Simple-As-Possible 1 Architecture

This architecture has an 8-bit memory. It consist of 4-bit PC (Program Counter) which is part of Control Unit that counts from 0000 to 1111 in binary form and its job is to send the address to the memory. 8-bit IR (Instruction Register) is also a part of the Control Unit which contents of the instruction register that are split into two nibbles; the upper and lower nibbles. SAP 1 has a RAM (Random Access Memory) that allows to store data in memory before a computer or a program runs. SAP 1 can only perform two logical operation; addition and subtraction. Its uses 2's complement, 8-bit adder-subtracter unit. SAP 1 architecture has a controller/sequencer that controls the operation of the computer. Every computer operates in what we call instruction cycle, or fetch/execute cycle: Fetch get an instruction from the memory and Execute perform the instruction. SAP 1 architecture has only five instruction set; LDA (Load Accumulator), ADD (Addition), SUB (Subtraction), OUT (Output) and HLT (Halt). ADD instruction will add the contents of the Accumulator to the contents of memory in the address, placing the sum back into the Accumulator.

In relation with the early microcomputer design they are the same 8-bit of memory and 8-bit bus for data and address transfer.

Commodore 64

The Commodore 64 was one of the most popular of its era and it is the best-selling model of home computer of all time.

The C64 uses an 8 bit MOS Technology 6510 microprocessor. This is a close derivative of the 6502, with an added 6-bit internal I/O port that in the C64 is used for two purposes: to bank-switch the machine's ROM in and out of the processor's address space, and to operate the datasette tape recorder. The C64 has 64 KB of RAM, of which 38 kB are available to built-in Commodore BASIC 2.0.

source: wikipedia.com

The Early Microcomputer Design

Microcomputer

A computing device made up of one or more microprocessors, random access memory (RAM), input/output logic, and usually one or more data input and data output devices. Desktop computers (personal computers) are all also called microcomputers.

A microcomputer is a personal computer. It's considered a personal computer because people can use it in their homes. Microcomputers were invented in the 1970s. Before the invention of microcomputers, people used mainframes and minicomputers. They were big, bulky, expensive computers used at companies and universities. Microcomputers were smaller and cheaper than mainframes and minicomputers.

Microcomputers use a microprocessor, which is an integrated circuit that's referred to as the central processing unit. The microprocessor is able to move information back and forth through its transistors.

Intel and Motorola took center stage in the development of microprocessors in the 1970s, although Zylog and Texas Instruments made microprocessors. Intel's first microchip, the MCS4 or 4004, had four 16-pin chips with 2,300 transistors and 45 instructions and could handle a word length of up to 4 bits.

Intel's 8008 microchip made it possible for one microprocessor to perform multiple tasks. Intel 8008 microprocessors had 3,500 transistors, 66 instructions and 8-bit register, meaning it could hold up to eight word lengths of information.

Mark-8 was one of the first microcomputers to use the Intel 8008 microchip, in 1974. The computer came in parts and was sold as a kit. When Intel developed the Intel 8800 microchip, it was used in 1975 with the Altair 8800 computer kit. Bill Gates and Paul Allen developed the Basic Interpreter for the Altair 8800. IBM used Intel 8088 to design its first microcomputer and called it a personal computer. In 1980, Gates and Allen supplied IBM with the DOS operating system software to be used with their computer model.

source: businessdictionary.com, ehow.com

The Early Microcomputer Design

A collection of early microcomputers, including a Processor Technology SOL-20 (top shelf, right), an MITS Altair 8800 (second shelf, left), a TV Typewriter (third shelf, center), and an Apple I in the case at far right.

The MITS Altair 8800 is a microcomputer design from 1975 based on the Intel 8080 CPU. The Altair bus consists of the pins of the Intel 8080 run out onto the backplane. Another oddity was that the system included two unidirectional 8-bit data bus, but only a single bidirectional 16-bit address bus.

source: wikipedia.com