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Questions tagged [instruction-set]

Use for questions related to Instruction Set Architectures, ISA. For questions related to the inner workings of a CPU, use [cpu-architecture] instead.

An instruction set is a specification for a set of machine-readable instructions, or CPU instructions. An instruction set exists for all processing units including Graphics Processing Cores, Networking Card Processors as well at the CPU. The phrase "Instruction Set" usually implies the CPU type.

Each digital logic process which a processor can perform has an binary instruction code which caused the CPU to execute that exact instruction. An assembly language translates mnemonics into instruction codes. Instruction codes are likely to differ between different processor architectures. For example, the x86_64 instruction set for Intel CPU's includes additional 64 bit instructions (among others) for manipulating data 64 bits wide inside the CPU's core, which is an extension to the x86 32 bit capabilities of previous Intel CPU generations.

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Different ISA binary profiling results contradiction

I am doing profiling of my code written in CPP targeting RISC architecture. I have two binaries generated one for x86 and other for RISC-V. I have done profiling using perf and gprof. As per Theory of RISC and CISC architecture,but what I have got…
Yulia
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Is ARM’s RISC instruction set a subset of x86? If so, why can’t x86 run ARM software natively then?

From my limited understanding of instruction sets, ARM is a RISC architecture, meaning that there are significantly fewer/simpler instructions than x86 based processors. If this is the case, I would expect ARM’s instruction set to be a subset of…
user9146967
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Why the machine code of the ARM32 instruction cannot be found in ARM64 instruction set

Since ARM32 machine instructions can be executed directly on ARM64 processors, I thought that the machine code of the ARM32 instruction add r0, r0, r1 should be the same as that of one of these two ARM64 instructions: add w0, w0, w1 add x0, x0,…
xiaokaoy
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Clock cycles in a single 8080 instruction

From the book Code, it says that: The 8080 instruction requires anywhere from 4 to 18 clock cycles". Why would there be such a fluctuation between the number of clock cycles to execute an instruction. What would be an example of an instruction…
David542
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what is the use of MOVMSKB operation?

I want to ask what is the use for MOVMSKB operation? I try to find the documentation, but I cannot find the information related.
TIANYANG ZHANG
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Is there any suggestions to Monitor results? for Store and load instructions implemented using Data Memory

I am having difficulty in getting the Load and store instructions implemented in my Processor. I have Successfully implemented ALU RegisterFile now i want to add A Data Memory and Upgrade the Control unit. I don't have yet implemented the…
Amila Weerasinghe
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How do things work in the fetch phase of the instruction cycle?

There's something that confuses me, in Computer System Architecture(Morris Mano), Chapter 5, the book uses a simple microprocessor which has the following instruction cycle: e.g. LDA Operation: AR<---PC (T0) IR<---M[AR] (T1) PC<---PC+1 (T1) Decode…
azkabantutsagi666
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What does RAM actually stores,adress of the instructions or instruction itself in the form of 0s and 1s?

How does actually the instruction is executed,does the instructions is stored in the ram or only the adress of that instruction is stored in the ram And then using that instruction CPU gets the full instruction data to be executed
Sidramesh
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Risc processor the Negation of a register

We consider a RISC processor that have only a few command like DBNZ. I am trying to write code that writes the negation of a Register A into B and also second separate code that it should subtract A from B and put the result into C I am not sure…
ThePom
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do all 32bit processors follow the same instruction set

I read that instruction set varies from one processor to another. Say for an example, Instruction set in an Intel processor is different from an instruction set of an AMD processor. But If thats the case, how does device drivers of one hardware,…
sapphirebox001
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How does CODE 8086 command LOOPW works?

How does this "LOOPW 0100" works ?? http://ece425web.groups.et.byu.net/stable/labs/8086InstructionSet.html
Shujan S
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Confused about how an ARM32 processor distinguishes between a register and immediate instruction

I am looking at various instructions for an ARM32 processor, and am confused about how the processor is able to distinguish between an instruction that operates on registers and an instruction that operates with an immediate value. For example, in…
user13251577
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how to copy the register in hypothetical CPU ISA using assembly

Given following Instruction in a hypothetical CPU ISA with register space A-Z , write an assembly program to copy N bytes from address A to address B MOV C, 100 - Move a constant value 100 to register C LDR A, Addr – Load Register A with contents of…
Harish
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How many bits are needed to represent an instruction in a computer?

How many bits are needed to represent an instruction in a computer that has 53 different instructions, all of which are two addresses, when the computer has 65000-word memory ?
krishankantray
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Difference between Instruction set and Instruction set architecture?

can anyone explain them with differences? I searched for the differences all over the internet but unable to find them.
Jay V
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