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In real mode or V86 mode, the fundamental size of a segment is 65,536 bytes, with individual bytes being addressed using 16-bit offsets. The 16-bit segment selector in the segment register is interpreted as the most significant 16 bits of a linear 20-bit address, called a segment address, of which the remaining four least significant bits are ...
In computer architecture, 16-bit integers, memory addresses, or other data units are those that are 16 bits (2 octets) wide.Also, 16-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers, address buses, or data buses of that size. 16-bit microcomputers are microcomputers that use 16-bit microprocessors.
Will change OperandSize from 16-bit to 32-bit if CS.D=0, or from 32-bit to 16-bit if CS.D=1. 67h: AddressSize override. Will change AddressSize from 16-bit to 32-bit if CS.D=0, or from 32-bit to 16-bit if CS.D=1. The 80386 also introduced the two new segment registers FS and GS as well as the x86 control, debug and test registers.
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 ...
Otherwise it's the 16-bit max 0x0000ffff. Essentially the same meaning as "D". L=Long If set, this is a 64-bit segment (and D must be zero), and code in this segment uses the 64-bit instruction encoding. "L" cannot be set at the same time as "D" aka "B". (Bit 21 in the image) AVL=Available For software use, not used by hardware (Bit 20 in the ...
It is technically possible to use up to 256 KB of memory for code and data, with up to 64 KB for code, by setting all four segment registers once and then only using 16-bit offsets (optionally with default-segment override prefixes) to address memory, but this puts substantial restrictions on the way data can be addressed and memory operands ...
The segment address inside the descriptor table entry has a length of 24 bits so every byte of the physical memory can be defined as bound of the segment. The limit value inside the descriptor table entry has a length of 16 bits so segment length can be between 1 byte and 2 16 byte. The calculated linear address equals the physical memory address.
The 16-bit segment registers allow for 65,536 segments; each segment begins at a fixed offset equal to 16 times the segment number; the segment starting address granularity is 16 bytes. Each segment grants read-write access to 64 KiB (65,536 bytes) of address space (this limit is set by the 16-bit PC and SP registers; the processor does no ...