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From Wikipedia, the free encyclopedia
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 flat-screen CRT display and internal 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.
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. 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. 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.
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