I would like to lern how to switch between protected and real modes.
I have a lot of tutorials so I needn't more of them but, it is not so easy to do it under w2k.
Which freeware systems are suitable?
What system should I install?
Posted on 2003-09-04 15:59:06 by etn
An application running under a protected mode operating system at privilege level 3 can't switch to real mode. If you need to call real mode code, it must be run in V86 mode. Look at the Windows 2000 DDK documentation for details on how to do that.
Posted on 2003-09-04 16:50:51 by Sephiroth3
I have been thinking about increasing my skills and ability. I don't want run enything beside switching modes.I Just want to know how.Maybe this exercise comes in useful to build my own minisystem.

with regard to V86 ,the mode is unuseful because like in pmode you can't use out ,in or int op-codes which are privilige for the sysem kernel and most programs do not work.

any:alright: ideas?
Posted on 2003-09-05 01:38:06 by etn
There is an OS Construction forum here,

Besides you can check SolarOS (my os) source code and or other ASM OSes like: MenuetOS or V2OS and many others you can find on Google. You can also ask me questions.

Switching to pmode (from boot) is neither advanced programming nor easy, just a set of sucessive operations that must be done ... basically:

-enable A20
-load GDT and eventually IDT with valid pointers to system descripor tables
-set PM bit in CR0 register
-jump to clear CPU instruction cache
-Jump far to your code_selector:mini_os_entry_point
-reprogram PIC controller IF you have enabled/loaded IDT above

that is it .

Understanding why you must do such things might breing some expertise into your CV but it is not such a big fuzz as everybody expects
Posted on 2003-09-05 02:39:01 by BogdanOntanu

There is an OS Construction forum here,

havent seen this yet?
where is this exactly ??????
Posted on 2003-09-05 04:05:55 by Ranma_at
A subforum under Heap.
Posted on 2003-09-05 04:24:40 by roticv