- #1
Stephanus
- 1,316
- 104
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
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
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
Supposed my program is allocated at 10000h to 20000hIn 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.
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