[Coco] [Color Computer] You can lean on me - New Electronics reference article on OS-9

[Neil Morrison]

http://www.newelectronics.co.uk/article/index.aspx?articleid=wQMUXhExH7EaLrFZ8j_HFML5LERApvMKlJrSLCjsvPUA

You can lean on me 09/10/2006   Rooted in the early 1980s – specifically, the Tandy Colour Computer 3 – the OS-9 operating system is proving to be something of a comeback kid. With a large installed base, it continues to gain design wins today. So why is something that was originally developed as a platform on which to run a basic language interpreter more than 20 years ago, continuing to gain followers? 

Ric Yeates, senior software architect on RadiSys’ OS-9 project, attributes OS-9’s popularity to several factors. Firstly he suggests: “It was used to support the Motorola 6809 processor (which featured in the popular Tandy computer) and it was a logical progression to convert this run time environment to a full OS. So that’s where it got its size and performance characteristics.” 

Although the 6809 was a 2MHz processor, OS-9 enabled it to scale to work with one user or tens of users – as developer Microware did internally. Recounts Yeates: “Customers were using OS-9 in one embedded system out in the field. However, we were using it in house to run our development and sales/marketing operations. 

Unlike previous OS’, we didn’t have to reboot OS-9 several times a day.” OS-9 can be scaled from a completely diskless environment without I/O, to a full system supporting serial, disk, internet and more, unlike Unix’ structure, which had provided inspiration for OS-9’s developers. 

Its real time, multiuser, multitasking characteristics are down to the modular architecture to which OS-9 subscribes, according to Yeates. New devices can be added to an OS-9 system simply by writing device drivers, with I/O devices treated as files. Applications and drivers can be dynamically loaded and unloaded during development or after deployment without a reboot.