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Four registers are used to refer to four segments on the 16-bit x86 segmented memory architecture. DS (data segment), CS (code segment), SS (stack segment), and ES (extra segment). Another 16-bit register can act as an offset into a given segment, and so a logical address on this platform is written segment:offset, typically in hexadecimal ...
Some systems have a "split" memory architecture where machine code, constants, and data are in different locations, and may have different address sizes. For example, PIC18 microcontrollers have a 21-bit program counter to address machine code and constants in Flash memory, and 12-bit address registers to address data in SRAM.
Start monitoring a memory location for memory writes. The memory address to monitor is given by DS:AX/EAX/RAX. [m] ECX and EDX are reserved for extra extension and hint flags, respectively. [n] Usually 0 [o] Prescott, Yonah, Bonnell, K10, Nano: MWAIT [l] MWAIT EAX,ECX: NP 0F 01 C9: Wait for a write to a monitored memory location previously ...
In the original 8086 / 8088 / 80186 / 80188 every address was built from a segment register and one of the general purpose registers. For example ds:si is the notation for an address formed as [16 * ds + si] to allow 20-bit addressing rather than 16 bits, although this changed in later processors.
The x86 architecture in real and virtual 8086 mode uses a process known as segmentation to address memory, not the flat memory model used in many other environments. Segmentation involves composing a memory address from two parts, a segment and an offset ; the segment points to the beginning of a 64 KiB (64×2 10 ) group of addresses and the ...
first x86 processor with protected mode including segmentation based virtual memory management. Performance improved by a factor of 3 to 4 over 8086. Included instructions relating to protected mode. The 80286 had a 24-bit address bus.
For example, in the tiny model CS=DS=SS, that is the program's code, data, and stack are all contained within a single 64 KB segment. In the small memory model DS=SS, so both data and stack reside in the same segment; CS points to a different code segment of up to 64 KB.
The 8086 [3] (also called iAPX 86) [4] is a 16-bit microprocessor chip designed by Intel between early 1976 [citation needed] and June 8, 1978, when it was released. [5] The Intel 8088, released July 1, 1979, [6] is a slightly modified chip with an external 8-bit data bus (allowing the use of cheaper and fewer supporting ICs), [note 1] and is notable as the processor used in the original IBM ...