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The Intel MCS-51 (commonly termed 8051) is a single-chip microcontroller (MCU) series developed by Intel in 1980 for use in embedded systems. The architect of the Intel MCS-51 instruction set was John H. Wharton. [1] [2] Intel's original versions were popular in the 1980s and early 1990s, and enhanced binary compatible derivatives remain ...
C = A+B needs two instructions. RISC — arithmetic instructions use registers only, so explicit 2-operand load/store instructions are needed: load a,reg1; load b,reg2; add reg1+reg2->reg3; store reg3,c; C = A+B needs four instructions. Unlike 2-operand or 1-operand, this leaves all three values a, b, and c in registers available for further ...
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.
For example, with two executions units, two new instructions are fetched every clock cycle by exploiting instruction-level parallelism, therefore two different instructions would complete stage 5 in every clock cycle and on average the number of clock cycles it takes to execute an instruction is 1/2 (CPI = 1/2 < 1).
An instruction set architecture (ISA) is an abstract model of a computer, also referred to as computer architecture.A realization of an ISA is called an implementation.An ISA permits multiple implementations that may vary in performance, physical size, and monetary cost (among other things); because the ISA serves as the interface between software and hardware.
Registers are normally measured by the number of bits they can hold, for example, an 8-bit register, 32-bit register, 64-bit register, 128-bit register, or more.In some instruction sets, the registers can operate in various modes, breaking down their storage memory into smaller parts (32-bit into four 8-bit ones, for instance) to which multiple data (vector, or one-dimensional array of data ...
The IBM 704, 709, 704x and 709x store one instruction in each instruction word; IBM numbers the bit from the left as S, 1, ..., 35. Most instructions have one of two formats: Generic S,1-11 12-13 Flag, ignored in some instructions 14-17 unused 18-20 Tag 21-35 Y Index register control, other than TSX S,1-2 Opcode 3-17 Decrement 18-20 Tag 21-35 Y
Some instruction set architectures, such as Intel x86 and IBM/360 and its successors, have a load effective address instruction. [10] [11] This calculates the effective operand address and loads it into a register, without accessing the memory it refers to. This can be useful when passing the address of an array element to a subroutine.