╔--------------═══════════---------------╗ ║ Amiga: Questions and answers. ║ ╚--------------═══════════---------------╝ (C)WIZARD/FLASH ========================================================= What operating systems are on the Amiga? ========================================================= In addition to the kernel “hardwired” into ROM AmigaOS, yes Amix (UNIX System V), NetBSD, Linux, Minix, OS/9, etc... OS/9 - very “advanced” multi-user operating system. She is bright representative of the real-time OS, but its cost is quite high - The Amiga version costs about 600 USD and Quite greedy for equipment. Amix - this is the Commodore it produced licensed version UNIX System V, there were even special UNIX Amigas A30OOUX, already supplied with UNIX. Quite a lot of Amiga servers in The Internet is not running on AmigaOS, but on NetBSD. On the other hand, unlike RS - AmigaOSis a standard de facto, and competition between different operating systems are missing. Each system is used for its own needs. ========================================================= What is "Multitasking" on the Amiga? ========================================================= In AmigaOS implemented preemptive priority multitasking. Each the task can be in three states: waiting, readiness for execution and fulfillment (obviously, in third state on a single processor the car at a given time may there is only one task). The task moving from a waiting state to readiness state, placed inqueue for execution, which is sorted by priorities of tasks, that is, having the most the task will receive high priority control of the first. The task is in execution state, maybe is derived from it in three cases: if she "voluntarily" entered into a state waiting, if from waiting state a task with high priority came out, and if the running task has exceeded the time slice allocated to it. In the last In this case, control is transferred to the task with equal priority, located in execution queues. Custom tasks usually have zero priority, and in case of their simultaneous operation they are executed in parallel. System tasks serving external devices have higher priority, and due to very low overhead costs for context switching they receive control during external events in real time. Thanks to the package Executive in AmigaOS is implemented dynamic prioritization tasks. This allows you to divide tasks into interactive and computational. The first - this is usually the I/O service: device drivers,communication programs, text editors, etc., then there are tasks that spend the most waiting time and almost no consume processor power. Second - all main working time is used full processor power: this archivers, rendering packages, etc. Executive “monitors” costs time of each task and once per second concludes which task is which set priority. As a result of this priority of interactive tasks rises and they work without "braking" associated with parallel performing computational tasks. There is a misconception that this will lead to "slowdown" of computing tasks, but using the simplest example - padding 1 kilobyte text in text editor - you can make sure that this is not like this: regardless of editor priority for the same number of actions there will be the same amount of time is spent, and the computational task will work with the same efficiency. A the editor will have higher priority work under heavy load conditions The processor is noticeably faster.
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