Showing posts with label home computer. Show all posts
Showing posts with label home computer. Show all posts

Wednesday, June 26, 2019

The home computer

A home computer is a micro computer, which entered the market with the birth of the Altair 8800 on 1975 and extends until the early 1990s. This encompasses almost all 8-bit computers. Commonly used CPUs were the Zilog Z80, MOS Technology 6502 or Motorola 6800 and the first wave of micros equipped with 16-bit CPUs, mainly Motorola 68000 and Intel 8086 and 8088. The term home computer describes from a computer commonly found in the industry and take it home. Excluded from this group are IBM PCs and compatibles.These are called personal computers.

Development

Commodore 64The Altair 8800 was the first home computer but lacked a keyboard and monitor. 1977 saw what the BYTE magazine called the 1977 Trinity and encompassed the Commodore PET, Tandy TRS-80 and Apple 2. They came with a built-in keyboard. The Commodore and Tandy also sported a monitor. Shortly after Atari introduced their 8-bit line of micros. In the United Kingdom computers like the Sinclair ZX 81 and Spectrum as well as the Acorn Atom, better known as BBC Micro, became famous. Many teenager began coding, mainly writing games. They became soon known as bedroom coders. All home computers but the Jupiter ACE had the BASIC programming language built in. The best selling machine was the Commodore 64.

Some types of computers stayed for longer, others evolved trying to maintain compatibility. For example was a Z80 card available for the Apple II as well as for the Commodore 64, opening the huge world of CP/M software for their owners. However, by the end of the 1980s most were eliminated by IBM compatible personal computers and the newer generations of video game consoles because all used their own incompatible formats. The IBM revolution was triggered in 1981 by the output of the IBM 5150 personal computer, the IBM PC.

I got my first micro with the Commodore 64 in 1984. I also had some BASIC knowledge but soon learned to code in 6502 (the C 64 had a 6510 though) assembly language. I soon wanted a Commodore Amiga 500 but waited until 1988 the price came down. After that I only bought IBM compatibles.

Wednesday, June 6, 2018

Zilog Z80 CPU

The Zilog Z80 is an 8-bit microprocessor designed and manufactured by Zilog. One of the peculiarities of this processor is the coupling of some 8-bit registers to a 16-bit register. This with a 16-bit address bus allows for much faster processing of data than with a conventional 8-bit processor.

This processor was marketed for the first time in July 1976. In the early 1980s it was very popular in the design of 8-bit computers such as Radio Shack TRS-80, Sinclair ZX80, ZX81, ZX Spectrum, MSX standard, Amstrad CPC, PC-88 and later in embedded systems. With the MOS 6502 family, it dominated the 8-bit micro computer market from the late 1970s to the mid-1980s and was still used in then new Amstrad computers until 1995.

The Z80 was designed to be compatible with the Intel 8080, so the majority of the code for 8080 could work without much modification on the Z80. The CP/M operating system was designed around Intel 8080 based systems and could also work without modification on Z80 based systems.Z80 based systems were generally more powerful and had more features than systems based on 8080 CPUs. Some versions of CP/M applications only existed in a Z80 version.

History and overview

Z80 CPU DIP by DamicatzThe Z80 came into being when Federico Faggin, after working on the 8080, left Intel at the end of 1974 to found Zilog together with Ralph Ungermann to put the Z80 on the market in July of 1976. It was designed to be binary compatible with the Intel 8080 so that most of the 8080 code, including the CP/M operating system, works without modification on it. The Z80 quickly took over share from the 8080 on the market, and became one of the most popular 8-bit processors. Perhaps one of the keys to Z80's success was the integrated refresh of DRAM, and other features that allowed systems to be built with fewer chips. For the first NMOS generation, the maximum clock rate increased gradually. First at 2.5 MHz, then by the well known 4 MHz (Z80a), up to 6 (Z80b) and 8 MHz (Z80h). A CMOS version was developed with frequency limits ranging from 4 MHz to 20 MHz and some versions were sold until the 2000s. The CMOS version also has a low power sleep mode, with processor state retention. The Z180 and eZ80, fully compatible derivatives, have specifications for up to  50 MHz.

Use in systems

The Z80 CPU saw uses including in Texas Instruments calculators, SEGA Master System, GameBoy, and Game Gear video game consoles. Some more powerful consoles with other central processors like the Neo Geo or the Mega Drive with its Motorola 68000, used the Z80 as an addon processor to handle sound or system I/O.