. Microprocessor and has a lot of bit manipulation instructions and so on are equipped with arithmetic instructions such as addition, subtraction, multiplication and division. As an example 68HC11 has a lot of sets of instructions for branching as bne, BLO, BLS, BMI, BRCLR, BRSET and so on.

The designer also broaden the variety of microprocessor instructions to create a single instruction for the program is usually run with a few instructions. For example, the 80C51 for example the following program.

LABEL ...

...

DEC R0

MOV A, R0

JNZ LABEL

Program 'decrement' 80C51

This program is a program that reduces the repetition of the contents of register R0 to register R0 into an empty (zero). Intel adds instructions to create a set of special instructions for this:

LABEL ....

DJNZ R0, LABEL

Instruction 'jump not zero decrement' 80C51

The second example of this program is no different result. However, complex instructions such as program makers DJNZ easier. Complete set of instructions that will hopefully make the user more flexibility microprocessor assembler language to write programs in a high level programming language approach. Intel 80C51 processor base developed from 8048 was released in 1976 has no less than 111 instructions. No lag, the popular 68HC11 from Motorola in 1984 equipped with 145 instructions. Due to numerous and complex instructions that 68HC11 and 80C51, two examples of this microcontroller is referred to as CISC processors.

RISC versus CISC debate began in 1974 when IBM developed the RISC processor 801. The argument used is why it takes time complex instructions. Because, in principle, a complex instruction can be done by the instructions simpler and smaller. When the use of high-level languages ​​such as Fortran and other compilers (compiler / interpreter) begins to develop. Moreover, the current compiler such as C / C + + are commonly used. So it is not really necessary instructions in the processor complex. Compiler that will work to translate programs from high-level language into machine language.

To see how the difference in RISC and CISC instruction, let's see how they do the multiplication for example c = ax b. 68HC11 microcontroller to do with the program as follows:

LDAA # $ 5

LDAB # $ 10

Mul

Program 5 × 10 with the 68HC11

Just three lines only and after this the 68HC11 D accumulator will contain the results of the multiplication of accumulator A and B, ie, 5 x 10 = 50. The same program with PIC16CXX, is as follows.

Movlw 0 × 10

Movwf REG1

Movlw 0 × 05

Movwf Reg2

CLRW

LOOP addwf REG1, 0

CFSZ Reg2, 1

GOTO LOOP

...

...

Program 5 × 10 with PIC16CXX

A RISC processor PIC16CXX this, do not have a specific product instructions. But the multiplication 5 × 10 is the same as the sum of the value 10 5 times. It seems to make an assembly program with RISC processors become more complex as compared to CISC processors. But keep in mind, to make complex instructions like MUL instruction and other instructions elaborate on CISC processors, complex hardware is required as well. It takes thousands of logic gates (logic gates) transistors to make such a processor. Complex instruction also requires a number of machine cycles (machine cycle) longer to be able to complete execution. Multiply instruction MUL on the 68HC11 require 10 machine cycles and instruction division requires 41 machine cycles.

RISC proponents conclude, that the processor will not elaborate more quickly and reliably. Almost all RISC processor instructions are basic instructions (not necessarily simple), so these instructions are generally only require one machine cycle to run. Except for branching instructions that require two machine cycles. RISC is usually made with a Harvard architecture, because architecture that allows it to make the execution of instructions completed in one or two machine cycles.

By comparison the number of instructions on RISC processors, COP8 only equipped with 58 instructions and PIC12/16CXX only has 33 instructions only. To realize the basic instructions that this amount is not much, RISC microprocessors do not require a lot of logic gates. Because the dimensions of the IC dice and RISC processor power consumption is generally lower than CISC processors. Not by coincidence, many PICXX microcontroller family that was released to the market with mini size. For example, the microcontroller PIC12C508 DIP 8 pin.

CISC and RISC difference was not significant if only viewed from the terminology of complex instruction set or not (reduced). Moreover, RISC and CISC architecture is different in philosophy. CISC architecture philosophy is to move the software into the hardware complexity. IC manufacturing technology currently allows for menamam thousands and even millions of transistors on a single dice. Various instructions are approaching a high level language programmers can be made in order to facilitate the programmers to make programs. CISC processors typically have some form of firmware microcode in the internal chip it useful to translate the macro instruction. This mechanism could slow down the execution of instructions, yet effective way to create complex instructions. For certain applications that require singlechip computer, CISC processors could be an option.

In contrast, the philosophy of RISC architecture is a processor architecture that is not complicated by limiting the number of instructions only on the basis of instructions as needed. Complexity to program in machine language addressed by making high-level programming language and compiler as appropriate. Because it is not complicated, the theory RISC microprocessor is a low-cost microprocessors in the true sense. However, excess space on a RISC processor used to create additional systems that exist in today's modern processors. Many RISC processors in the chip-equipped with superscalar systems, pipelining, memory caches, registers, and so forth, whose purpose is to make it a faster processor.