QDOS and compatible systems

The QDOS is the Sinclair QL operating system (QDOS = Ql Disk Operating System, nothing to do with the "Quick and Dirty Operating System" !). Its main characteristics are:

• True preemptive multi-tasking (the programs running in memory are called "jobs").
• No use of any semaphore for shared ressources access. The critical ressources (hardware/shared data structures) are accessed through "atomic" (i.e. not interruptible by another job) system calls. This guarantees that the system cannot suffer from "deadlocks", the main flaw of most (if not all) other multitasking systems.
• Dynamic memory allocation to the jobs, no inter-job memory protection mecanism (very flexible but very dangerous too...).
• "Channels" oriented inputs/outputs (the jobs access to the peripherals they need through channels). This allows to access peripherals with peripheral independant system calls (for instance "PRINT" and "INPUT" may be used with all the QL peripherals).
• All the directory device drivers (mass storage device drivers) benefit from the free memory as a cache (no disk cache software needed and the cache is dynamically allocated).
• 100% 68000 assembly written OS (it uses only 48Kb of ROM, BASIC interpreter included !) thus very fast.
• The command interpreter is the "SuperBASIC", a structured (Pascal like) BASIC. This is much more flexible and powerful than any classical shell.
• Very little memory demanding OS; the basic QL only got 128 Kb of RAM and only 85 Kb were actually available for the jobs (32 Kb of RAM being used by the screen memory)...
• High expandability (adding new device drivers to QDOS and new SuperBASIC extensions is actually very easy).
• QDOS is a "Plug'n Play" OS. The add-ons cards may have their own ROM which contents (device driver, SuperBASIC extensions) is automatically linked into the system at startup. The ROM address may also be automatically attributed.

Among the different QDOS ROM versions (FB, PM, AH, JM, JS, MG), only JS (which equiped English QLs) and MG (which equiped QLs sold in non-English speaking countries) are still in use nowadays, albeit there could still be some antediluvian QLs with a JM or even an AH ROM around...

Because of the very limited ROM space, some useful system management extensions were missing from SuperBASIC. The Toolkit II (either held in a ROM cartridge, in an extension file to be loaded in RAM or in some add-ons on board ROMs) fills these gaps.

As you can see Micro$oft did not invent anything and a "plug and play 32 bits preemptive multitasking operating system for personal computers" was already available 11 years before Windoze 95; the previous Windoze versions were using the 16 bits addressing mode of the x86 (which is much less efficient than the 32 bits addressing mode of the 680x0 or 486/Pentium), and were not preemptive (but cooperative: i.e. the responsability of the task switching initiative is left to the application instead of the OS: many crashes guaranteed !).

ARGOS is nothing else than a QDOS adaptation for Thor computers: some device drivers re-written, some new device drivers added (for floppy and hard disk especially), new SuperBASIC (renamed ThorBASIC) instructions added.

Minerva was the first true major re-write of QDOS (author: Laurence Reeves). This is an EPROM replacing the original QL ROMs. Many improvements were made to SuperBASIC (it is for instance possible to multitask several BASIC programs) as well as to QDOS.

The Minerva ROM was sold by TF Services. It is now freeware. It's last version was v1.98.

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This was initially an adaptation of QDOS for use as a QL emulator for Amiga. It was further adapted in order to run on the Q40/Q60 and to exploit all the new caracteristics of these cards (high res. graphic, sampled sound, hard disk,...). This is a freeware available for downloading and maintained by Mark J. Swift and it includes the HD driver of Qubide v1.56 (by Phil Borman).

SMS2 is a derivative from QDOS running on Atari computers in monochrome mode (640x400). It does not have any BASIC interpreter. "SMS" should stand for Small Multitasking System or Small Machine System.

SMSQ is a full re-write of QDOS by its original conceptor: Tony Tebby. SMSQ was developped from SMS2 for the Miracle systems' QXL card. It is 99% compatible with QDOS (thus the "Q" in SMSQ) while bringing many improvements (faster scheduler, higher I/O interrupts responsiveness). The SuperBASIC, that was not written by Tony Tebby, is replaced with the SBASIC, a multitasking (many SBASIC programs can run as independant jobs) "interpreter" (almost as fast as compiled SuperBASIC !). The Toolkit II extensions are built-in SMSQ as well.

SMSQ/E is born from the fusion of SMSQ and of the level "E" (thus the name) device drivers first developped for the Atari QL emulator sold by Jochen Merz Software. SMSQ/E gets the pointer environment, the window manager, the "thing" system and the hotkey system 2 (which are only extensions to QDOS/Minerva/SMSQ) built-in. The philosophy is no more to get a 100% QDOS compatible system but rather to develop new concepts. SMSQ/E runs at the moment on ATARI, (Super) Gold Card, PC thanks to the QXL and QPC/QPC2, and on the Q40 (on the Q60 as well with a patch): this is the first multi-plateform QDOS derivated OS.

SMSQ/E is now Open Source and still being developped by various contributors.