Sinclair QL

Sinclair QL

Infobox computer
Type = Personal computer
Released = Start date|1984|01|12
Photo =
Discontinued = April 1986
Processor = Motorola 68008 @ 7.5 MHz
Memory = 128 KB (640 KB max.)
OS = Sinclair QDOS
The Sinclair QL (for " Quantum Leap"), was a personal computer launched by Sinclair Research in 1984, as the successor to the ZX Spectrum. The QL was aimed at the hobbyist and small business markets, but failed to achieve commercial success.


The QL was originally conceived in 1981 under the code-name "ZX83", as a portable computer for business users, with a built-in ultra-thin flat-screen CRT display (later released as the TV80, printer and modem. As development progressed, and "ZX83" became "ZX84", it eventually became clear that the portability features were over-ambitious and the specification was reduced to a conventional desktop configuration.cite web|url=|title=The Quantum Leap - to where?|work=Sinclair and the 'Sunrise' Technology|author=Ian Adamson|coauthors=Richard Kennedy|accessdate=2006-12-15] cite web
title=QL and Beyond
author=Rick Dickinson

Based on a Motorola 68008 processor clocked at 7.5 MHz, the QL included 128 KB of RAM (officially expandable to 640 KB) and could be connected to a monitor or TV for display. [1 KB = 1024 B] Two built-in Microdrive tape-loop cartridge drives (first seen as a peripheral for the ZX Spectrum) provided mass storage, in place of the more expensive floppy disk drives found on similar systems of the era. Interfaces included an expansion slot, ROM cartridge socket, dual RS-232 ports, proprietary QLAN local area network ports, dual joystick ports and an external Microdrive bus. Two video modes were available, 256×256 pixels with 8 RGB colours and per-pixel flashing, or 512×256 pixels with four colours (black, red, green and white). Both screen modes used a 32 KB framebuffer in main memory. The hardware was capable of switching between two different areas of memory for the framebuffer, thus allowing double buffering. However, this would have used 64 KB of the standard machine's 128 KB of RAM and there is no support for this feature in the QL's original firmware. The alternative and much improved operating system Minerva does provide full support for the second framebuffer.

Internally, the QL comprised the CPU, two ULAs, (ZX8301 and ZX8302) and an Intel 8049 microcontroller (known as the IPC, or "Intelligent Peripheral Controller"). The ZX8301 or "Master Chip" implemented the video display generator and also provided DRAM refresh. The ZX8302, or "Peripheral Chip", interfaced to the RS-232 ports (transmit only) Microdrives, QLAN ports, real-time clock and the 8049 (via a synchronous serial link). The 8049 (included at late stage in the QL's design, as substitute for a third ULA) acted as a keyboard/joystick controller, RS-232 receive buffer and audio generator.

A multitasking operating system, "QDOS", primarily designed by Tony Tebby, was included on ROM, as was an advanced BASIC interpreter, named SuperBASIC designed by Jan Jones. The QL was also bundled with an office suite (word processor, spreadsheet, database, and graphics) written by Psion. Sinclair had commissioned GST Computer Systems to produce an operating system for the machine, but switched to QDOS, developed in-house, before launch. GST's OS, designed by Tim Ward, was later made available as 68K/OS, in the form of an add-on ROM card. [cite magazine
title=QL Affairs
author=Leon Heller
journal=Your Spectrum
] [ cite web
title=Sinclair QL
work=Binary Dinosaurs
] The tools developed by GST for the QL would later be used on the Atari ST, where GST object format became standard.

Physically, the QL was the same black colour as the preceding ZX81 and ZX Spectrum models, but introduced a new angular styling theme and keyboard design which would later be seen in the ZX Spectrum+.


The QL was the first mass-market personal computer based on the Motorola 68000-series processor family. Rushed into production, the QL beat the Apple Macintosh by a month, and the Atari ST by a year. While clock speeds were comparable, the 8-bit databus and cycle stealing of the ZX8301 ULA limited the QL's performance. However, at the time of launch, on January 12, 1984, the QL was far from being ready for production, there being no complete working prototype in existence. Although Sinclair started taking orders immediately, promising delivery within 28 days, first customer deliveries only started, slowly, in April. This provoked much criticism of the company and the attention of the Advertising Standards Authority.

Due to its rushed development, the QL was plagued by a number of problems from release, particularly bugs in the QDOS operating system and SuperBASIC which led to multiple releases of the firmware. In addition, early production QLs were shipped with an external 16 KB ROM cartridge (infamously known as the "kludge" or "dongle") containing part of the firmware until the QL was redesigned to accommodate the necessary 48 KB of ROM internally, instead of the 32 KB initially specified. The QL also suffered from reliability problems of its Microdrives. These problems were later rectified, by Sinclair engineers, especially on Samsung produced models, as well as by aftermarket firms such as Adman Services and TF Services — to the point where several QL users report their Microdrives working perfectly even after almost 17 years of service (for Samsung QLs) — but in any case much too late to redeem the negative image they had already created.

Although the computer was hyped as being advanced for its time, and relatively cheap, it failed to sell well, and UK production was suspended in 1985, due to lack of demand. After Amstrad acquired Sinclair's computer products lines in April 1986, the QL was officially discontinued. Apart from its reliability issues, the target business market was becoming wedded to the IBM PC platform, whilst the majority of ZX Spectrum owners were uninterested in upgrading to a machine which had a minimal library of games. Sinclair's persistence with the non-standard Microdrive and uncomfortable keyboard did not endear it to the business market; coupled with the machine's resemblance to a ZX Spectrum, they led many to perceive the QL as something akin to a toy. Software publishers were also reluctant to support the QL due to the necessity of using Microdrive cartridges as a distribution medium.

The ICL connection

The QL's CPU, ZX8301 and ZX8302 ULAs and ZX Microdrives also formed the basis of International Computers Limited's (ICL's) One Per Desk (OPD) - also marketed by British Telecom as the Merlin Tonto and by Telecom Australia as the Computerphone. The result of a three-year collaboration between Sinclair Research, ICL and British Telecom, the OPD had the intriguing addition of a telephone handset on one end of the keyboard, and rudimentary Computer-Telephony Integration (CTI) software. [cite web
title=ICL OPD One Per Desk
] This curious machine interested a number of high-profile business customers, including certain divisions of the former UK Customs and Excise Department, but its success was generally limited.In the late eighties they were used in Bingo halls to allow a country wide networked bingo game. [cite web
title=ICL OPD
work=Binary Dinosaurs

Post-1986 developments


After Amstrad abandoned the QL, several companies previously involved in the QL peripherals market stepped in to fill the void.These included CST and DanSoft, creators of the Thor line of compatible systems; Miracle Systems, creator of the Gold Card and Super Gold Card processor/memory upgrade cards and the QXL PC-based hardware emulator; and Qubbesoft, with the Aurora, the first replacement QL mainboard, featuring enhanced graphics modes.cite web
title=QL History FAQ: Hardware
author=Robert Klein

In the late 1990s, two partly QL-compatible motherboards named Q40 and Q60 (collectively referred to as Qx0) were designed by Peter Graf and marketed by D&D Systems. The Q40 and Q60, being based around the 68040 and 68060 CPUs respectively, were much more powerful than the original QL and have the ability among other things (such as multimedia, high resolution graphics, Ethernet networking etc.) to run the Linux operating system. [cite web

Hardware add-ons are still being produced for the original QL mainly by TF Services who supply various hardware and software upgrades.


A few patched versions of QDOS were produced, most notably Minerva which gradually evolved into a completely rewritten operating system, offering improved speed, with multitasking SuperBASIC interpreters. Tony Tebby went on to produce another updated operating system, SMSQ/E, which has continued to be developed for the Sinclair QL and emulators, offering many more features. [cite web
title=QL History FAQ: Firmware
author=Robert Klein


* Linus Torvalds, creator of Linux, owned a Sinclair QL in his youth and used it to learn programming. [cite web
title=Linux Anecdotes
author=Lars Wirzenius

* The QL's Intel 8049 Intelligent Peripheral Controller actually ran at a higher clock speed than the 68008 CPU (11 versus 7.5 MHz).

* When connected to a normally-adjusted TV or monitor, the QL's video output would overscan horizontally. This was reputed to have been due to the timing constants in the ZX8301 chip being optimised for the flat-screen CRT display originally intended for the QL. [cite newsgroup
author=Rupert Goodwins
title=Sinclair Loki Superspectrum
* QLs built by Samsung for export markets had DE-9 sockets for the RS-232 and joystick ports, instead of the unusual and UK-specific BT630W (similar to BS 6312) sockets found on UK-built QLs.

* External QL Microdrives appeared on QL accessory pricelists but were never produced. However, ZX Microdrives could be connected to the external Microdrive interface and performed flawlessly on a QL (actually offering higher reliability than the built-in ones)Fact|date=June 2008.

See also

*Sinclair QL Software

External links

* [ Dilwyn Jones's QL pages] - General QL information and software downloads
* [ Thierry Godefroy's Sinclair QL and QDOS compatible systems site]
* [ Binary Dinosaurs: QL peripherals gallery]
* [ Sinclair QL Service Manual, issue 3, October 1985]
* [ QL-Users Mailing List]

Emulators & Support

* [ RWAP Software - Software, second hand items and keyboard membranes]
* [ RWAP Adventures - Adventure programs for the Sinclair QL and ZX Spectrum]
* [ QBranch]
* [ Jochen Merz Software]
* [ Sinclair QL Homepage]
* [ TF Services (Tony Firshman) Spares, repairs and addons for the QL]
* [ Davide Santachiara web page]
* [ Q-emuLator Sinclair QL emulator for Windows and Mac OS]
* [ QPC emulator for DOS and Windows (uses QDOS successor SMSQ/E)]
* [ uQLx emulator for Unix]
* [ QL2K - Sinclair QL Emulator for Windows 2000/XP]


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