Sinclair QL [Sinclair]

The Sinclair QL (Quantum Leap) was unveiled on January 12, 1984, and was intended to be Sir Clive Sinclair's next major triumph following the ZX Spectrum. On paper, the concept read impressively: a 32-bit home computer featuring a true multitasking operating system, professional office software, and networking capabilities for under £400 (specifically £399—a fraction of what Apple was charging for the Macintosh, which was released that same month). With this device, Sinclair aimed to make a direct push into the business market, where IBM and Apple had previously held sway.

Unfortunately, the reality was quite different. The QL hit the market nearly a year ahead of schedule—primarily to beat Apple and the Atari ST, which was expected the following year, to the punch. At the time of the press launch, not a single fully functional prototype existed; nevertheless, Sinclair immediately began accepting orders, promising delivery within 28 days. The first units finally began trickling out to customers—albeit sluggishly—starting in April 1984; consequently, the British computer press soon ceased interpreting the acronym QL as "Quantum Leap," opting instead for the mocking translation "Quite Late." Even the British advertising watchdog, the ASA, took an interest in the affair.

The Kludge – When the ROM Doesn't Fit in the Case

To ensure that anything could be shipped at all, Sinclair resorted to a stopgap measure that remains legendary to this day: for the initial units featuring the **Issue 4 mainboard**, the operating system was simply not yet sufficiently finalized to fit within the planned 32 KB of ROM. The excess code was unceremoniously offloaded onto an additional **16 KB ROM module** that protruded from the back of the casing. The trade press mockingly dubbed this makeshift solution a "Kludge" or "Dongle." It was not until later board revisions (Issues 5, 6, and 7) that the units shipped with the full **48 KB of ROM** housed entirely within the casing; owners of the very first units were subsequently able to exchange their machines free of charge.

Inner Values

Inside lies a Motorola 68008 clocked at 7.5 MHz—essentially the same 32-bit processor as the 68000 found in the Atari ST and Amiga, albeit with its external data bus reduced to 8 bits. This is precisely the "crippled processor" I had already criticized in the original version of this article: the 68008 cost less and required simpler memory chips, but due to its narrow bus, it was significantly slower than its larger siblings. Furthermore, the ZX8301 ULA regularly stole clock cycles from the processor for screen generation (cycle stealing), which further depressed its effective performance.

On the side, two custom ULAs handle the heavy lifting: the aforementioned ZX8301 is responsible for graphics output, while the ZX8302 ("Peripheral Chip") manages the Microdrives, serial interfaces, networking, and real-time clock. An Intel 8049 serves as a co-processor, handling the keyboard and—very rudimentary—sound generation.

The graphics subsystem features two modes: 512 × 256 pixels with 4 colors for word processing, or 256 × 256 pixels with 8 colors for somewhat more colorful applications. There are no sprites or hardware scrolling—the QL was clearly not intended as a gaming machine.

QDOS and SuperBASIC

However, the truly fascinating aspect of the QL lay in its software. With QDOS, Tony Tebby had written a preemptive multitasking operating system that was far ahead of its time. Running multiple programs simultaneously, switching between windows, and printing in the background while continuing to work in the foreground—in 1984, this was absolutely extraordinary for a home computer. Added to this was SuperBASIC by Jan Jones—a structured BASIC featuring named procedures, functions, and local variables, and free from the rigid requirement of line numbers. For anyone emerging from the "GOTO hell" of Spectrum BASIC, this felt like true liberation.

Also included was the famous Psion Suite on two Microdrive cartridges—four full-featured applications that later, in a slightly modified form, also made their way to the PC under the name *Psion Xchange*:

• Quill – Word Processing with True WYSIWYG Display
• Abacus – Spreadsheet
• Archives – Database with its own query language
• Easel – Business Graphics

It was precisely this package that captivated me back then. I gained my first experience with word processing and spreadsheets using it—long before such programs became the standard on the Atari ST or PC.

Microdrives – The Eternal Achilles' Heel

The two built-in Microdrives were intended as an affordable alternative to floppy disk drives. They consist of tiny continuous-loop tapes housed in plastic cartridges, capable of storing around 100 KB per cartridge—and, notably, they load significantly faster than a standard cassette. They were already familiar as a peripheral device for the ZX Spectrum; with the QL, however, they were now built directly into the system.

Theoretically, it was a nice idea. In practice, however, the Microdrives were the QL's Achilles' heel: sensitive to dust, increasingly unreliable with age, and—with their awkward 100 KB of storage capacity—hardly competitive against 720 KB floppy disks. Anyone wishing to work seriously with the QL could scarcely do without an external floppy interface.

The Personal Story

Unfortunately, I can no longer recall exactly why I traded in my ZX Spectrum for a QL back then. It was likely due to a fascination with the included office software and the appeal of being able to do something "proper" with the computer. I purchased my QL from a small systems house located near where I lived.

Obtaining software for the QL in Germany was significantly more difficult than it was for the Spectrum. At the time, I subscribed to an English QL magazine just to get access to listings and news about the platform. I had to program much of it myself—which, in retrospect, was probably the main reason I learned more on that computer than I did on the Spectrum before it.

Nevertheless, my time with the QL was relatively brief: In the summer of 1987, upon graduating from school, I received my Atari 1040 STFM—and with that, the QL chapter came to a close for me, at least for the time being. In retrospect, the QL served as the link between the 8-bit world of the Spectrum and the 16/32-bit world of the ST.

A little trivia gem on the side

In 1987, a certain Linus Torvalds used his savings—supplemented by a loan from his father—to buy his very first computer: a Sinclair QL. On it, he first wrote his own editor and assembler, then a Pac-Man clone named *Cool Man*, and finally a driver for a floppy disk interface, as he found the included one to be too slow. In the process, he discovered several bugs in QDOS. A few years later, working on a 386 PC, he wrote the first lines of code for a project he would later name *Linux*. Without the QL, Linux would likely not exist in its current form.

Extensions – When the Community Takes Over

After Sinclair discontinued the QL in April 1986—having sold only around 150,000 units (Amstrad had acquired Sinclair and saw no remaining market)—a very active community took the helm. Foremost among them was the British company Miracle Systems, which kept the QL alive for more than a decade:

• The Trump Card provided 768 KB of additional memory (totaling 896 KB—exceeding the official 640 KB limit), a floppy interface, and Toolkit II on a single card connected to the expansion port.
• The Gold Card replaced the 68008 with a 16 MHz 68000, and added 2 MB of RAM, a floppy interface with support for DD, HD, and even ED disks, as well as a battery-buffered real-time clock—all without requiring any internal modification to the QL.
• The Super Gold Card capped it all off in 1993 with a 24 MHz 68020 processor, 4 MB of RAM, and a Centronics interface. With this, a QL suddenly became a thoroughly serious computer.

In addition, there were alternative operating system ROMs (Minerva, later SMSQ/E), hard drive interfaces, and even complete QL replicas housed in PC cases.

Sinclair QL Technical Specifications

My copy today

Well-preserved—and, above all, "unmodified"—QLs have by now become a genuine rarity on eBay. A few years ago, I was lucky enough to win just such a specimen at auction. Included with it was a functioning 512 KB memory expansion for the expansion port, featuring a bus passthrough.

During my first extensive test, I noticed that several individual keys were no longer responding. The cause was quickly identified: the keyboard membrane inside the QL—as was the case with so many Sinclair devices of that era—had become brittle over the years. Fortunately, new membranes are still available as reproduction parts, and replacing one is a manageable task if you have a little patience (see my separate repair article).

I have also now successfully got the two disk interfaces in the collection up and running—an *XDISK Wolf Computer V1.00* from 1987 and a *QDOS Disc Controller V1.16* from 1984. This was made possible by Ben from Belgium, who still builds compatible 3.5-inch dual-drive units for the QL, as well as Rich Mellor, whose assistance helped clarify exactly which drive was required. I have documented the details—including the most important QDOS disk commands and a neat trick for transferring PC software onto a QL diskette using QEmuLator—in a dedicated article on using disk drives with the QL.

Modern Extensions from the Community

What makes the QL particularly fascinating to me today is the small yet remarkably productive community that continues to develop new hardware for the machine. Over the past few years, I have added several of these expansions to my collection, presenting each one individually and in detail:

• QL-SD – an SD ​​card interface by Peter Graf that finally liberates the QL from the straitjacket of Microdrive cartridges. With it, half of the world's entire QL software archive fits onto a single card.
• QubIDE – an AT/IDE hard drive interface, originally developed by Zeljko Nastasic in 1996 and distributed by Qubbesoft. It retrofits the QL into a proper workstation complete with a hard drive.
• Tetroid Disk Interface CF – a modern reproduction of a disk interface that additionally features a Compact Flash slot, thereby combining floppy and mass storage access in a single device.
• mICE —the Icon Controlled Environment by Eidersoft—was an early attempt in the mid-80s at an icon-based interface for the QL, stylistically closely resembling Digital Research's GEM. Today, a small adapter board even makes it possible to connect a USB mouse.
• QL-VGA – an FPGA-based adapter that converts the QL video signal into modern VGA. This finally allows the QL to be used with a modern monitor without any tinkering.
• QL Power Converter – a small but extremely useful adapter board that connects a modern standard power supply to the QL's completely non-standard, rectangular power port. Anyone still using an original power supply knows exactly why this item is a sound investment.
• QIMSI / QIMSI Gold – the scene's newest project, emerging out of nowhere in the autumn of 2023 and, once again, developed by Peter Graf. A modern interface that bundles several classic expansion functions onto a single compact circuit board.

Current Points of Contact

Nowadays, original accessories can be found almost exclusively through SellMyRetro in the UK. Those wishing to avoid the hassle of UK shipping and customs can find what they are looking for at the German Sintech-Shop, which also carries QL hardware in its inventory. However, the central international hub for all things QL is the discussion forum The QL Forum—it is where developers, collectors, and users exchange ideas, where new hardware projects are first announced, and where you can always find someone with tips for tricky repairs. For those who wish to experience a QL without the risks associated with aging original hardware, the Q68 offers a sophisticated, modern FPGA-based alternative—one that I have also added to my own collection.