X86 Protected Mode: Advantages, Process Protection & Memory Protection

[Stephanus]

Dear PF Forum,
What does "Protected mode" means in x86 architecture?
I try to understand this, but failed.
This is the "Protected Mode" advantages from http://prodebug.sourceforge.net/pmtut.html#Advantages that I read:
- Access to 4 gigabytes of memory
- Virtual memory
- Address translation
- Programs work with logical addresses.
- Improved segmentation
- Memory protection <-
- Process protection <-
- 32-bit registers
- Improved addressing modes
- Multitasking support
- Hardware debugging
All these have nothing to do with the word "Protection" only in this two section:
- Memory protection <-
- Process protection <-

So what I really want to know is this:
- Process protection

In a similar fashion to memory protection, different programs (or parts of a program) can be protected from each other. One program might not have access to another program's data, while the operating system might have access to everyone's data. Conversely, user programs may have only limited access to the operating system's data. This is actually implemented using the page protection mechanism provided by the MMU.

Supposed my program is allocated at 10000h to 20000h
so when I try to
mov AX,[20001h]
1. does the processor really send something? Perhaps interrupt?
2. Is there really one or two instructions before the OS JMP to my program, that the next instruction will be limited to access 10000h to 20000h?
Thank you very much

 

[Mark44]

See https://en.wikipedia.org/wiki/Protected_mode and https://en.wikipedia.org/wiki/Protection_ring

 

[Stephanus]

See https://en.wikipedia.org/wiki/Protected_mode and https://en.wikipedia.org/wiki/Protection_ring

Thanks @Mark44 for your answer.
While https://en.wikipedia.org/wiki/Protection_ring only address "vertical" protection, I mean. a program with lower privileged level/high privilege number can only access instruction in a predefined manner, I want to know what about the "horizontal" protection (but I learn something new, too. Protection Ring). Can a program access memory that's not allocated to it? The answer is no. But how the processor handle this? Does the processor really thrrows an exception?
https://en.wikipedia.org/wiki/Protected_mode#The_286 addresses similar issue.

Virtual 8086 mode
With the release of the 386, protected mode offers what the Intel manuals call virtual 8086 mode...

Virtual 8086 mode, however, is not completely backwards compatible with all programs. Programs that require segment manipulation, privileged instructions, direct hardware access, or use self-modifying code will generate an exception that must be served by the operating system...

So, the processor does throw exception. But it's in Virtual 8086 mode. What about in protected mode? Will the processor generate an exeption if a program is trying to access memory parts that's not allocated to it?
Thank you very much.

 

[Stephanus]

Ahh, I've found it here
https://en.wikipedia.org/wiki/General_protection_fault
Thank you very much for the effort though