Amiga: Questions and answers - What operating systems are on the Amiga? What is "Multitasking" like on the Amiga?

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║  Amiga: Questions and answers.  ║
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 (C)WIZARD/FLASH                          
                                          
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 What operating systems are on the Amiga?   
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 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.                  
                                          
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 What is "Multitasking" on the Amiga?     
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 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.