memory-segmentation Questions

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In 8086 assembly programming, we can only load a data into a segment register by, first loading it into a general purpose register (or memory) and then we have to move it from there to the segment ...
Positron asked 29/9, 2013 at 5:13

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I need to modify some dll, but i don't know, what excatly does segment registers (DS, SS, ...) in protected mode. I learned in school about real 16-bit mode, where segment registers multiply by 16 ...
Canner asked 11/3, 2013 at 9:27

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I was studying combined paging/segmentation systems and in my book there were two approaches to this : 1.paged segmentation 2.segmented paging I could not make out the difference between the two...

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I am reading about memory addressing. I read about segment offset and then about descriptor offset. I know how to calculate the exact addresses in real mode. All this is OK, but I am unable to unde...
Wreck asked 7/11, 2010 at 20:20

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Ever since I started with 8086 Assembly Language programming, I have been hammering my mind about these Segments and Segment registers. The problem I am facing is that I can't have a visual image o...

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I read this article: http://static.patater.com/gbaguy/day3pc.htm It includes the sentence DON'T EVER CHANGE CS!! But what exactly would happen if you did modify the CS segment register? Why i...
Ackerman asked 4/9, 2012 at 12:41

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I am studying computer architecture from the Intel Manual. The thing that I understand is that the instructions that we give are logical addresses which consist of a segment selector and an offset....
Jost asked 9/8, 2016 at 6:17

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Why did Intel choose to split the base and limit of a segment into different parts in the segment descriptor rather than using contiguous bits? See figure 5-3 of http://css.csail.mit.edu/6.858/201...
Parts asked 15/5, 2015 at 7:14

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Reading intel x86 Manual and other sources, i did not understand the difference between DPL (Descriptor privilege level) and RPL (Requested privilege level). Why is there necessity to have both? Th...
Chilung asked 14/4, 2016 at 8:34

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Most OSes use paging for virtual memory. Why is this? Why not use segmentation? Is it just because of a hardware issue? Is one better than the other in certain cases? Basically, if you had to choos...

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I'm trying to understand some specifics about about the intel x86 architecture. I have not yet really understood the call gate mecanism, but without it, for accessing a non conformant code segment ...
Ioneionesco asked 26/6, 2015 at 13:47

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I am reading about the architecture of intel's 8086 and can't figure out the following things about segmentation: I know that segment registers point to segments respectively and contain the base a...
Tichonn asked 22/4, 2015 at 1:11

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i was trying quite a while to learn what the segment registers purpose is? I All ready know that this comes from the past (8086) where there was only 1 MByte of physical memory. But the CPU's had ...
Fairlead asked 11/11, 2014 at 12:44

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If a 32bit Operating System operated with a segmented memory model would their still be a 4GB limit? I was reading the Intel Pentium Processor Family Developer's Manual and it states that with a S...

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I was reading about memory architecture and I got a bit confused with the paging and segmentation. I read that modern OS systems use only paging to manage memory access but looking at a disassemble...
Androsphinx asked 23/6, 2014 at 3:41

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In this assembly instruction mov ax, es:[bx] what does the : do?
Triangular asked 2/11, 2013 at 5:40

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I'm a beginner level of student :) I'm studying about intel architecture, and I'm studying a memory management such as a segmentation and paging. I'm reading Intel's manual and it's pretty nice to ...
Agamogenesis asked 16/1, 2014 at 15:17

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So, I know that Linux uses four default segments for an x86 processor (kernel code, kernel data, user code, user data), but they all have the same base and limit (0x00000000 and 0xfffff), meaning e...
Variance asked 1/1, 2011 at 18:1

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x86 CPUs have had all kinds of tricky modes and memory segmentation over the generations from 16-bit to 32-bit to 64-bit. These days with modern OSes using modern CPUs in modern operating modes yo...
Kebab asked 17/3, 2014 at 2:47

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Say there are many programs running at the same time. Does each executable program that runs has its own code, data, and stack segment in RAM or is the complete RAM divided into 4 segments and each...
Juristic asked 30/7, 2013 at 13:37

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I tried to figure out the details of MACRO current in Linux kernel. The final assembly code of current is: movq %%gs:0xb000,%0 The code above can work! But when I print the %%gs, its value is 0,...
Amedeo asked 16/7, 2012 at 2:44

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I am trying to understand how memory management goes on low level and have a couple of questions. 1) A book about assembly language by by Kip R. Irvine says that in the real mode first three segme...
Appaloosa asked 5/6, 2012 at 19:40

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I noticed that in Assembly segments are used in opcodes. Example: MOV DWORD PTR SS:[EBP-30],30 I think that "PTR SS:" is used to specify that EBP-30 comes from the stack? (SS: stack segment) Am...
Erastus asked 30/5, 2012 at 16:59

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After quite a bit of googling and some hints given here, I finally managed to find a layout of the FS segment (used by windows to store TIB data). Of particular interest to me is the ArbitraryUserP...
Tetchy asked 13/2, 2012 at 13:34

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I'm teaching my 12 y.o. 8086 assembly language and yesterday we were talking memory, addressing and segmentation. I showed him how segments can be visualized as a sequence of overlapping 64Kb block...
Qadi asked 4/1, 2012 at 14:8

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