How are math instructions implemented on hardware?

Question

I'm looking for some sample code that "emulates" the most frequently used math instructions(addition,subtraction,multiplication,division) and will cover all steps that a hardware based cpu processor follows.

The first thing i did was to use google and got this : https://bochs.svn.sourceforge.net/svnroot/bochs/trunk/bochs/cpu/

But its not what i want.This is an instruction wrapper/emulator while i want to see how the cpu does everything down to bit level...

..

read about NAND gates and how they are used to implement these basic instructions — Prinzhorn, Jul 29 '12 at 21:06
compile some example code and let the compiler output a mixed c/asm list file. Then, inspect the result :) — huysentruitw, Jul 29 '12 at 21:06
The problem is that i want to see what the actual instruction does behind the scenes... — user1010005, Jul 29 '12 at 21:18

score 2 · Answer 1 · answered Jul 29 '12 at 21:05

2

TTL is a great way to get introduced to digital logic. If you search Google for something like "TTL arithmetic", you'll probably get lots of links to tutorials about how to create things like adders and multipliers.

(Of course knowing what to search for is half the problem.)

answered Jul 29 '12 at 21:05

Greg Hewgill

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I have a test board that i still haven't even unpacked :o so i would like to see some software implementation first – user1010005 Jul 29 '12 at 21:19
It's actually a lot easier to do this sort of thing in hardware than it is to "simulate" it in software. – Greg Hewgill Jul 29 '12 at 22:08

score 1 · Answer 2 · answered Jul 29 '12 at 21:22

1

You should Google for two's complement arithmetic.

This Computer Arithmetic Algorithms Simulator may interest you.

answered Jul 29 '12 at 21:22

Borodin

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score 1 · Answer 3 · edited May 23 '17 at 12:13

If you really want 'code that "emulates",' (in its literal terms) you'll need a parser for Boolean Algebra grammar:

S ::= E;
E ::= (E)
E ::= T AND T
E ::= T OR T
E ::= T NOR T
T ::= NOT T
T ::= IDENTIFIER # Set of named bits
...
Include grammar for STATEMENTs.

Simply, write a parser for the above grammar so that you can start writing code in Boolean Algebra.

# Half Adder
SUM = A NOR B;
CARRY = A AND B;

Edit: I realize that this SO question already defines a solution. Boolean expression (grammar) parser in c++

From here, you can build an Arithmetic Logic Unit (ALU) in the von Neumann Architecture that should be able to handle of the aforementioned arithmetic: http://en.wikibooks.org/wiki/Microprocessor_Design/ALU

score 1 · Answer 4 · answered Jul 29 '12 at 21:27

1

The Wikipedia article on the arithmetic logic unit (ALU) has a number of links which might be useful to you. Among them articles about addition, multiplication and division.

answered Jul 29 '12 at 21:27

MvG

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How are math instructions implemented on hardware?

4 Answers4