Tutorials/Redstone computers

=Preface= This article covers the design and implementation of functional computational systems, therefor by nature it is only meant for the most advanced Redstone engineers.

=Planning= When designing a computer ( Redstone or otherwise ) key design decisions will affect the organization, size and performance of your prospective computer and should be made concretely prior to construction.

For each of the following fields of design consideration; having a decided upon selection will provide guidance during the planning and construction of various sub-systems and components.


 * Execution model ( The computers organization of memory relating to program storage and execution )
 * Word-size ( The size of information blocks which the computer will operate on )
 * Instruction Set ( The set of operations which a computer will execute )

Execution model
The technique of storing blocks of instructions called programs within memory is what allows computers to perform varying tasks.

The apparatus employed by a computer for storing and retrieving these programs is the computers Execution model.

Two of the worlds most successful Execution models Harvard and von Neumann run on nearly 100% of the the computers available today.

Harvard
The Harvard architecture physically separates the apparatus for retrieving the instructions which makeup an active program from that of the data access apparatus which the program accesses during execution.

Programs written for computers employing a Harvard architecture may perform upto %100 faster for tasks which access the main memory bus, note however certain memory circuitry is necessarily larger for those who select a Harvard architecture.

von Neumann
The von Neumann architecture uses a two-step process to execute instructions, first memory containing the next instruction is loaded, then the new instruction just loaded is allowed to access this same memory as it executes, using a single memory for both program and data facilitates Meta-Programming technology like compilers and Self modifying Code.

The von Neumann architecture was the first proposed model of computation and almost all real-world computers are von Neumann in nature.

Word sizes
Word-size is a primary factor in a computers physical size.

Common real-world Word-sizes were once quite fragmented, until the advent of the IBM System/360 which brought with it the now familiar 8-bit Byte and forever standardized machine words-sizes as multiples of 8.

In Minecraft; machines from 1-bit all the way to 32-bit have been successfully constructed.

The most common word-size combinations are:

Data-Word
The amount of data a computer can manipulate at any particular time is a representation of it's Data Word-size.

The Data-Word is also exactly the width of the computers main bus, among other things; it governs the maximum size of numbers which can be processed by the ALU.

Instruction-Word
The amount of data a computer needs to complete one single instruction is a representation of it's Instruction Word-size.

To minimize memory misalignment while retrieving instructions to be executed, most computers use an Instruction-Word size which is a multiple of it's Data-word size;

=Design=