Illustrate simple ALU organisation, Computer Engineering

Q. Illustrate Simple ALU Organisation?

An ALU comprises circuits which perform data processing micro-operations. Though how are these ALU circuits used in conjunction of other registers and CU? The simplest organisation in this respect for fixed point ALU was proposed by John von Neumann in his IAS computer design.

2140_Illustrate Simple ALU Organisation.png

Figure: Structure of a Fixed point Arithmetic logic unit

The above structure has 3 registers AC, MQ and DR for data storage. Let's presume that they are equal to one word each. Please consider that Parallel adders and other logic circuits (these are the arithmetic, logic circuits) have two inputs and just one output in this figure. It suggests that any ALU operation at most can have two input values and will produce single output along with other status bits. In the current case the two inputs are AC and DR registers whereas output is AC register. AC and MQ registers are usually used as a single AC.MQ register. This register is capable of right or left shift operations. A number of the micro-operations which can be defined on this ALU are:

Addition            :  AC ← AC + DR

Subtraction        :  AC ← AC - DR 

AND                 :  AC ← AC ^ DR

OR                  :  AC ← AC   DR

Exclusive OR    :  AC ← AC (+) DR

NOT                 :  AC ← AC

In this ALU organisation division and multiplication were implemented employing shift-add/subtract operations. MQ (Multiplier-Quotient register) is a special register used for implementation of division andmultiplication. We aren't providing details of how this register can be used for implementing division and multiplication algorithms. For more details on these algorithms please refer to further readings. An example of this type of algorithm is Booth's algorithm and you should refer to it in further readings.  

For division or multiplication operations DR register stores the divisor or multiplicand respectively. The result of division or multiplication on applying certain algorithm can finally be attained in AC.MQ register combination. These operations can be signified as:

Multiplication   :  AC.MQ ← DR × MQ

Division           :  AC.MQ ← MQ ÷ DR

DR is another significant register which is used for storing second operand. Actually it acts as a buffer register that stores the data brought from memory for an instruction. In machines where we have general purpose registers any of the registers can be utilized like AC, MQ and DR.

Posted Date: 7/27/2013 3:15:12 AM | Location : United States







Related Discussions:- Illustrate simple ALU organisation, Assignment Help, Ask Question on Illustrate simple ALU organisation, Get Answer, Expert's Help, Illustrate simple ALU organisation Discussions

Write discussion on Illustrate simple ALU organisation
Your posts are moderated
Related Questions
Q. Changing the System Prompt? When you change the directory, you would like to keep track of it. The best way to do this is by displaying the name of the current directory alo

Give difference between compiler and interpreter. Compiler: It is a translator for machine independent HLL as FORTRAN and COBOL etc. Interpreter: It analysis the source

Determine the benefits of developing prototype According to SOMM [96] benefits of developing prototype are as following:  1.  Communication gap between clients and software

Hi, It is a data mining project I have a CSV file that has numbers data set. The data set contains images of handwritten digits. Recognizing handwritten digits is already a mature

Determine about the Locator Devices Mouse  A mouse is small hand-held box used to position the screen cursor. Wheels or rollers on the bottom of the mouse can be used to r

How can you manipulate the presentation and attributes of interactive lists? ---Scrolling by Interactive Lists. ---Setting the Cursor from within the Program. ---Changing

Of the two "next screen "attributes the attributes that has more priority is?? Dynamic.

Common problem with Hill climbing: An alternative way of justifying the problem is that the states are boards with 8 queens already on them, so an action is a movement of one

a. Determine any three restrictions that apply to class members. b. Is it possible for single class to be a friend of another class? Illustrate this using a suitable C++ program

In primary storage device the storage capacity is fixed. It has a volatile memory. In secondary storage device the storage capacity is not limited. It is a nonvolatile memory. Prim