ALU is the acronym for arithmetic and logic unit. This circuit performs arithmetic and logic operations in a processor.

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Function table for 32 bit ALU?

I'm trying to figure out where to start in creating a table of functions of an ALU. Specifically I'm told to assume that I have a bank of 32 of these: Then I am supposed to make a table showing all ...
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How to shift left/right a STD_LOGIC_VECTOR value within a WHEN statement?

I'm attempting to create a parametrizable ALU which handles N-Bit signed data. However the methods I know of shifting left/right, either won't work because the values are defined as STD_LOGIC_VECTOR: ...
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58 views

CISC, microcode execution flow

Say we have 16 bit processor and such CISC instruction: 0001 0010 0100 1000 As far as I understood from the answer on related question In the process of decoding, this CISC instruction will be ...
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Active high and active low in IC

I am using an alu SN74ls181 . I am unable to figure out how active high and active low are decided . Is it during the manufacturing or some circuit parameters decide if the circuit is active high or ...
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Creating an ALU slice with 8 operations

Hey, I'm trying to implement a 4bit ALU based on this 8bit alu design. The ALU has 8 different operations, given by an input of X Y Z The 8 operations are (edit: the last one is just A not, made ...
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Are there gate-level ways to produce the min or max of two binary values?

Some basics of digital logic are the half adder and full adder. We know how to produce the sum of two binary values at the level of and/or/not gates, in a straightforward way presented in many ...
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Design ALU with 2 Select lines, 2 Inputs ( n bits )

I want to design ALU with 2 select lines , 2 inputs ( n bits ) that do the following: this is a homework and I want to know what to do, writ to me the steps for design it. the first thing I thought ...
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Trouble on understanding ALU 2-bit design

I'm new to this site and I'm pretty "noobish" to electrical engineering coming from a software engineering background I was hoping someone could help me understand this design a bit. I've highlighted ...
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Is the registry file made from SRAM?

I study computer engineering and I read Hennessy's book about Computer Organization where it's described how the microprocessor does pipelining and that the microproceossor has on-chip cache, as much ...
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88 views

What's the difference between delayed branch and branch prediction?

I'm studying how delayed branch works and I'm trying to distinguish delayed branch from branch prediction. What is the difference? Is delayed branch a means to facilitate a control hazard?
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What to change when migrating designs from Altera DE2 to DE2-115?

I'm migrating a working design from Altera DE2 to Altera DE2-115 and I'm running into problems. First everything works with DE2 just like mentioned in the exercises doing what is instructed. Now I ...
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Getting my head around ALUs

What is a good place to start understanding about ALU's? Lots of sites seem very over the top and complex, can anyone recommend a good place to start? Thanks in advance, James
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4 Bit ALU addition

What are the values of the Z, V, C and N bits in the status register after the operation 1000 + 1111 for a 4-bit ALU?
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Parallel multiplication hardware

This picture is taken from Computer Organization and Design, Fourth Edition, David A. Patterson, John L. Hennessy. Sorry for the low resolution. I cannot get my head around it. I can see why the ...
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159 views

Why is carry on for an adder that is simply on? [closed]

I've understood that the behaviour is correct when I make a simple adder: But why does carry on light up just because I switch on the + operation for my 4-bit system? ...
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Running the linux kernel and ubuntu on a custom processor [closed]

This is hardly a theoretical question as many have done this, albeit there's very little information on the underlying processes. I'm developing a custom MIPS-based processor on which I would like ...
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Confused as to how implement ALU using structured VHDL

I am new to VHDL, working on assignment for my Computer architecture class: implement 32 bit ALU using VHDL, that performs only certain operations: and, ...
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779 views

Designing a simple ALU

I need to design an ALU with two 8-bit inputs A and B and control inputs x, y, and z that supports the following operations: ...
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163 views

Pipeline and real parallelism?

I have read several articles which say that the CPU has the ALU (and other small specific execution units), Control Unit and the Registers and well other buffers/pipelines, internal buses etc. The ...
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Are 32-bit ALUs really just 32 1-bit ALUs in parallell?

I'm reading the high esteemed text Computer Organization where this picture is found that is supposed to represent a 32-bit ALU: Is this technology really how it's done, just a lot of 1-bit ALUs, so ...
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Why is my carry-in activated by operation1?

I made schematics for a 4-bit ALU which performed perfectly in simulation but when downloaded to the Altera DE2 board the operation1 switch also enables carry-in for the first of the four 1 bit ALUs. ...
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CU or ALU? What communicates with memory?

I have different books saying different things. Are the address bus and data bus connected to the CU or the ALU? The control bus connects to the CU right?
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2k views

What's wrong with this 4-bit ALU?

I've put together a 4-bit ALU that seemed to perform correct in simulation but when downloaded to the board it is not behaving correctly. The operation OR behaves correctly while addition and AND are ...
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193 views

Custom-CPU builder/simulator

I googled deeply but couldn't find any cpu constructor simulator. I'm specifically hoping to learn about the operation of the northbridge, but When I googled "bridge simulator" or "bridge (the ...
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325 views

How to design system for n bits?

Say I want to design an n-bit system e.g. 256 bits. Can I generalize a 4-bit ALU which I think I know to 256 bits? These are my diagrams.
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5answers
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Is an ALU a multiplexer?

I'm studying digital electronics where the components ALU and multiplexer appear. To me the ALU seems like a multiplexer but it's not specifically mentioned that this is the case. Is it so, or why ...
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How does a chip interpret different opcodes?

I have learnt in school about opcodes and how it works with the ALU to add numbers and such, now is my question how the computer is able to understand this, because it is codes and the computer needs ...
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Need help figuring out simple multiplication hardware

As a part of my Computer Organization course, I need write to write a simple program (in C) that mics the work of "refined multiplication hardware" just like one shown in "Computer Organization and ...
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396 views

sign extend for addition and subtraction problems

I have this project for Computer Architecture, I already got to the point where I draw a 1-bit ALU for add and subs 2'C numbers. Suppose if I want to add an overflow output, how do I add to this 1-bit ...
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How are various functions (eg. add, subtract, and, etc) implemented in ALU?

I am wondering since there are so many functions an ALU need to do, how might I start implementing one (a homework where I am supposed to implement a MIPS system with Logisim, using basic Gates, ...
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How does this carry look ahead block work?

This is a carry look ahead adder : This adder is known to calculate one or more carry bits before the sum. From the figure we see that carry look ahead block calculates the carry C1,C2,C3,C4 . But ...
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How are most ALUs built, and is it possible to 'build your own'?

I've been REALLY really trying to learn about the very low level of computers. I've been looking at a lot of homebrew pages and it's quite a lot to take in. I took classes in electronic engineering in ...
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5answers
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Designing a 4-bit ALU to compute various functions

I've been working on designing an ALU that calculates various functions but I don't really know how to separate each function from one another. The inputs are 4-bit numbers A and B. I have a decoder ...
4
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574 views

Help with a simple two bit Arithmatic Logic Unit?

I'm creating a 2-bit alu. It has 8 defined functions (the functions are defined by a 3bit code), AND XOR etc, and these functions act on two, 2-bit binary numbers and produce a 2-bit answer. From ...
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299 views

Looking for a open-source ALU

I am looking for a open ALU to compute several equations like these: y1 = e^((constant1 - x)^2/(2*x)) y2 = constant2/y1 y3 = y2*constant3 + x*constant4 Where x ...
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How to find out if a binary number is zero

I was implementing the ALU from the specs given in my The Elements of Computing systems book. I am stuck on only one problem. How do I find if a given number is zero or not. One thing I can do is or ...