Re: Multithreading OS for the C64

[fachat@physik.tu-chemnitz.de (Andre Fachat)]

Martijn van Buul (martijnb@stack.urc.tue.nl) wrote:
: sokos mark (msokos1@umbc.edu) wrote:
: | In article <Dtvnp8.9p3@inter.NL.net>,
: | Maarten Ruigrok <M.Ruigrok@inter.nl.net> wrote:

: | I'm guessing he uses the timer interrupt. Am I close?
: Well, I guess he is ;) I'm currently making a task-swapper myself (just
: for the fun of it. I've got no intentions or whatever blahblah), and I'm
: using the NMI for it... Those CIA's might come in hand, every now and then..

Well, I'm using the timer interrupt. But then I use the IRQ timer.
A disadvantage is, that 'nasty' programs can take full control over
the machine. An advantage is that the system itself cannot be 
interrupted when doing critical routines. Well, that could have been
taken care of with a flag (to immediately return from NMI) but
I thought it was easier this way.

And as I wanted to run close-to-hardware processes on the machine, I
wanted a process to be able to protect itself from task switching.
Which is obviously easier when just doing a SEI instead of 
calling some StopMultiTasking or RestartMultiTasking (as the Amiga does)
to access some kernel internal flag - which is not available in the 
process memory.
 
Andre

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