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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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Is CLWB and PCOMMIT instructions available in gcc? If yes, in which version?

Are Intel's non-volatile memory instructions CLWB and PCOMMIT available in gcc ? If yes, starting from which gcc version are they available?
rojo
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clflush implementation: Why's m8 in "Flushes cache line containing m8"?

The clflush description in Intel document says that "Flushes cache line containing m8.". Also, m8 means "a byte from memory" from Intel document. I'm confused about why it is only m8, which is only one byte. Because for a 32-bit or 64-bit system,…
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Instruction Execution in MIPS

This is an abstract view of the implementation of the MIPS subset showing the major functional units and the major connections between them Why we need to add the result of (PC+4) with instruction address? I know that the PC (Program Counter) is a…
Reem Aljunaid
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On a Cortex M0 how expensive is a floating point compare vs an integer compare?

So I'm working on an embedded project that needs to compute floating point numbers. Obviously there's various ways to estimate the output and reduce compute cycles. My question is, how expensive is a floating point compare vs an integer compare…
jliu83
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Checking whether a given assembly file should run on a given processor

I'd like to assembly an x86 file while ensuring that the code will run on a given processor, without having to test it on a processor emulator. Is there a tool/technique which would allow me to do some sort of x86 instruction classification…
anol
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Matlab-Using a function to command a function generator

I have this function to send a command via GPIB connection to a Function generator (Stanford Research Systems, Synthesized Function Generator, model DS345) to change it's amplitude, frequency, and offset. However, when I uncomment the…
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Backwards compatibility of ARM v7 ISA to ARM v2 ISA

I'm currently in the early stages of a school project that involves analyzing the power draw of different types of processor cores. I'm looking to compare the relative power and performance measurements of a hardcore and softcore processor;…
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Designing Efficient memory for an Instruction Set Simulator

I'm designing an Instruction Set Simulator in C++, which is comprised of classes for the CPU, memory and the instruction set itself. I am currently trying to design my memory class, which will consist of the uint32_t data type. Basically the memory…
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8085 Instruction: JMP - Number of machine cycles when condition is not satisfied?

The machine code for the JMP instruction comprises of: opcode - 11CCC010 (where CCC is the state of the flag bit used to set the condition) 8 bits and address for the jump - let's say a 16 bit address. First there is a fetch operation of the opcode…
aste123
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direct access to Objective-C's isa is Deprecated in favor of object_getClass()

Here is my Code I want to change: if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.stringClass)) { isClass = JKClassString; } else if(JK_EXPECT_T(object->isa == encodeState->fastClassLookup.numberClass)) { isClass =…
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How Are Typecasts in C Implemented?

From the perspective of an application programmer, typecasts just work. With some syntax, the unsigned representation of an integer can act as a signed integer value less than INT_MAX. What are the algorithms that perform these conversions and what…
seewalker
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Can a compiler generate an output directly to the microprogramming level instead of the instruction set level?

I was wondering whether any given compiler can generate an output directly to the micro architecture level instead of the ISA level. I understand that the microprogramming level is not being used usually these days and the hardware executes…
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Dummy operations handling of Intel processor

Admittedly, I have a bit silly question. Basically, I am wondering if there are some special mechanisms provided by Intel processors to efficiently execute a series of dummy, i.e., NOP instructions? For instance,I could imagine there could be some…
reinhard
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Clang vs gcc floating point performance on ARM

I was trying out clang compiler and wanted to check its performance vs tradational gcc. I found out that its performance in terms of floating point operations is very bad compared to gcc (almost 30%). I compared the assembly files of my code with…
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How to run Windows from an emulator on a non x86 host machine?

Windows runs on x86 based CPUs only. Is it possible to make Windows run on non-x86 architecture CPUs like POWER, SPARC, ARM, etc.? I know that there is a program viz., Virtual PC 7 for Mac that allows Windows to be run on PowerPC inside MacOS but…
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