On 27-3-2013 12:14, Orchid Win7 v1 wrote:

>>>> At the user level it was not fully preemptive. You had to do an
>>>> explicit
>>>> call to allow other programs to get some time too.
>>>
>>> What in the world makes you think that?
>>
>> Because I have written programs at that level.
>> It is a great way to avoid a busy wait on an event in a high level
>> language. Just check if your condition is met, if not pass control back
>> to the scheduler. Repeat until you have something to do.
>>
>> What I remember from those days is that a process could be interrupted
>> by a higher level process, but user programs ran until they voluntary
>> gave control back to the scheduler.*
>
>> *) trying to google things, the wiki page on Exec_(Amiga) claims that
>> linus once mistakingly said that AmigaOS was cooperative. In earlier
>> versions of this page it *was* apparently considered cooperative,
>> because google quotes a text that is no longer there.
>
> http://en.wikipedia.org/wiki/Exec_%28Amiga%29
>
> "Exec is the multi-tasking kernel of AmigaOS. It enabled pre-emptive
> multitasking in as little as 256k of memory (as supplied with the first
> Amiga 1000s). Exec provided functionality for multi-tasking, memory
> allocation, interrupt handling and handling of dynamic shared libraries."
>
> Sounds pre-emptive to me...

Either you did not understand what I wrote or you are from the younger 
generation that thinks just one source is enough. (a slightly belated 
happy birthday from me anyways)
I said that there are two positions to be found
1) that it *used to be* a cooperative multitasking system
2) that it *is* a pre-emptive multitasking system
You can count on it that I have seen that wiki-page. From that you can 
simply deduce that this did not settle the discussion for me. So quoting 
it as the definitive source that it has *always* been a pre-emptive 
system is a bit silly.


-- 
Women are the canaries of science. When they are underrepresented
it is a strong indication that non-scientific factors play a role
and the concentration of incorruptible scientists is also too low

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