What is the role of segment register?
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Answer / manoj saini
In the x86 processor architecture, memory addresses are
specified in two parts called the segment and the offset.
One usually thinks of the segment as specifying the
beginning of a block of memory allocated by the system and
the offset as an index into it. Segment values are stored
in the segment registers. There are four or more segment
registers: CS contains the segment of the current
instruction (IP is the offset), SS contains the stack
segment (SP is the offset), DS is the segment used by
default for most data operations, ES (and, in more recent
processors, FS and GS) is an extra segment register. Most
memory operations accept a segment override prefix that
allows use of a segment register other than the default
one.
| Is This Answer Correct ? | 18 Yes | 6 No |
Answer / shabir gojree lpu, jalandhar
The segment register in the 80806/8088 microprocessor
contains the base address (divided by 16) of a region of
memory. Since the register is 16 bits in size, there are
65,536 possible segment base addresses, ranging from 00000H
to FFFF0H, in increments of 00010H.
After address translation at the instruction level, the
generated 16 bit offset is added to the selected segment
register times 16 to generate a physical address between
00000H and FFFFFH. (If the offset and base go past FFFFFH,
they wrap around back to 00000H.) Since the offset is also
16 bits in size, and since the overlap is only 4 bits
(times 16), then each 64 kb segment overlaps by 16 bytes.
There are four segment registers; CS, DS, ES, and SS,
standing for Code Segment, Data Segment, Extra Segment, and
Stack Segment.
CS is used for opcode fetches. DS is used for normal data.
ES is used for certain string operations as the destination
address. SS is used for stack and frame (BP) data.
The segment registers can be implicitly selected by
context, or they can be explicitly selected with a segment
prefix opcode.
| Is This Answer Correct ? | 8 Yes | 3 No |
Answer / nand kumar jyotish
basically registers are used to store data and address. for
specifying the base address i.e starting block of
memory ,segment registers are used . it gives only the
starting adress of any segment .one thing is important in
the case of 8086 architechture is that ,for producing
physical address ,the segment register address must be
rotate bit-wise 4 times left and 0000 must be embedded. now
offset address is added in the modify content of segment
register to get the required memory location.
| Is This Answer Correct ? | 6 Yes | 3 No |
Answer / debasish mishra
'normal' address space in 8086 is 16 bit r which allows it to address 64k of linear memory space. Using segment registers to select a 'bank of memory' the cpu can use much more (20 bit addressing space)
| Is This Answer Correct ? | 2 Yes | 1 No |
Answer / shabir gojree lpu
In the x86 processor architecture, memory addresses are
specified in two parts called the segment and the offset.
One usually thinks of the segment as specifying the
beginning of a block of memory allocated by the system and
the offset as an index into it. Segment values are stored
in the segment registers. There are four or more segment
registers: CS contains the segment of the current
instruction (IP is the offset), SS contains the stack
segment (SP is the offset), DS is the segment used by
default for most data operations, ES (and, in more recent
processors, FS and GS) is an extra segment register. Most
memory operations accept a segment override prefix that
allows use of a segment register other than the default
one.
| Is This Answer Correct ? | 5 Yes | 6 No |
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