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The Intel 8085 ("eighty-eighty-five") is an 8-bit microprocessor produced by Intel and introduced in March 1976. [2] It is the last 8-bit microprocessor developed by Intel. It is software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added interrupt and serial input/output features.
Below is the full 8086/8088 instruction set of Intel (81 instructions total). [2] These instructions are also available in 32-bit mode, in which they operate on 32-bit registers (eax, ebx, etc.) and values instead of their 16-bit (ax, bx, etc.) counterparts.
Intel hexadecimal object file format, Intel hex format or Intellec Hex is a file format that conveys binary information in ASCII text form, [10] making it possible to store on non-binary media such as paper tape, punch cards, etc., to display on text terminals or be printed on line-oriented printers. [11]
x86 assembly language has two primary syntax branches: Intel syntax and AT&T syntax. [6] Intel syntax is dominant in the DOS and Windows environments, while AT&T syntax is dominant in Unix-like systems, as Unix was originally developed at AT&T Bell Labs. [7] Below is a summary of the main differences between Intel syntax and AT&T syntax:
Intel x86 CPU family NOP: 1 0x90 [2] 0x90 is the one-byte encoding for XCHG AX,AX in 16-bit code and XCHG EAX,EAX in 32-bit code. In long mode, XCHG RAX,RAX requires two bytes, as it would begin with an REX.W prefix, making the encoding 0x48 0x90.
However, the encoding-strategy used still shows many traces from the 8008 and 8080 (and Z80). For instance, single-byte encodings remain for certain frequent operations such as push and pop of registers and constants; and the primary accumulator, the EAX register , employs shorter encodings than the other registers on certain types of operations.
An 8-bit register can store 2 8 different values. The range of integer values that can be stored in 8 bits depends on the integer representation used. With the two most common representations, the range is 0 through 255 (2 8 − 1) for representation as an binary number, and −128 (−1 × 2 7) through 127 (2 7 − 1) for representation as two's complement.
All x86 processors from the 8086 onward had the HLT instruction, but it was not used by MS-DOS prior to 6.0 [2] and was not specifically designed to reduce power consumption until the release of the Intel DX4 processor in 1994. MS-DOS 6.0 provided a POWER.EXE that could be installed in CONFIG.SYS and in Microsoft's tests it saved 5%. [3]