Re: 6502 Multitasking OS announce

[ralph.mason@liffe.com (Ralph Mason)]

holger@deep.hb.provi.de (Holger Bruns) wrote:


>I guess, it will not work. The tasks cannot be executed independently. Only 
>the task on top of the stack will work without causing errors. Assume the 
>parameters of task 1 have been pushed to the top of the stack. The parameters 
>of task 2 are below of them. Now you try to execute task 2. Your stack 
>register will point to the bottom of the parameters of task 1. Pushing any 
>data to the stack will overwrite the parameters of task 1. Assume your 
>system decides to execute task 1 after executing task 2. Since the parameters 
>of task 1 are corrupted in this case, the system will crash.


This method will work just fine, it just gives small stacks by
dividing the large ( can you call 256 bytes large? ) stack into
smaller stacks.  Now providing all tasks play by the rules and do not
use more than their stack allocation there is no problem.  I believe
that this is what the non MMU version of his OS does.  You still don't
have seperate zero pages though :(

-Ralph