zx spectrum

The Sinclair ZX Spectrum was a small home computer released in the United Kingdom in 1982 by Sinclair Research. Based on a Zilog Z80 CPU running at 3.50 MHz, the Spectrum came with either 16 KB or 48 KB of RAM (an expansion pack was also available to upgrade the former). The hardware designer was Richard Altwasser of Sinclair Research and the software was written by Steve Vickers (on contract from Nine Tiles Ltd, the authors of Sinclair BASIC). Sinclair's industrial designer Rick Dickinson was responsible for the machine's outward appearance. Originally dubbed the ZX82, the machine was later renamed the "Spectrum" by Sinclair to highlight the machine's colour display, compared to the black-and-white of its predecessors the ZX80 and ZX81.

Description

Video output was to a TV, for a simple colour graphic display. The rubber keyboard (on top of a membrane, similar to calculator keys) was marked with Sinclair BASIC keywords, so that pressing, say, "G" when in programming mode would insert the BASIC command GOTO. Programs and data were stored using a normal cassette recorder. The Spectrum's video display, although rudimentary by today's standards, was perfect at the time for display on portable TV sets, and didn't present much of a barrier to game development. The text mode display was 32 columns × 24 rows of characters from the Spectrum Character Set, with a choice of 8 colours in either normal or bright mode, which gave 15 shades (black was the same in both modes). The graphics resolution was 256×192 with the same colour limitations. The Spectrum had an interesting method of handling colour; the colour attributes were held in a 32×24 grid, separate from the text or graphical data, but was still limited to only two colours in any given character cell. This led to what was called colour clash or attribute clash with some bizarre effects in arcade style games. The Spectrum was the first mainstream audience home computer in the UK, similar in significance to the Commodore 64 in the USA (the C64 also being the main rival to the Spectrum in the UK market). An enhanced version of the Spectrum with better sound, graphics and other modifications was marketed in the USA by Timex as the TS2068.

Models

ZX Spectrum (1982)

Released by Sinclair in 1982 and available with either 16 KB (125, later 99) or 48 KB (175, later 129) of RAM and 16 KB ROM. Remembered for its rubber keyboard and diminutive size. Owners of the 16 K model could purchase an external 32K RAMpack that mounted in the rear expansion slot. Also available was an internal 32K RAM update, which consists of 8 dynamic RAMs and few TTL chips. As with the ZX81, "RAMpack wobble" caused by poor connection with the expansion was the bane of many users, causing instant crashes and sometimes ULA or CPU burnout.

ZX Spectrum+ (1984)

The 48K Spectrum gets a much needed solid keyboard and reset button, retailing for 180. An upgrade package for older machines was also available.

ZX Spectrum 128K (1986)

The last Spectrum to be produced by Sinclair (although developed by Investronica of Spain) and based on the Spectrum+. New features included three-channel audio via the AY-3-8912 chip, MIDI compatibility, 128 KB of paging RAM, an RS-232 serial port and an RGB monitor output. The 128 model saw a second 16 KB ROM chip hosting the new 128 K editor and enhancements with both ROM's and additional RAM using bank switching techniques to bypass the 64K memory limit of the Z80 processor.

ZX Spectrum +2 (1986)

Shortly after Amstrad's buyout of Sinclair Research in 1986 came the ZX Spectrum +2. It featured a new casing coloured grey, distinguishing itself from the familiar black of previous Spectrums. The new case also integrated a new spring loaded keyboard, dual joystick ports, and a built-in cassette recorder dubbed the "Datacorder" (like the Amstrad CPC 464). Production cost cutting saw the retail price drop to 139-149. Aside from the tape drive, revised keyboard and casing the +2 was essentially the same as the 128 model.

ZX Spectrum +3 (1987)

Amstrad produced disk version based on the +2 but featuring a built-in 3-inch floppy disk drive (like the Amstrad CPC 6128). Most models featured distorted sound thanks to a design fault later rectified in the "4.1 ROM" model. Retailed for 249 then later 199 and the only model capable of running CP/M without additional hardware. The +3 saw the addition of two more 16 K ROM's, now physically implemented as two 32K chips, one home to the second part of the reorganised 128 K ROM, the other hosting the +3's disk operating system. Such core changes brought incompatibilities:

Removal of lines on the edge connector - Caused many external devices problems, some such as the VTX5000 model could be used via a FixIt device
Reading a non-existent IO port no longer returned the last attribute - Caused some games such as Sabre Wulf to be unplayable
Memory timings - Some of the RAM banks were now contended causing high-speed colour-changing effects to fail

ZX Spectrum +2A / +2B (1987)

The +2A was produced to homogenize Amstrad's range. Although the case reads "ZX Spectrum +2", the +2A/B is easily distinguishable from the original +2 as the case was restored to the standard Spectrum black. The +2A was derived from Amstrad's +3 4.1 ROM model, hosting a new motherboard which vastly reduced the chip count, integrating many of them into a new ASIC. The +2A replaced the +3's disk drive and associated hardware with a tape drive, as in the original +2. Originally, Amstrad planned to introduce an additional disk interface, but this never appeared. The only difference between the +2A and +2B was a move in manufacturing from Hong Kong to Taiwan.

Clones

Sinclair licensed the Spectrum design to Timex in the USA who produced their own, largely incompatible, derivatives. In the UK Spectrum peripheral vendor Miles Gordon Technology (MGT) released the SAM Coup as the natural successor with some Spectrum compatibility however the Commodore Amiga and Atari ST had taken hold of the market by this point leaving MGT in eventual receivership. Many unofficial Spectrum clones were produced, especially in Eastern Europe and South America. Some of them are still being produced such as the Sprinter from Peters Plus Ltd. Russian clones include the Hobbit, Pentagon and Scorpion. Brazilian clones include TK-90X and TK-95 from Microdigital.

Peripherals

Several peripherals for the Spectrum were marketed by Sinclair: the printer was already on the market, as the Spectrum had retained the protocol for the ZX81's printer. The Interface 1 added a standard RS-232 serial port, a proprietary format local area networking port, and the ability to connect up to eight ZX Microdrives – somewhat unreliable but speedy tape-loop storage devices (later used in a revised version on the Sinclair QL, whose storage format was electrically compatible but logically incompatible with the Spectrum's). Sinclair also released the Interface 2 which added two joystick ports and a ROM cartridge port. There were also a plethora of third-party hardware addons. The more well-known of these included the Kempston joystick interface, the Currah Microspeech unit (speech synthesis), and the Multiface (snapshot and disassembly tool), from Romantic Robot. There were numerous disk drive interfaces, including the Opus Discovery and the DISCiPLE/PlusD from Miles Gordon Technology. During the mid-80s, the company Micronet800 launched a service allowing users to connect their ZX Spectrums to a network known as Prestel. This service had some similarities to the Internet, but was proprietary and fee-based.

Software

The Spectrum family enjoyed a very large software library of at least 20,000 titles. Despite the fact that the Spectrum hardware was limited by most standards, its software library was very diverse, including compilers, databases, word processors, drawing and painting tools, and, of course, many games. A number of current leading games developers and development companies began their careers on the ZX Spectrum, including Peter Molyneux (ex-Bullfrog Games), Dave Perry of Shiny Entertainment, and Ultimate Play The Game (now known as Rare, maker of many famous titles for Nintendo game consoles). Other prominent games developers include Matthew Smith (Manic Miner, Jet Set Willy), and Jon Ritman (Match Day, Head over Heels). Most Spectrum software was originally distributed on audio cassette tapes. The software was encoded on tape as a sequence of alternating pitches, similar to the sounds of a modern day modem. On average, a 48 K program would take about 5 minutes to load. The Spectrum was intended to work with almost any cassette tape player, and despite differences in audio reproduction fidelity, the software loading process was quite reliable. In addition to tapes, software was also distributed through print media, fan magazines, or books. The prevalent language for distribution was the Spectrum's BASIC dialect. The reader would type the software into the computer by hand, run it, and save it on tape for later use. The software distributed in this way was in general simpler and slower than its assembly language counterparts, and lacked graphics. There was a vibrant scientific community built around such software, ranging from satellite dish alignment programs, to school classroom scheduling programs. One unusual software distribution methods was a TV show (in Eastern Europe) where the hosts would describe a program, instruct the audience to connect a cassette tape recorder to the TV, and then broadcast the program over the airwaves in audio format. As audio tapes have a limited shelf-life, most Spectrum software has been digitized in recent years and is available for download in digital form. One popular program for digitizing Spectrum software is Taper: it allows to connect a cassette tape player to the IN port of a Sound Blaster or (through a simple home-built device) to the parallel port of a PC. Once in digital form, the software can be executed on one of many existing emulators, on virtually any platform available today. The Spectrum enjoys a vibrant, dedicated fan-base. Since it was cheap and simple to learn to use and program, the Spectrum was the starting point for many programmers and technophiles who remember it with nostalgia. The hardware limitations of the Spectrum imposed a special level of creativity on game designers, and for this reason, many Spectrum games are very creative and playable even by today's standards.