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Undefined Instructions – will generate an invalid opcode (#UD) exception in all operating modes. [z] These instructions are provided for software testing to explicitly generate invalid opcodes. The opcodes for these instructions are reserved for this purpose. (3) , [aa] Intel Pentium [66] UD1 reg,r/m, [ab] UD2B reg,r/m [y] 0F B9 /r [ac] OIO, UD0,
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.
An opcode table (also called an opcode matrix) is a visual representation of all opcodes in an instruction set. It is arranged such that each axis of the table represents an upper or lower nibble, which combined form the full byte of the opcode. Additional opcode tables can exist for additional instructions created using an opcode prefix.
Some instruction sets have nearly uniform fields for opcode and operand specifiers, whereas others (e.g., x86 architecture) have a less uniform, variable-length structure. [10] [11] Instruction sets can be extended through the use of opcode prefixes which add a subset of new instructions made up of existing opcodes following reserved byte ...
EVEX.W is used to specify format of the prefetchable data (0:FP32, 1:FP64) The bottom bit of the opcode is used to indicate whether the AVX512 index register is considered a vector of sixteen signed 32-bit indexes (bit 0 not set) or eight signed 64-bit indexes (bit 0 set) The instructions all support operation masking by opmask registers.
x86 assembly language is a family of low-level programming languages that are used to produce object code for the x86 class of processors. These languages provide backward compatibility with CPUs dating back to the Intel 8008 microprocessor, introduced in April 1972.
For example, using AL as an accumulator and adding an immediate byte value to it produces the efficient add to AL opcode of 04h, whilst using the BL register produces the generic and longer add to register opcode of 80C3h. Another example is double precision division and multiplication that works specifically with the AX and DX registers.
The Intel BCD opcodes are a set of six x86 instructions that operate with binary-coded decimal numbers. The radix used for the representation of numbers in the x86 processors is 2. This is called a binary numeral system. However, the x86 processors do have limited support for the decimal numeral system.