Operating Systems on the Atari ST and compatibles

The Atari ST really was/is the Janus of computers, on the one hand, with it's high resolution monitor, it was an Apple Mac clone, and GEM was so like the Classic Mac OS interface it is quite staggering. Technically the ST put the Mac to shame, running faster, having higher resolutions and having a better monitor. TOS/ GEM wasn't quite as user friendly, but was also less bound by convention, which was both a blessing and a curse. On the other hand, with a colour monitor, high colour graphics and a blitter, the ST was also a killer games machine, not too far behind its other main competitor, the Commodore Amiga. Then there is the IBM compatibilty of the ST, which comes from GEM's CPM/ DOS roots. The ST truly was a Jack (Tramiel?) of All Trades. Times change however and Atari's slow updating of the GEM/ TOS environment led to the development of multiple alternative operating systems for the ST. These are discussed, along with their suitability for various hardware in this guide.

Let's start at the beginning...

TOS (The Operating System)/ GEM (Graphic Enviroment Manager)

TOS 1.00 - 1985 to 1987

In the beginning there was nothing but darkness, and then into this darkness came Atari's TOS 1.00! TOS 1.00 was initially released partly on internal ROM (Read Only Memory) and partly (because it wasn't finished at the time of the ST's speedy development) on floppy disk. Quickly TOS was moved entirely onto ROM. It was an interesting and brave choice by Atari. Putting the operating system on ROM, meant it became virtually bullet proof to the disk corruption that would plague Mac, PC and Amiga operating systems. No matter what happened with your software, you could have a warm cosy feeling knowing that, as long as the hardware was working, so would your operating system. It also meant it was superfast at loading, the desktop appearing on screen almost as fast as the text based operating systems of the 8bit era. TOS/ GEM, it should be noted, was the first colour graphical user interface on any computer. On the minus side it meant that bugs were more difficult to quash than those of disk based operating systems, and updates were fewer (although if you compare the evolution of the Amiga and ST operating systems when they were in development it is hard to see a greater level of Amiga releases).

The operating system was simple in one sense, in that it was mainly a single tasking environment where you could not run more than one main program at once. However this isn't strictly true. While Amiga owners (quite rightly) shout from the roof tops about their multi-tasking OS, it is less well known that the ST is also multitasking. Well sort of. The ST can run up to seven programs at once, one main program, and six desk accessories (I suppose technically it can run more, in the form of TSR (Terminate Stay Resident) programs, but the user cannot really interact with these). The desk accessories are part of a very basic, so-called, co-operative, multitasking system.

TOS 1.00 had some serious problems. No hard disk had been developed for the ST by the time of its release, and consequently its reliability with hard drives is not great. One major bug was the limit of hard drive partitions to 16mb, a serious problem even then.. It also suffered from slow floppy access and no support for the, also unfinished at the time of the ST's release, blitter chip. While we are on the subject of incomplete parts of the operating system, we should also mention GDOS (Graphics Device Operating System). GDOS was meant to have been in the operating system from the start, but due to the memory limits of the basic ST (512kb) and some development problems, did not make it onto the ROM and was instead included as an auto folder program. The Auto Folder and GDOS and its replacements are too complex to go into this article and will eventually get tutorials for themselves. Needless to say the GDOS situation was a travesty, and one of the reasons the Mac prevaled against its more powerful young upstart competitor. Other problems involved buggy serial port code and what eventually became known as the 40 folder bug. This annoying bug would be the bane of hard drive users, and relates to a limit of a maximum of 40 folders being opened in one session. Not a problem usually with a floppy, but on a hard disk... A patch was issued, but this was one bug (also along with the serial port bugs) that survived on right into the Falcon era.

TOS 1.02/ 1.2/ 1.09 - 1987 to 1989

Consequently TOS 1.00 was replaced, although it is quite a common OS, having appeared in all the early STs, the STF and some very early STFMs. The advent of the Mega ST, the STFM and the release of the blitter chip heralded the first major OS revision. TOS 1.02 or 1.2 (or confusingly 1.09). The new OS fixed most of the problems with hard disks (bumping up the partition limit to 32mb (though this can be easily expanded)), quashed quite a few bugs and added support for that under-used little wonder, the blitter chip. TOS 1.02 is probably the second most common OS variant out there. It was however still flawed in some respects. Disk access to both hard drives and floppies were still slow. A patch, in the form of Codehead's 'Pinhead' auto program, fixed a lot of these problems and this was eventually incorporated into TOS 1.02's successor. TOS 1.02 could also not rename folders and its file selector was still the pretty dire one from TOS 1.00. There were also no keyboard short-cuts.

TOS 1.04/ 1.4 - 1989 - c. 1992

As the STFM started to grow a little long in the tooth, and as its successor the STe loomed on the horizon, Atari released the final ST/STM/STF/STFM specific version of TOS, 1.04. This finally fixed the slow disk access problems, bug-fixed the serial and Folder 40 problems (but in such a way as they were never properly fixed) and improved overal system reliability. Keyboard shortcuts were added for 'soft' and 'hard' resets and the file selector had a welcome facelift. Most changes though were under the hood and there was no change to GEM's overall look. TOS 1.04 is probably the most common Atari ST OS out there, mainly due to the popularity of the STFM model, which even outlived it's successor, the STE.

Multidesk (Codehead Software)

Multidesk was a sort of Atari equivalent of the Mac's Multifinder, accept it was not an official Atari release. It was a seminal program in a way, but not quite the full multitasking system that ST owners deserved. Multidesk basically allowed you to overcome the six program limit for desk accessories, and allowed you to unload them and reload them at will. Handy, and step in the right direction, but not quite the jackpot. A similar program, called Chameleon, was also capable of this very limited multitasking.

Back in TOS land.. TOS 1.6 and 1.62 - 1989 to c. 1992

The release of the STe heralded a new OS version, though again the improvements were all under the hood. TOS 1.6/1.62 was basically TOS 1.04, but with support for the STe's new hardware. TOS 1.6 shot itself in the foot with a few dodgy bugs, including a ridiculous one that stopped it booting in medium resolution, and was swiftly replaced by the final STe specific TOS version, 1.62.

TOS 3.01/ 3.06 - 1990 to 1993

The release of the Atari TT 32bit computer in 1990 heralded the first major OS update in several years. TOS 3.0 not only was enhanced to handle the TT's powerful new hardware, but also gave tired GEM an good lick of paint. Keyboard shortcuts for most menu functions were added. Support for larget hard disk sizes and partitions was added and HD floppy disk support was incorporated. Support for IDE hard disks and memory beyond the 4mb GEM limit (known as 'Fast Ram') was added. Programs could now be dragged to the desktop, and files could be assigned from a range of different icons. The icons were still predominently black and white, but by this point there were rumbles from developers in America and Europe and things were about to change..

Hold on, what happened to TOS 2? Or TOS 2.06.. 1990 - 1993

Well spotted. TOS 2.06 was basically TT TOS/GEM for the earlier Atari models, but specifically released with Mega STe. All Atari owners (with the exception of TT owners of course) could now update to this operating system, although owners of the STFM and earlier models required an adaptor in order to use it. For the STE is was just a straight ROM swap. TOS 2 was released at approximately the same time frame as TOS 3 and they are both based on the same code.

TOS 2.06

Alternative Desktops.. - 1990 onwards

The GEM desktop was never more than functional in its early days and by the very late eighties/ early nineties, alternative desktops emerged to replace the standard desktop offering. The most notable early pioneers were Neodesk (N-America), Gemini (Germany) and Kaosdesk (Germany), the former and latter of which would go onto big things. Kaosdesk formed part of a suite called KaosTOS, which could be burnt like TOS to ROM chips. KaosTOS fixed a lot of TOS/GEM bugs and was written entirely in assembly rather than a mixture of the former and the C language. All the desktop replacements mentioned improved functionality, but often picking which one was a entirely personal thing. Well diversity was nice, they also tended to offer different features, which led to further fragmentation in the operating system. Another desktop worth mentioning at this point is Teradesk, a simple free desktop that would later become the ST world's first open source desktop.


TOS 4.01, 4.02 and 4.04 - 1992 to 1993

With the Falcon came a new version of TOS/GEM, version 4. The enhancements are mainly relating to aesthetics, with GEM finally getting a full colour make-over. Full colour (well 256 colour) icons could be used desktop and in windows, although these were loaded from disk rather than being present in ROM. The windows also gained a '3D' look similar to that found in Windows 95. At the time these visual enhancements were a big thing, but they don't seem to have aged as well as the classic GEM look. The other main enhancements revolved around support for the Falcon's enhanced hardware, with support for extended resolutions, colours and sound hardware. The first two versions were buggy and it was advisable to upgrade as soon as possible if your Falcon contained them. Annoyingly TOS 4 still contained the folder bug, the serial port bugs and introduced a couple

MINT (Mint Is Not TOS)

While TOS development chugged along, a software programmer called Eric Smith had been working away on a UNIX style operating system for the ST. Atari got wind of this, as they had flirted with UNIX occasionally in the past (the TT was meant to have its own version), they hired Eric and worked with him to develop...

MULTITOS - 1992 - 1993

Finally Atari released a full on multitasking system for the Atari. Multitos was actually, thanks to its MINT/UNIX origins a rather powerful operating system. It consisted of two main parts, MINT (now standing for Mint Is Now TOS btw), and a fully multitasking AES (Application Environment System). On paper it looked amazing, the multitasking was pre-emptive, something the fledgling Windows and Mac OS were not (though the Amiga was), and had also sorts of goodies such as loadable extensions and filesystems. The AES was based on TOS 4.04 and was also a marked improvement on earlier releases. Apart from one thing. It was slow. Released with the Falcon, MultiTOS proved to be a slug, that reduced graphical performance of Atari's wonder machine by around 25% or more. Compatibility also suffered, especially when used with one of its features 'memory protection', switched on. On the older STs MultiTOS was so slow as to be unuseable, and the lack of proper memory protection in the old Motorola 68000 CPU prevented it from being a lot of use there anyway. Subsequently it was ignored, and despite an unreleased AES update that would have improved the speed considerably, it failed almost immediately upon the launch of first Geneva, then Magic. Atari by this point had lost interest and were focusing on the Jaguar console.

TOS 4.92 - 1993

Atari's last unreleased version of it's TOS/ GEM environment and the prototype for what would have been TOS 5, a complete intergration of MultiTOS and TOS. A bug filled alpha version slipped out and looked promising, but Atari's OS team were shifted across to write software for the Atari Jaguar's CD add-on, and the operating system TOS died.. or did it..


Within months of the release of MultiTOS, the USA developers of the Neodesk desktop replacement unleashed a bombshell. Geneva. Here was a, albeit co-operative, multitasking system that worked well, was in some cases faster that the single tasking GEM, and was not only useable on the 32bit ST compatibles, but thanks to a small memory footprint could also run quite well on a plain vanilla 1mb ST. Geneva was designed from the start to be used with Neodesk, and the two compliment each other well, although Neodesk's way of doing things isn't always to everyone's tastes. Other desktops can be used, but they don't intergrate so well. You could however also use Geneva as just a program launcher, without even running a desktop, if you were short on memory. Geneva, probably thanks to its co-operative multitasking roots was more compatible with a lot of the older ST software than probably any of its rivals were. Programs could usually be persuaded to run in one form or another, and you could even switch Geneva to single tasking mode if a program was particularly fussy. The latter versions of Geneva added support for Mint (the survivor of MultiTOS), which allowed full pre-emptive multitasking if you wanted it. For a while Geneva was top dog, and proved extremely popular, reaching version 6, however a challenger was waiting in the ranks...


Shortly after the release of Geneva, German programmers (some of whom were responsible for KaosTOS, and others linked with the screen accelerator NVDI) released Magic, or MagiX as it was initially called. Like Kaos-TOS, Magic was a complete assembly written re-write of TOS and GEM. The twist here was the fully pre-emptive multitasking OS, which ran faster than the basic TOS/ GEM OS. Magic shipped with a desktop, imaginatively called Magicdesk, which although not as fully featured as Neodesk, was a considerable improvement on the built in desktop. The environment owed quite a lot to Apple's Classic OS. Magic proved extremely popular, and with its exellent intergration with the screen accelerator/ printer driver/ font system, NVDI, proved to be the discerning Atari owners system of choice. Magic also formed the focus for a new round of desktop replacements, such as Ease, Thing and the be all and end all of desktops for the Atari, Jinnee. There were a couple of flaws with Magic though. It's compatibility with music software was never quite right, which alienated some of the STs core users. Software compatibility in general, mainly due to the pre-emptive nature of the multitasking system, never seemed as good as that with Geneva or basic TOS/GEM. Magic reached version 6, and was transported eventually to the Milan Atari clone. Unfortunately it also seemed to die a death with the ill-fated Milan 2. Development faltered, Magic fell behind and was eventually superceded by a re-emerging Mint.

Magic operating system

More Alternative Desktops

As Geneva and Magic raced for the No. 1 spot, the desktop battle heated up as well. Neodesk reached its final and ultimate form in version 4, seemingly intergrating flawlessly with Geneva, but at the expense of some other, more popular desktops. Thing, for a short while, was the most popular desktop on the market, sporting a nice interface and what everyone thought were all the bells and whistles a user could want. A version of Thing, imaginatively titled Ming, became the desktop of choice for the Milan Atari clone. Thing has recently been released as open source, and looks like it will return to the top of the desktop pile. Another desktop, Ease, was designed to intergrate seemlessly with Magic, and replace Magicdesk. For a while it seemed like the rolls royce of desktops but it was expensive, development stalled and then the monster that is Jinnee was released. Again based on a tight intergration with Magic, Jinnee was so powerful it surpassed the Apple Mac OS versions of the same time period. For a bit the Atari had the operating system the platform deserved. Eventually the decline of the ST market led to the development of Jinnee ending. Sadly the source code was lost, and Jinnee will evolve no further..

The Thing desktop in all its glory!

Clone TOS Variants

Clone makers Medusa released several Atari clones, such as the Hades, which used a specially modified version of TOS 3.06, licensed from Atari, in their machines. Little was changed in the user functionality of the OS, but obviously they were adjusted to take advantage of the new hardware. Shortly after the release of the Hades (which until the Firebee was created, was still the most powerful TOS clone). TOS 4.05, a modified version of the Falcon's 4.04, formed the base interface for the Milan computer.

MINT reborn. Also NAES, XAAES and MYAES...

Packaged along with the Milan was a MINT based multitasking OS, called, surprisingly, Milan Multi OS. The package comprised of the then current version of MINT and NAES, a re-write of Atari's abandoned Multi TOS AES. The power of the Milan should have been the ultimate showcase for the rejuvenated Mint. It never seemed to work however, the system lacked compatibility and seemed to suffer the continual curse of MINT. Magic Milan blew it away in terms of speed. NAES reached version 2, and then development ceased. MINT needed a new partner. Step forward XAES. XAES is an open source version of AES (Application Environment System) part of GEM. Specifically it is developed in tandom with Mint, so compatibility is at its highest. XAES is powerful and rugged, but lacks the aesthetic appeal of user interfaces on other platforms. MyAES on the other hand isn't open source, but the interface is much more appealing. So MINT has finally triumphed and is the last developed OS on the Atari. Support for networking via ethernet, USB and other 'modern' interfaces have been added. Unfortunately Mint still seems like it is waiting for an Atari powerful enough to handle it. Even on the CT60 system booster for the Falcon, it still feels clunky. MINT's compatibility with older Atari software is also problematic, but Mint afficionados tend to suggest that if the software doesn't work under MINT you shouldn't use it. Unfortunately on a system with limited new software development, incompatible software is a real problem. Hopefully the Firebee will be the system that MINT will finally shine on.

And finally EmuTOS and the Firebee

Slowly germinating over the course of what seems like almost a decade, the Firebee is a Coldfire based Atari clone due for imminent release. As usual TOS forms the basis for the system, although MINT seems to form the power interface for the computer. Alternatively to the altered Atari TOS the user can use EmuTOS, a slowly maturing open source version of TOS, built from the original, now open source, version of GEM for the PC. It isn't fully finished but works well enough to act as a booting system for Mint and the Atari emulator ARAnyM (Atari Running on ANY Machine).

Alien operating systems for the Atari

Along with the TOS compatible operating systems mentioned above, software companies and programmers occasionally released the odd oddity. A version of LINUX/UNIX was released late in the Falcon's lifespan and a Unix variant called Minix was released fairly early on. Two operating systems that you may not have heard of were Omen and SMS2. Both completely replaced the OS on the ST, with Omen in theory aiming to be a totally cross hardware platform independant OS. SMS2 was based on a similar principle and came on a hardware card that plugged into the cartridge port. Both were very powerful for the time but both operating systems ultimately failed due to lack of software support. They perhaps should serve as a warning to the Mint developers..


One of the draws of the ST was its rather good emulation of other computers. Namely the PC and the Mac. We will cover these in a future tutorial.


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