questions about real mode and protected mode

[chendsh]

Hello,
I have 2 questions about real mode and protected mode, I hope there
will be some advice from you, thanks in advance.

1.I dont know the point from which the program is in Unreal mode.
Only after I am in fully protected mode and make a jump to Real mode?
I saw a progam just changes into Partial protected mode by setting CR0
and GDT, and then sets CR0 to Real mode . Is this mode the Unreal mode?

2.When should I set segment registers for Protected mode , before the Far
JMP or after it?

[Guest]

>On 2002-04-18 22:12:20, chendsh wrote:
>1.I dont know the point from which the program is in Unreal mode.

unreal mode:
1. set PE bit in register CR0
2. load any or all of DS/ES/FS/GS (not CS/SS)
3. clear PE bit in register CR0

full protected mode:
1. set PE bit in register CR0
2. load ALL segment registers (including CS)