TOS

TOS was the operating system used on the Motorola 68k based computer systems released by Atari in mid 1980's and early 1990's, the ST, Mega, TT and Falcon systems. An official explanation for the acronym was never given by Atari, but it is often said to simply mean "The Operating System", or perhaps "Tramiel Operating System", after the owner of Atari Corporation at the time, Jack Tramiel.

TOS is stored on non-rewritable ROM chips attached to the motherboard, giving the system an "instant on" capability. However, if no disk was present (either hard or floppy) the system would usually wait a considerable time before booting to chance for one to be inserted.

The TOS ROM's contain the GEM (Graphical Environment Manager) GUI from Digital Research, and is similar to the MAC-OS "classic" GUI of the mid 1980s. Early versions of this (prior to TOS 2.06) were restricted in that additional icons could not be placed on the desktop for quick launching. Later versions were much more flexible. In addition it was possible to use any number of third party "replacement" desktops (and even complete GUI's).

TOS allows for co-operative multi-tasking. This is done by the use of "Accessories", specially designed programs that are launched on startup and accessed from the "Desk" menu. They are distinguished by having an *.acc extension and must be stored in the parent or BOOT directory on a disk or hard drive. Normal (*.PRG) programs cannot be used as accessories. Up to 6 accessories may be available on any one boot partition. Only one *.PRG program may be used at once.

In the early 90's it became clear that a true multi-tasking was the future of operating systems. Although TOS had been greatly improved by a mix of incremental developments, particularly with the release of the Atari Falcon, it was also the release of this more sophisticated system that showed the limitations of the system.

An independent programmer from Canada, called Eric Smith had already been exploring such options when he realised the difficulty of porting UNIX programs over to TOS. He developed a multi-tasking operating system that was fully TOS compatible, but contained better, though still limited, multi-tasking, and several UNIX similarities, making porting programs from UNIX much simpler.

Smith had released his work on the internet as a GNU project, and a prominent programmer at Atari itself, Allan Pratt, became aware of the project, and suggested that Atari use MiNT as a kernel for a new and improved version of TOS that would be able to take advantage of multi-tasking and also improve it's networking skills. Later Atari systems had, after all, been released with both AppleTalk networking ports, and the Falcon sported as DSP port, which it was anticipated would be used for a sophisticated type of analogue modem, which ultimately never surfaced.

The proposal for MiNT forming the basis of a new version fo TOS was accepted, and MultiTOS was born.

MultiTOS was a major leap forward for TOS, and in some ways this was its downfall. The new AES, which handled graphical calls and essentially acted as the bridge between the operating system itself as the GEM desktop was a dramatic step forward from previous versions, including three dimensional and colour icon support, as well as extended colour depths and all the slightly weird screen resolutions that the Falcon supported with its entirely new VIDEL graphics chip. This, combined with the heavier MiNT kernel made the OS slow and somewhat bloated. It was the only version of TOS since v1.0 to be supplied on floppy disk (a further performance bottleneck) rather than ROM.

In addition, MultiTOS supported true multi-tasking, improving on MiNT's early restrictions of being able to support multiple command line ("TOS applications"), but not but programs that used the GUI ("GEM applications").

MultiTOS also included support for all the hardware of the Falcon that was unique to it within the range of Atari computers, such as its IDE interface (other Atari systems used SCSI and ACSI, an Atari propieatry system similar to SCSI), the DSP chip and dedicated DSP port.

The problems were far from insurmountable, and a few relatively modest hardware and software tweaks could have made the standard Falcon / MultiTOS system a usable if not spectacular combination, but Atari had since shifted their focus from computers to games consoles, and the decision was made to completely abandon support for MultiTOS and the entire computer line, and focus on the Jaguar console, leaving behind several almost completed improvements and new developments.

As Atari abandoned MultiTOS, Smith persuaded Atari to release the MultiTOS code onto the internet, to allow further community development. Atari agreed, and MultiTOS and MiNT ultimately swapped roles, MultiTOS becoming the foundations for a new generation MiNT operating system. As open source and third party development of Atari-based hardware developed, the bottlenecks imposed by the Falcon hardware were mostly overcome, and MiNT has been able to develop increasingly sophisticated features, incorporating advances from both other TOS projects as well as the Linux world.