Sinclair QL

QL internals (with Minerva ROM fitted)

QL rear view

Motorola 68008 and ZX8301 on the QL's PCB

Bundled Psion application software on Microdrive cartridges

Based on a Motorola 68008 processor clocked at 7.5 MHz, the QL included 128 KB of RAM, which was officially expandable to 640 KB and in practice, 896 KB. It could be connected to a monitor or TV for display. Two built-in Microdrive tape-loop cartridge drives provided mass storage, in place of the more expensive floppy disk drives found on similar systems of the era. Microdrives had been introduced for the Sinclair ZX Spectrum in July 1983, although the QL used a different logical tape format. 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. The supported colours could be stippled in 2×2 blocks to simulate up to 256 colours, an effect which did not copy reliably on a TV, especially over an RF connection. 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 frame buffer, thus allowing double buffering. However, this would have used 64 KB of the standard machine's 128 KB of RAM and there was 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 frame buffer. 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.[3]

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, the ZX8302 originally being intended to perform its functions[4] ran at 11 MHz and acted as a keyboard/joystick interface, RS-232 receive buffer and audio generator.[5]

QDOS, a pre-emptive multitasking operating system primarily designed by Tony Tebby, was included on ROM, as was an advanced structured BASIC interpreter, named SuperBASIC designed by Jan Jones, which was also used as the command-line interpreter. The QL was bundled with an office suite, consisting of a word processor, spreadsheet, database, and business graphics written by Psion.

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

The QL used British Telecom type 631W plugs of similar design to British telephone sockets for serial cables except for QLs built by Samsung for export markets, which had DE-9 sockets. Joysticks connected to the QL with similar type 630W plugs.

Sinclair QL ROM "dongle" – needed to expand the internal 32 KB ROM to 48 KB in early QLs

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 similar to the later TV80 pocket TV, printer and modem. As development progressed it eventually became clear that the portability features were over-ambitious and the specification was reduced to a conventional desktop configuration.[4][6] The electronics were primarily designed by David Karlin, who joined Sinclair Research in summer 1982. The industrial design was done by Rick Dickinson, who already designed the ZX81 and ZX Spectrum range of products. Sinclair had commissioned GST Computer Systems to produce the operating system for the machine, but switched to Domesdos, developed by Tony Tebby as an in-house alternative, 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.[7] [8] The tools developed by GST for the QL would later be used on the Atari ST, where GST object format became standard.

The QL was designed to be more powerful than the IBM Personal Computer, and comparable to Apple's Macintosh.[9] While the CPU clock speed was comparable to that of the Macintosh, and the later Atari ST and Amiga, the 8-bit databus and cycle stealing of the ZX8301 gate array limited the QL's performance. At the time of the rushed launch, on 12 January 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.[4]

Due to its premature launch, the QL was plagued by a number of problems from the start. Early production QLs were shipped with preliminary versions of firmware containing numerous bugs, mainly in SuperBASIC. Part of the firmware was held on an external 16 KB ROM cartridge also known as the "kludge" or "dongle", until the QL was redesigned to accommodate the necessary 48 KB of ROM internally, instead of the 32 KB initially specified.[4] 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 the Samsung Microdrives in particular working perfectly even after almost 17 years of service; 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 QL's CPU, ZX8301 and ZX8302 ASICs and Microdrives 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 addition of a telephone handset at one end of the keyboard, and rudimentary Computer-Telephony Integration (CTI) software.[10] This 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 1980s they were used in bingo halls to allow a country wide networked bingo game.[11]

Linus Torvalds has attributed his eventually developing the Linux kernel, likewise having pre-emptive multitasking, in part to having owned a Sinclair QL in the 1980s. Because of the lack of support, particularly in Finland, Torvalds became used to writing his own software rather than relying on programs written by others.[12] His frustration with the Sinclair led, years later, to his purchasing a more standard IBM PC compatible on which he would develop Linux.

• Sinclair QL Software

Wikimedia Commons has media related to Sinclair QL.

• Dilwyn Jones's QL pages – Well maintained site with comprehensive QL related information and a huge software download library.
• THE REPOSITORY of the Sinclair QL Preservation Project – Well maintained project with valuable Sinclair QL related information and software.
• "Sinclair's 1984 big shot at business: The QL is 30 years old". The Register.