Cambridge Z88
Encyclopedia
The Cambridge Computer Z88 is an A4-size, lightweight, portable
Portable computer
A portable computer is a computer that is designed to be moved from one place to another and includes a display and keyboard. Portable computers, by their nature, are generally microcomputers. Portable computers, because of their size, are also commonly known as 'Lunchbox' or 'Luggable' computers...

 Z80
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...

-based computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...

 with a built-in combined word processing
Word processing
Word processing is the creation of documents using a word processor. It can also refer to advanced shorthand techniques, sometimes used in specialized contexts with a specially modified typewriter.-External links:...

/spreadsheet
Spreadsheet
A spreadsheet is a computer application that simulates a paper accounting worksheet. It displays multiple cells usually in a two-dimensional matrix or grid consisting of rows and columns. Each cell contains alphanumeric text, numeric values or formulas...

/database
Database
A database is an organized collection of data for one or more purposes, usually in digital form. The data are typically organized to model relevant aspects of reality , in a way that supports processes requiring this information...

 application called PipeDream, along with several other applications
Application software
Application software, also known as an application or an "app", is computer software designed to help the user to perform specific tasks. Examples include enterprise software, accounting software, office suites, graphics software and media players. Many application programs deal principally with...

 and utilities, such as a Z80-version of the BBC BASIC
BBC BASIC
BBC BASIC is a programming language, developed in 1981 as a native programming language for the MOS Technology 6502 based Acorn BBC Micro home/personal computer, mainly by Sophie Wilson. It is a version of the BASIC programming language adapted for a U.K...

 programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....

.

The Z88 evolved from Sir Clive Sinclair
Clive Sinclair
Sir Clive Marles Sinclair is a British entrepreneur and inventor, most commonly known for his work in consumer electronics in the late 1970s and early 1980s....

's Pandora portable computer project which had been under development at Sinclair Research during the mid-1980s. The machine was launched at the Which Computer? Show on February 17, 1987.

Technical description

The Z88 is a portable computer weighing 0.9 kg, based on a low-power CMOS
CMOS
Complementary metal–oxide–semiconductor is a technology for constructing integrated circuits. CMOS technology is used in microprocessors, microcontrollers, static RAM, and other digital logic circuits...

 version of the popular Zilog Z80
Zilog Z80
The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...

 microprocessor
Microprocessor
A microprocessor incorporates the functions of a computer's central processing unit on a single integrated circuit, or at most a few integrated circuits. It is a multipurpose, programmable device that accepts digital data as input, processes it according to instructions stored in its memory, and...

. It comes with 32 KiB of internal pseudo-static RAM and 128 KiB of ROM
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

 containing the operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...

 (called OZ). The memory can be expanded up to 3.5 MiB
MIB
MIB may refer to any of several concepts:* Master of International Business, a postgraduate business degree* Melayu Islam Beraja, the adopted national philosophy of Brunei* Motion induced blindness, a visual illusion in peripheral vision...

 of RAM, the contents of which are preserved across sessions. An integrated capacitor prevents the Z88 from losing its data for the limited amount of time it takes to change the batteries.

The machine uses a membrane keyboard
Membrane keyboard
A membrane keyboard is a computer keyboard whose "keys" are not separate, moving parts, as with the majority of other keyboards, but rather are pressure pads that have only outlines and symbols printed on a flat, flexible surface...

, which is almost silent in use; an optional electronic "click" can be turned on to indicate keystrokes. The Z88 is powered by four AA batteries, giving up to 20 hours of use. It has three memory card slots, which accommodate proprietary RAM, ROM or EPROM
EPROM
An EPROM , or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off. In other words, it is non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages...

 cards, the third slot being equipped with a built-in EPROM programmer. Card capacities range from 32 KiB to 1 MiB.

The Z88 has a built-in eight-line, "super-twisted
Super-twisted nematic display
A super-twisted nematic display is a type of monochrome passive matrix liquid crystal display . STN displays provide more contrast than twisted nematic displays by twisting the molecules from 180 to 270 degrees...

" LCD
Liquid crystal display
A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

 display, which has greater contrast than conventional twisted nematic LCDs.

Memory map

The 64 KiB addressable by the Z80 processor are divided in four banks of 16 KiB each. The maximum memory of 4 MiB for the system is also divided in 256 segments of 16 KiB each. The hardware can map any of the 16 KiB blocks to any of the four banks. The first 512 KiB are reserved for ROM; the next 512 KiB are reserved for internal RAM. The next 3 MiB are assigned to each one of the three memory slots.

Current status

The Z88 had something of a cult following, and is still used by a few enthusiasts. A variety of software is available including games and utilities. Since 1998, a 1 MiB Flash memory
Flash memory
Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...

 card is available which provides convenient non-volatile
Non-volatile memory
Non-volatile memory, nonvolatile memory, NVM or non-volatile storage, in the most basic sense, is computer memory that can retain the stored information even when not powered. Examples of non-volatile memory include read-only memory, flash memory, ferroelectric RAM, most types of magnetic computer...

 storage. Once written to the card, files are safe and not reliant on a power supply. Unlike traditional EPROM cards (erased with an external ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

 light), this one can be electrically erased in the computer's slot. The first generation of card only worked in slot 3 where a 12V signal (Vpp) is available. The later generation is based on AMD
Advanced Micro Devices
Advanced Micro Devices, Inc. or AMD is an American multinational semiconductor company based in Sunnyvale, California, that develops computer processors and related technologies for commercial and consumer markets...

chips and runs with 5V for erasure. It is possible to read, write and erase flash cards in the three slots and the internal one.

It is also possible for an experienced user to replace the built-in 32 KiB RAM chip with a bigger 128 or 512 KiB static RAM chip. However, the latter requires some extra board modifications, and 512 KiB is the biggest size that can be addressed by the Z88 for the internal RAM. A similar modification is possible for the internal EPROM slot. A 512 KiB flash chip can replace the original ROM, allowing an upgrade of the operating system.

External links

The source of this article is wikipedia, the free encyclopedia.  The text of this article is licensed under the GFDL.
 
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