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The various addressing modes that are defined in a given instruction set architecture define how the machine language instructions in that architecture identify the operand(s) of each instruction. An addressing mode specifies how to calculate the effective memory address of an operand by using information held in registers and/or constants ...
PDP-11 processor speed varies by model, memory configuration, op code, and addressing modes. Instruction timings have up to three components, fetch/execute of the instruction itself and access time for the source and the destination. The last two components depend on the addressing mode.
AMD's 64-bit extension to the original instruction set make relatively few changes to 32-bit addressing, with the most significant being that in long mode, 64-bit addressing is the default. 64-bit registers (RAX, RBX, RCX, etc.) are used rather than 32-bit registers for address computation.
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 reuse. [11] more operands—some CISC machines permit a variety of addressing modes that allow more than 3 operands (registers or memory accesses), such as the VAX "POLY" polynomial evaluation instruction.
Architectures typically allow instructions to include some combination of operand addressing modes: Direct The instruction specifies a complete address Immediate The instruction specifies a value rather than an address Indexed The instruction specifies a register to use as an index. In some architecture the index is scaled by the operand length ...
In computer engineering, an orthogonal instruction set is an instruction set architecture where all instruction types can use all addressing modes. It is " orthogonal " in the sense that the instruction type and the addressing mode may vary independently.
A complex instruction set computer (CISC / ˈ s ɪ s k /) is a computer architecture in which single instructions can execute several low-level operations (such as a load from memory, an arithmetic operation, and a memory store) or are capable of multi-step operations or addressing modes within single instructions.
The Simplified Instruction Computer has three instruction formats, and the Extra Equipment add-on includes a fourth. The instruction formats provide a model for memory and data management. Each format has a different representation in memory: Format 1: Consists of 8 bits of allocated memory to store instructions.