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. How can one decide this decimal position? Decimal position can be signified by a position between flip-flops (storage cells in computer). However how can one decide this dec

Business Narrative Aussie Wine Tours (AWT) conduct tours of the wineries of Victoria's Yarra Valley wine region. The tours take place on the last Sunday of each month. Currentl

What is User Defined Functions? User-Defined Functions permit defining its own T-SQL functions that can accept 0 or more parameters and return a single scalar data value or a t

During the Persian Gulf crisis of 1991, U .S forces deployed a Dynamic Analysis and Re planning Tool, DART ( Cross and Walker, 1994) to do automated logistics planning and schedu

What are the disadvantages of Bespoke Software -  Very dependent on suppliers of the software; if they go out of business there would be little or no support if problems occ

Q. Describe Loading Disk Operating System? Different version of DOS, such as 2.0, 3.0, 3.2, 4.0, 5.0, 6.0, 6.2, 6.22, 7.0, 7.2 are present. The newer versions have additional

What is data mining? Data Mining: It is an analytic process designed to explore data and after that to validate the findings through applying the detected patterns to lat

What is a privileged instruction? To protect the operating system of a computer from being corrupted by user programs, particular instructions can be executed only whereas the

Multithreaded Architecture:  It is clear now that if we give many contexts to multiple threads, then processors with multiple contexts are known as multithreaded systems. These sys

Determine the abstraction mechanisms for modelling The object orientation conceptual structure helps in providing abstraction mechanisms for modelling, that includes: Cl