comp.sys.sinclair FAQ

The summaries below are intended to provide a brief introduction to many of the original Sinclair and Timex Computers introduced throughout Europe and North America, with links to more detailed information where appropriate. A list of popular peripherals is also available. A very complete history of Sinclair Research and their products is available from Planet Sinclair.

Sinclair Computers:
Sinclair Research produced several different home computers, starting in the late 1970s and continuing into the middle/late 1980s (following the sale of rights to Amstrad PLC). The models covered immediately below are the most well-known or frequently discussed in comp.sys.sinclair - entries for the early systems (Science of Cambridge MK-14, ZX80, ZX81) and the other models (Quantum Leap, Cambridge Z88) will be expanded during later revisions. In the interim, please refer to the SinclairFAQ home page for links to further information regarding these systems.

• Science of Cambridge MK-14
  Please refer to the current Science of Cambridge MK-14 FAQ, maintained by Paul Robson, for details of this machine.
  
  
• ZX80
  
  
• ZX81
  Please refer to the current ZX81 FAQ.
  
  
  • Documentation:
    • ZX81 BASIC Programming Manual.
    • ZX81 Service Manual and Assembly Instructions (.pdf).
      
      
• ZX Spectrum 16K / 48K / +
  It is fair to say that, for many people, the ZX Spectrum was 'the' home computer of the 1980s. Certainly one of the most popular machines, it was the first introduction to computing for countless schoolchildren and adults alike. Previous Sinclair machines, particularly the ZX80 and ZX81 had been extremely popular, but being supplied primarily as home-build kits, were aimed more at the enthusiast market than any other.
  
  The ZX Spectrum, however, was marketed firmly at the home user when attempts at introducing it to educational institutions largely failed. Although criticism was wide for the machine (the keyboard, in particular, was derided by many) in the press of the time, the 'man-in-the-street' didn't care and bought the ZX Spectrum in vast numbers, originally by mail order only. The introduction to high street stores once production had increased sufficiently to meet the demand (enormous delays hampered the machine at launch) solidified the market-share afforded Sinclair even further. A huge software industry was founded around the popularity of the machine, with many companies founded in the 1980s still in business today producing software for modern systems.
  
  The ZX Spectrum + was introduced in 1984 as a 'rolling' upgrade to the ZX Spectrum. The essential differences are that the keyboard is significantly improved, though still membrane based, and bears resemblance to the design developed for the QL - they are not the same, but share similarities. Additional keys were added to allow direct access to 'Extended' mode, for example, and a 'Reset' button was included, for the first time removing the need to unplug the machine completely to perform a general reset.
  
  To celebrate the launch of the ZX Spectrum +, Sinclair bundled a software package with the machine that provided a good insight into the diverse uses for it - the package included Arcade games, Educational titles, etc. The earlier models could be upgraded to a + either by returning the machine to Sinclair, or by fitting an upgrade kit yourself.
  
  Please see the ZX Spectrum Reference reference page for additional information.
  
  
  • Processor: Zilog Z80A @ 3.5MHz.
  • ROM: 16K.
  • RAM: 16K or 48K
    
    
  • Keyboard: Membrane based (ZX Spectrum + membrane has multiple 'layers');
    • ZX Spectrum 16K / 48K: 40 keys, rubber keycaps.
    • ZX Spectrum +: 58 keys, including shortcuts to common modes & functions ('E', 'G' modes, etc.)
      
      
  • Sound: Internal 40 Ohm TV-type speaker providing 1 channel output.
  • Video: 256 x 192 pixels with 16 available colours.
    
    
  • Power Supply: Part no. varies.
    • Input: 240V AC, 50Hz
    • Output: 9V DC, 1.4A
    • Centre Polarity: -ve (inner diameter is 2.5mm)
      
      
  • Documentation:
    • ZX Spectrum Introductory Manual.
    • ZX Spectrum Basic Programming Manual.
    • ZX Spectrum to ZX Spectrum Plus Upgrade Kit (instructions).
    • ZX Spectrum 48K Service Manual (.pdf).
      
      
• ZX Spectrum 128K / +2 / +2A and +3
  Each of the 128K models is described below. The common specifications are listed for each, with links to original documentation (where available) provided. Technical information for many of these models is provided on the 128K Reference page.
  
  ZX Spectrum 128K:
  Originally developed by Investronica (Spain), the ZX Spectrum 128K was the first 'new' computer to be launched since the original machine was released in 1982. The ZX Spectrum 128K had a "128K" flash in the bottom right-hand corner, and a large heatsink running the full depth of the machine. The most striking external difference between the 128K and ZX Spectrum + is the numeric keypad - this was not included with models later introduced to the UK (it was to be offered as an option), but was standard on the Spanish machine.
  
  
  • Processor: Zilog Z80A @ 3.54690MHz.
  • ROM: 32K (2 x 16K pages).
  • RAM: 128K (8 x 16K pages).
    
    
  • Keyboard: 58 plastic keys.
  • Sound: AY-3-8912 sound chip providing 3 channel / 8 octave sound and internal 40 Ohm TV-type speaker. Sound can also be played through TV speaker.
  • Video: 256 x 192 pixels with 16 available colours. RGB output available.
    
    
  • Power Supply: Part no. varies.
    • Input: 240V AC, 50Hz
    • Output: 9V DC, 1.85A
    • Centre Polarity: -ve
      
      
  • Documentation:
    • ZX Spectrum 128K Introductory Manual.
    • ZX Spectrum 128K Technical Manual (.pdf).
      
      
  Internally, the ZX Spectrum 128K was quite different to the earlier models - a new sound chip had been incorporated, an RGB video output added, and a MIDI interface built-in. The ZX Spectrum 128K was introduced in Spain in 1985 and the UK in 1986.
  
  ZX Spectrum +2:
  The ZX Spectrum differs markedly from the earlier Sinclair machines, both in style and function. Introduced after the sale of Sinclair Research interests to Amstrad PLC, this model features a built-in cassette recorder and two Joystick ports. The case was completely redesigned (now grey in colour) and the 'Keywords' removed from the keycaps for the first time.
  
  
  • Processor: Zilog Z80A @ 3.54690MHz.
  • ROM: 32K (2 x 16K pages).
  • RAM: 128K (8 x 16K pages).
    
    
  • Power Supply: Part no. varies.
    • Input: 240V AC, 50Hz
    • Output: 9V DC, 2.1A
    • Centre Polarity: -ve
      
      
  ZX Spectrum +2A:
  Essentially a redesign of the +2, this model can be distinguished from the earlier machine by colour (initially). Rather than being grey, it is black. Internally, the +2A is closely related to the +3 model; in essence, the disk drive from the +3 was removed and replaced by the cassette recorder used in the earlier design.
  
  ZX Spectrum +3:
  
  • Processor: Zilog Z80A @ 3.54690MHz.
  • ROM: 64K (4 x 16K pages).
  • RAM: 128K (8 x 16K pages).
    
    
  • Power Supply: Part no. varies.
    • Input: 240V AC, 50Hz
    • Output:

          ---u---
        /         \
       / +5    -12 \
      |      0      |
       \ +5    +12 /
        \   +12   /
          -------

      The 5V line is rated at 2A, the +12V at 700mA (200mA for the +2A) and the -12V at 50mA.
• Quantum Leap
  Please refer to the current QL FAQ for further information.
  
  
  • Documentation:
    • QL User Guide (.pdf).
    • QL Service Manual (.pdf).
    • QL Service Manual (HTML).
      
      
• Cambridge Z88
  The Z88 was the first computer developed and marketed by Sir Clive Sinclair under the Cambridge Computer company name, established following the sale of Sinclair Research to Amstrad PLC in early 1986.
  
  The Z88 is very elegant in design, and is remarkably compact in size. A slim LCD display is built-in, providing 64x640 pixel output with variable contrast. The Z88 will operate for approximately 20 hours on a single set of batteries, with a standby time of around a year.
  
  The machine may be operated laying flat on a desk or table, or can be tilted towards the user at an angle of 12.5 degress by extending a retractable foot on the underside of the chassis, making the Z88 a very comfortable machine to use for extended periods of time and in a variety of lighting conditions.
  
  
  • Documentation:
    • Z88 User Manual
  
  Dennis Gröning maintains one of the largest Z88-related sites available. Many utilities, reference and technical documents can be downloaded, and an extensive links section is provided.

Timex Computers:
Sinclair products were distributed throughout certain European and North America by Timex. In general, these machines were fully compatible with their UK equivalents, but some important alterations were made to suit the particular markets they were developed for which leads to some interesting differences, and some incompatibility. A list of models is given below, with key systems being more fully documented on the Timex reference page.

• Timex TS1000
  The TS1000 is the North American version of the ZX81. The only significant differences between the two machines are that, rather than having only 1K of RAM, the TS1000 has 2K, some additonal case sheilding (added to meet FCC regulations), and a channel selector on the bottom of the machine for compatibility with a wide range of TVs.
  
  Originally available by mail-order only, this machine sold in huge quantities until the mass market availability of competing systems from Commodore, Texas Instruments, etc. took over. The TS1000 is compatible with the ZX81, and many common peripherals. The expansion port used on the TS2068 was based on the one used in the TS1000, rather than the ZX Spectrum.
  
  
  • Documentation:
    • TS1000 User Manual.
    • ZX81 / TS1000 Service Manual & Assembly Instructions.
    
    
• Timex TS1500
  Operationally identical to the TS1000 / ZX81, the TS1500 was released as an 'interim' model in place of the never-released TS-2000. Essentially a with 16K of memory built-in, this machine has a case design very similar to that of the ZX Spectrum (the TS1500 is Silver-Grey, rather than Black), and features the rubber keyboard from those models laid out like a TS1000 / ZX81. The TS1016 memory upgrade can be connected via the expansion port to increase the memory size to 32K.
  
  
• Timex TS2068
  The TS2068 was introduced to North America in late 1983 as an enhanced version of the original ZX Spectrum. Despite both the hardware and software being substantially different to the original ZX Spectrum, almost full software compatibility can be achieved by use of a Spectrum emulator cartridge plugged directly into the dock port of the machine. Without the emulator, less than 10% of original software could be expected to work directly on the TS2068 - this figure rises to nearly 100% with the emulation cartridge installed.
  
  The TS2068 has two Joystick interfaces built in to the machine (one on each side), although these are incompatible with the popular Kempston or Cursor interface types. Extensions to Sinclair BASIC were added, allowing access to the Joystick ports and the upgraded sound chip (AY-3-8912) The keyboard was improved, having firm plastic keys rather than the rubber ones used on the original Spectrum, with a full-size space bar and dedicated break key. Physically much larger than the original Spectrum, the TS2068 was the same Silver-Grey colour as the earlier TS1500.
  
  Timex Computer left the market in early 1984, and the machine was withdrawn from sale in the US - much of the remaining inventory was shipped to South America. Zebra Systems, based in NYC, imported modified TC2068s to the States and continued to sell them after the demise of Timex Computer. Timex also introduced the TS2068 design as the TC2068 throughout continental Europe, where it continued to be very popular for several years.
  
  
  • BASIC: An extended version of Sinclair BASIC, with support for the additional hardware features of the TS2068. A BASIC reference page has been added to this FAQ which describes the additional commands available.
    
    
  • Edge Connector: The edge connector on the TS2068 is based on the one used in the TS1000 and TS1500, and is not directly compatible with peripherals originally produced for the ZX Spectrum, although many vendors produced convertors that allow common devices to be connected.
    
    
  • Memory: 48K RAM, 24K ROM. Three internal 64K memory banks; 'HOME' - 16K ROM/48K RAM, 'EXROM' - 8K ROM and 'DOCK' - Reserved for use with ROM Cartridges. The memory is bankswitched in 8K chunks.
    
    
  • Processor: 3.52800MHz Zilog Z80A.
    
    
  • Sound Chip: AY-3-8912.
    
    
  • Video Resolutions / Screen Modes:
    Mode 1: 256x192 Pixels, 24 rows with 32 characters - Uses D_FILE_1 (Hex: 4000-57FF, Dec: 16384-22527) and A_FILE_1 (Hex: 5800-5AFF, Dec: 22528-23296)
    
    Mode 2: 512x192 Pixels, 24 rows with 64 characters. The INK colour is determined based on the PAPER colour selected. BRIGHT and FLASH are not supported.
    
    Mode 3: Operationally the same as Mode 1, but uses D_FILE_2 (Hex: 6000-77FF, Dec: 24576-30719) and A_FILE_2 (Hex: 7800-7AFF, Dec: 30720-31487) instead.
    
    Mode 4: 'Ultra High Color Resoluton' mode uses D_FILE_1 to define pixel data (as with Mode 1) but holds attribute values in D_FILE_2 - this contains 8 times as much memory as A_FILE_1, allowing an attribute byte to be assigned to each row of pixels within each character.
    
    
  • Video Output: RF (antenna) and Composite (line) video outputs are provided, with RGB output being available through the edge connector. If the RGB output is used, BRIGHT is ignored.
    
    
  Additional information for the TS2068 is available in the Timex Reference section of this FAQ, which you may want to read in conjunction with the Timex TS2068 Technical Manual.
  
  
• Timex TC2048
  The Timex TC2048 was introduced by Timex (Portugal) as either an 'upgraded' ZX Spectrum, or 'downgraded' TC2068, depending on how you choose to view it. It is virtually 100% compatible with the ZX Spectrum (the edge connector is slightly different). Although the AY sound chip and cartridge port from the TC2068 have been removed, the additional display modes are retained. A Kempston-compatible Joystick port is built-in.
  
  Internally, the ROM used is almost identical to that of the ZX Spectrum, with only a few differences at particular addresses. These do not appear to significantly impede software intended for the ZX Spectrum and, for all practical purposes, the TC2048 can be considered to be around 99% compatible with the UK machine in this regard. Several emulators provide support for the TC2048, including vbSpec, Fuse, etc.
  
  Note: The TS-2048 was developed by Timex in the US as an alternative to the TS2068, but was never released. The TC2048 developed by Timex (Portugal) is not simply the same machine 'repackaged', but a different design altogether.
  
  
• Timex TC2068
  A PAL variant of the TS2068 introduced to European markets not controlled by Sinclair Research by Timex Portugal. Visually identical to the TS2068 (apart from the "PAL" flash on the lower left of the machine) the TC2068 is internally quite different from the US-developed machine.
  
  The significant differences between these designs are the introduction of the ZX Spectrum compatible edge connector from the TC2048, an "official" ZX Spectrum emulation cartridge - a TC2048 ROM, a PAL video output, and extensions to Sinclair BASIC that provide access to the additional screen modes available on the machine from within BASIC programs. The enhanced BASIC is known as BASIC 64. Versions of the TC2068 were exported to Poland (with black cases, rather than silver), and imported to the US by Zebra Systems directly.