Category "x86"

memory bandwidth for many channels x86 systems

I'm testing the memory bandwidth on a desktop and a server. Sklyake desktop 4 cores/8 hardware threads Skylake server Xeon 8168 dual socket 48 cores (24 per so

What does this i386 os code mean? The code is for resetting the system

/* jump to reset vector. esp := 0 */ int main(int argc, char **argv) { PRINT("reset\n"); _eflags = 0; // interrupt disabled __asm__ __volatile__ ("\

Are there any instructions (other than those that use RIP-relative addressing) that are position dependent?

(This question refers specifically to x86/x86_64) I'm working on an application that needs to insert a small block of instructions at specific points within ano

Is a mov to a segmentation register slower than a mov to a general purpose register?

Specifically is: mov %eax, %ds Slower than mov %eax, %ebx Or are they the same speed. I've researched online, but have been unable to find a definitive an

how to understand if a CPU support ECC?

I have an old pc powered by an Intel Core2 Quad [email protected] (both Bios and linux dmidecode don't tell more than that), I can add that the CPU belongs to: Family

Finding the minimum value on a list Assembly Language GAS

I'm trying to find the minimum value of a list using assembly language. I'm trying to use -1 to compare all the other values to. my current code is data_items:

Finding the minimum value on a list Assembly Language GAS

I'm trying to find the minimum value of a list using assembly language. I'm trying to use -1 to compare all the other values to. my current code is data_items:

Find out higher bit with assembly language

I am new to assembly language. Please help me how to find the higher bits after these instruction MOV AX,08H MOV BX, 07H ADD AX,BX I know a little bit shiftin

Program in assembly x86 [closed]

I recently made a program with C++ and ASM. Can anyone help me make this code a more efficient one , in the ASM part or both. I would really a

Can modern x86 hardware not store a single byte to memory?

Speaking of the memory model of C++ for concurrency, Stroustrup's C++ Programming Language, 4th ed., sect. 41.2.1, says: ... (like most modern hardware) the

The most correct way to refer to 32-bit and 64-bit versions of programs for x86-related CPUs?

This question is about terminology for 32-bit vs. 64-bit x86. If I have 2 directories with source code of the same program - one for 32-bit Windows and another

Load only first byte into a register, from a string at a label

I am trying to load only the first byte in a register after data is passed into it for example if I have the following ASM code global _start section .data stri

Migrate to arm64 on AWS Lambda show error: Unable to import module 'encryptor-lambda'

I have a lambda function runs on Python 3.7 with architecture x86_64 before. Now I would like to migrate it to arm64 to use the Graviton processor and upgrade t

Why didn't x86 implement direct core-to-core messaging assembly/cpu instructions?

After serious development, CPUs gained many cores, gained distributed blocks of cores on multiple chiplets, numa systems, etc but still a piece of data has to p

What is the benefit of calling ioread functions when using memory mapped IO

To use memory mapped I/O, we need to first call request_mem_region. struct resource *request_mem_region( unsigned long start, u

Do UEFI DXE Drivers operate in real-mode? What about "ring -2" or "ring -3" code?

I asked a question referencing a mode sometimes referred to as ring -2 (System Management Mode) which can be exploited to create rootkits. There's also even a r

Is it possible to read a value from memory being written by another thread, so that it's neither the original nor final?

Suppose we have a variable in memory, which is constantly being updated by a thread of execution by doing something like MOV into it with alternating values (si

How to get the beginning address of a string instead of the address of a whole string

SORRY if i make you confuse about the question, but i don't know a better to describe it i'm trying to write a NASM program to reverse a string in place. i ha

Correctly disable Hardware Prefetching with MSR in Skylake

I am trying to disable hardware prefetching on my machine: CPU family: 6 Model: 78 Model name: Intel(R) Core(TM) i5-6200U CPU

Bit-twiddling Wizardry for Index of Min or Max Element in XMM/YMM/ZMM

Is there an instruction or efficient branchless sequence of instructions to figure out the INDEX of (not the value of) the largest (or smallest) element of an u