| Release date | 1985 |
|---|---|
| Operating system | EXOS BASIC |
| CPU | Zilog Z80A @ 4 MHz |
| Memory | 64KB / 128KB |
The Enterprise is a Zilog Z80 based home computer first released in 1985. There are two variants, the Enterprise 64 with 64 kB of RAM, and the Enterprise 128 with 128 kB.
Contents |
The machine has a Z80 CPU running at 4 MHz,[1] 64 kB or 128 kB of RAM, and 32 kB of internal ROM containing the EXOS operating system and a screen editor / word processor. BASIC was supplied on a 16 kB ROM module.
Memory is expandable up to 4 MB using bank switching scheme. The 64 kB address space of the Z80 processor is divided into four 16k sections. One of the 256 16k memory pages can be mapped individually into each of the sections. The top four pages (64 kB) are used as video RAM, but it is possible to store program code and data there, too. The system ROM is mapped on the lowest two pages. The next four pages were reserved for ROM cartridge (max 64 kB).
Two ASIC (aka ULA) chips take some of the workload off the central processor. They are called "Nick" and "Dave", named after their designers: Nick Toop, who had previously worked on the Acorn Atom, and Dave Woodfield. Nick handles graphics, while Dave handles sound and memory paging.
The case is unique for its time, at least in the UK, for containing both a full-sized keyboard with programmable function keys and a joystick. Its overall shape was also notably distinctive compared to the more conservative designs of the time, the designers stating that they wanted break away from the norm.[2] The keyboard is low profile and ergonomic, with standard keyboard layout, but the feel of the keys did receive some negative reviews. It is constructed with a rubber membrane, on top of which the mechanical keycaps are installed. (This is pretty much how low-cost PC keyboards are constructed these days.) The joystick which replaces the normal cursor keys allows moving cursor even in diagonal directions. The product design firm hired by Robert Madge to design and engineer the case and keyboard was Hollington Associates, a London-based consultancy. Geoff Hollington and Nick Oakley, both graduates of the Royal College of Art, were responsible for the design.
Enterprise has 5 graphics modes: 40 and 80 column text modes, Lo-Res and Hi-Res graphics (bit mapped), and attribute graphics. On top of this, 2, 4,16 or 256 colours can be selected in bit mapped graphics modes, but more colours gives lower horizontal resolution. Interlaced or non-interlaced mode can be used. The highest resolution is 640×512 pixels interlaced or 640×256 pixels non-interlaced, but this only allows 2 colours. With 256 colours, the maximum resolution is 80×256. The attribute graphics mode gives 320×256 pixel resolution with 16 colours selectable from palette of 256.
Multiple pages can be displayed on screen simultaneously, even pages with different graphics modes. Each page has its own palette, thus allowing more colours to be displayed on screen simultaneously. The height of the page can be larger than the screen or the window it is displayed on. Each page is connected to a channel of the EXOS operating system, so it is possible to write even on a hidden page.
The sound is handled by the second ASIC chip, Dave. It has 3 sound channels plus a noise channel, in stereo. The sound from each channel can be freely placed (left-right) in the stereo image. Distortion, low-pass and high-pass filters and ring modulation can be used.
In addition, the chip has programmable envelope generators that are more flexible than the traditional ADSR envelope. Up to 255 phases can be specified for each envelope. On each phase, the envelope can slide the sound pitch and left/right volume a given amount in the given time.
The machine came with a surprising array of connectors, far beyond what was common on home computers of the time. There is an RGB output, RS232 / RS423 serial port, a Centronics printer port, two external joystick ports, two cassette interfaces, a ROM cartridge slot and an ordinary expansion port. To save money, however, many of the connectors on the rear did not come with sockets but instead had simple edge connectors using the exposed traces on the edge of the printed circuit board.
The BASIC ROM can even be replaced by a ROM which can emulate a ZX Spectrum, thus in theory allowing the Enterprise to run the existing catalogue of thousands of Spectrum games. Later, an external floppy drive became available, supporting CP/M programs.
EXOS (Enterprise Expandable Operating System) on the system ROM is based on channels. All devices, such as display, keyboard, printer, tape and disk interfaces are accessed using channels. This allows the programs to treat all input and output devices in an identical fashion.[3]
In addition, the system ROM contains a full screen editor, which doubles as simple word processor. It can be used to edit BASIC programs or any other language programs or other text files. The editor takes advantage of the joystick for cursor control.
Unlike most other home computers of the time, Enterprise does not have BASIC or any other programming language in the internal ROM. Instead, the BASIC interpreter was supplied on a 16k ROM cartridge, so the language can be changed just by switching the cartridge. Acorn's BBC Micro had a similar system.
IS-Basic quite strictly follows the ANSI BASIC standard.[4] It is a fully structured language with wide set of control structures. These include multi-line IF...THEN...ELSE, SELECT...CASE, DO...LOOP with WHILE and UNTIL conditions at the begin and/or end of the loop and EXIT LOOP statement. Procedures and functions can have both reference and value parameters and local variables. Errors and other exceptions are handled with exception handlers.
A unique feature of IS-Basic is the ability to have multiple programs simultaneously in memory. Each program has a separate set of global variables and line numbers, but it is possible to call one program from another and pass parameters with the CHAIN statement.
Graphics, sound and I/O ports can be controlled directly from BASIC, so there is a rarely need for POKE and PEEK statements. IS-Basic has the usual commands for drawing dots, lines, circles and ellipses and for filling areas. In addition, Logo-style turtle graphics can be used. Sound commands can be entered into a queue and executed in the background while the program execution continues.
In addition to IS-Basic, several other languages (Forth, Lisp, Pascal, Assembler) were available either on ROM cartridge or on tape. Basic-to-Basic converters could be used to convert BASIC programs from other home computers. Some 40 games were listed in the catalog, from IS and other publishers.[5] IS-DOS, the CP/M compatible operating system opened access to the wide range of CP/M programs that were available at that time.
After the home computer market in the UK took off with the launch of the Sinclair ZX Spectrum in 1982, a Hong Kong trading company called Locumals decided to commission Intelligent Software in the UK to develop a home computer. The head of Intelligent Software was David Levy, an international chess player.
During development the machine had the codename DPC, standing for damp-proof course, to throw off potential competitors in case anyone left the development plans on a bus. The machine was also known by the names Samurai, Oscar, Elan and Flan before the Enterprise name was finally chosen.[6]
Emulating Amstrad's AMSOFT, Entersoft was set up to ensure a steady supply of software for the new machine.
Although the machine was announced to the press in September 1983, it did not go on sale until April 1984, at which point some 80,000 machines were pre-ordered. Unfortunately machines did not ship until 1985, by which point the competitive environment was much worse for Enterprise, as the UK home computer market had become dominated by the ZX Spectrum, Commodore 64, Amstrad CPC and Acorn BBC Micro.
A successor machine, the PW360, was developed in 1986 to compete directly against the Amstrad PCW 8256, but by this time the company was in severe financial difficulties and went under.
Despite being particularly powerful for the time, the machine was not a commercial success. The Amstrad CPC 464 was released before the Enterprise; it included a monitor and cassette recorder and retailed for less.
After the initial manufacturing run of 80,000 units it is not believed that any further units were made, making the Enterprise an extraordinarily collectible item in Europe. When Enterprise (the company) was wound up in Europe, 20,000 units were shipped to Hungary where it appears a strong user community formed.[7]
