Spotters Guide to the Sinclair ZX Spectrum

ZX82? No, it’s called ZX Spectrum

Released in 1982 by Sinclair Research Ltd. and following on from the huge success of his previous home micros the ZX80 and ZX81 was Sir Clive Sinclair’s first colour computer the Sinclair ZX Spectrum (code-named ZX82 during development). Gone was the black and white, the Spectrum now boasted an 8 colour palette and 2 brightness modes. Gone was the silence, some might say this was not a good thing, early Spectrums could quite literally BEEP and that was it. Gone was the touch sensitive keyboard, now replaced by the (in)famous ‘dead flesh’ rubber keys but still retaining the innovative Sinclair one touch-one word programming system implementing Sinclair BASIC. This system not only saved time (once you got used to the key combinations) but also reduced the amount of memory needed as each word only took up one byte in memory.

The fact this was retained is a clue as to what Sir Clive originally intended his first colour computer to be, not the games machine as we all now remember it, but instead (and like the ZX81) a multi-use hobbyists machine which could also be used as a tool for programming. The design of the internal hardware was by Richard Altwasser and the external design of the unit was undertaken by Rick Dickinson, the genius industrial designer already responsible for draughting the ZX80, ZX81 and the following year, the Sinclair FTV1 Flat Screen Pocket TV. For the purposes of this article I will only be listing official Sinclair branded models and not any of the numerous clones that were produced worldwide.

ZX Spectrum 16K and 48K (1982)

Released in 1982, the 16K and 48K ZX Spectrum continued Sinclair’s trend for affordable computing and cost only £125 (later reduced to £99) and £175 (later reduced to £129) respectively. An extra 32K of RAM could be added to the 16K Spectrum in the form of a daughterboard on Issue 1 machines or by way of extra chips on subsequent machines. You had two choices of how this was accomplished, the first being a postal option whereby you mailed your Spectrum off to Sinclair Research and it was returned to you upgraded. The second option was in the true spirit of Sinclair and was in the form of a kit which you soldered in yourself.

Issue 1 machines (top picture) could be distinguished by their lighter grey keys as opposed to later darker blue/grey keys of later issues (six altogether up to the release of the 128K). The famous keyboard itself was of membrane type with a rubber overlay and was designed this way to keep cost down but resulting in it becoming the Spectrum’s greatest weakness with membrane failure being a major fault on these machines. Data transfer was via audio in/out via cassette deck or by way of attaching an Interface 1 and Microdrive(s) (pictured below) to the rear I/O expansion port (edge connector). You could also purchase Interface 2 (pictured below) which had two joystick ports and a port which allowed you to play the limited range of ten ROM cartridges released.

Only 60,000 Issue 1’s were ever produced making it the most sought after rubber keyed ZX Spectrum. Spectrums came with a bundled starter cassette called ‘Horizons’ which could be used in conjunction with the superb instruction manual in order to learn various programming techniques. Various other software bundles were produced for this machine (depending on the vendor) but the famous Sinclair ‘Software Six Pack’ comprising of ‘Horace Goes Skiing’, ‘Make-a-Chip’, ‘Computer Scrabble’, ‘Chess’, ‘Chequered Flag’ and ‘Survival’ was bundled with all original 48K Spectrums.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 16K
RAM: 16KB or 48KB
Sound: (1 channel, 10 octaves)
Ports: Expansion I/O, RF, Ear, Mic
Price at launch: £125 (16K), £175 (48K)

Spectrum Six Pack as bundled with 48K Spectrums

ZX Spectrum 48K with ZX Interface 2 and ROM cartridge

ZX Spectrum 48K with ZX Interface 1 and ZX Microdrive

ZX Spectrum+ (1984)

This release in 1984 which retailed at £179.95, added a keyboard with moving keys to remedy the ‘dead flesh’ feel of the original along with a reset button, but otherwise was just the same computer in a new case. Unfortunately the keyboard was plagued by the same problems as the original 48K Spectrum as it was still just a membrane underneath injection-moulded plastic keys. In fact the problem was reportedly even worse with the new keyboard and failure rates of as much as 30% were reported by some retailers compared to the rubber keyboard failure rate of under 10%. Because they were exactly the same machine, Sinclair introduced an upgrade option where you could buy a case kit and swap out the internal board yourself. The Spectrum + came bundled with a starter cassette and a new-look manual by Dorling Kindersley.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 16K
RAM: 48KB
Sound: (1 channel, 10 octaves)
Ports: Expansion I/O, RF, Ear, Mic
Price at launch: £179.95

ZX Spectrum 128 (1985 Spain, 1986 UK)

My favourite ZX Spectrum and the last model to be developed before the famous Amstrad buyout of the Sinclair brand and computer range in 1986. Code named ‘Derby’ by Sinclair Research, this machine retained the familiar look of the Spectrum + but with the obvious addition of a large heatsink which earned this model the nickname of ‘toast rack’.

The 128 was initially released at the SIMO ’85 trade show in Spain but not in the UK until 1986 (at a price of £179.95) because of Sinclair’s backlog of unsold Spectrum+ computers. A number of improvements (apart from the obvious memory hike) were implemented with this model including; three channel audio via the AY3-8912 chip, an RS-232/MIDI serial port, RGB output and an external keypad (Spain only). Gone was the internal speaker, sound was now played through the television set. Gone also was the one-touch keyword system although by using the new menu on the opening screen you could switch to a 48K mode which in effect emulated the earlier machine. You could also use the menu to go straight to a tape loader, calculator or tape tester (see pic left). Unfortunately, Sinclair missed a few tricks and made the RS-232/MIDI port non-standard and also failed to include joystick ports, even though it was marketed as an “entertainment machine”. The 128 came bundled with a starter cassette and The Neverending Story and Daley Thompsons Supertest by Ocean.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 32KB (16K for 128K mode, 16K for 48K mode)
RAM: 128KB (8 x 16K)
Sound: 3 Channels, 7 Octaves (Yamaha AY-3-8912)
Ports: Expansion I/O, RGB, Keypad, RS232/Midi, RF
Price at launch: £179.95

ZX Spectrum +2 (1986)

After Amstrad’s buyout of Sinclair in 1986, they set to work designing a new ZX Spectrum. The resulting machine was the only Spectrum to have a grey case and now resembled previous Amstrad computers with it’s built-in tape deck and for the first time; a proper fully moving keyboard. Gone was the one-touch-one word keyboard; you now had to type out your words letter by letter, although the startup menu still allowed you to use 48K mode and use keywords (even though you had to guess or memorise from earlier Spectrums just what keys did what!). The menu was now without the ‘tape test’ option and the copyright message was now Amstrad’s own resulting in some incompatibilities with old software and the new ROM (although there were actually very few). Due to lower production costs the price of this new machine had now dropped to £149.00.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 32KB (16K for 128K mode, 16K for 48K mode)
RAM: 128KB (8 x 16K)
Sound: 3 Channels, 7 Octaves (Yamaha AY-3-8912)
Ports: Expansion I/O, RS232/Midi, Keypad, RGB, RF, Sound
Price at launch: £149

ZX Spectrum +2 a/b (1987)

Back to black with the ZX Spectrum +2a/b which was essentially a +3 in a black +2 case with a datacorder instead of the disk drive. In fact, aside from looking aesthetically similar to the +2, this was an entirely new machine, sporting a redesigned motherboard with a much reduced chipset (the same board as the +3 below). All of these internal changes came at a cost though, with the +2a/b models being incompatible with a lot of older software. Other changes were made including some to the I/O Expansion which rendered the ZX Interface 1 (and therefore Microdrives) incompatible with this model.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 64KB (32K for 128K mode, 16K for 48K mode, 16K for +3DOS)
RAM: 128KB (8 x 16K)
Sound: 3 Channels, 7 Octaves (Yamaha AY-3-8912)
Ports: Printer, Expansion I/O, RS232/Midi, Aux (formerly ‘keypad’), RGB, RF, Sound
Price at launch: £199

ZX Spectrum +3 (1987)

Coming to market slightly before the +2a/b was the first Spectrum with a disk drive, albeit (and in typical Amstrad fashion) Amstrad’s own 3″ version and not the more widely adopted 3.5″ FDD. Apart from the disk drive (and disk B port), this machine was almost identical to the +2a/b models released later the same year.

Despite floppy disks being the ‘next generation’ of data storage, the +3 was a flop, most sales still going to it’s +2 brother. Perhaps the necessity of a Multiface 3 to transfer data from tape to disk or lack of support for the disk format resulting in a poor choice of software could be to blame for its lacklustre sales. More likely still, it was the superior Commodore Amiga and Atari ST. Whatever the cause, this remains the final Sinclair ZX Spectrum model produced.

Specifications

CPU: Z80A
Speed: 3.5MHz
ROM: 64KB (32K for 128K mode, 16K for 48K mode, 16K for +3DOS)
RAM: 128KB (8 x 16K)
Sound: 3 Channels, 7 Octaves (Yamaha AY-3-8912)
Ports: Disk B, Printer, Expansion I/O, RS232/Midi, Aux, RGB, RF, Sound, 2 x Joystick ports
3″ Hitachi Floppy Disk Drive – single sided
Price at launch: £249