x86-64

What x86-64 instructions are used to enable/disable other cores/processors and how does one start executing code on them? Is there documentation somewhere on how this is done by the operating system? Pretty painful to get an x86 up and going... it is not so much in the cores as in the APIC system. You need to look into the docs for your chipset, tends to be pretty much hidden unfortunately. You will have to be at the kernel level, definitely. Looking at Linux sounds like a good idea. Assuming you're talking about implementing a kernel.... My understanding is it's largely based on this document

Background: We have acquired a software product that builds to a 32-bit Windows application in Visual Studio. We wish to port this application to 64-bit. A mission-critical component of this code is a black-box static library (.a file) originally built using gFortran by a third party. The original developer has since passed away, and the Fortran source we were able to get was incomplete and not the version this library was built off of (and contains critical bugs not present in the compiled library). They did not use a VCS. Problem: I would like to create a 64-bit static library whose code is

I'm working on arithmetic for multiplication of very long integers (some 100,000 decimal digits). As part of my library I to add two long numbers. Profiling shows that my code runs up to 25% of it's time in the add() and sub() routines, so it's important they are as fast as possible. But I don't see much potential, yet. Maybe you can give me some help, advice, insight or ideas. I'll test them and get back to you. So far my add routine does some setup and then uses a 8-times unrolled loop: mov rax, QWORD PTR [rdx+r11*8-64] mov r10, QWORD PTR [r8+r11*8-64] adc rax, r10 mov QWORD PTR [rcx+r11*8

It is suggested that on Linux, GPU be found with the command lspci | grep VGA . It works fine on Ubuntu but when I try to use the same on CentOS, it says lspci command is not found. How can I check for the GPU card on CentOS. And note that I'm not the administrator of the machine and I only use it remotely from command line. I intend to use the GPU as a GPGPU on that machine, but first I need to check if it even has one. Have you tried to launch /sbin/lspci or /usr/sbin/lspci ? This assumes you have proprietary drivers installed, but issue the following command... nvidia-smi The output should

Consider the following code: #include <iostream> #include <chrono> using Time = std::chrono::high_resolution_clock; using us = std::chrono::microseconds; int main() { volatile int i, k; const int n = 1000000; for(k = 0; k < 200; ++k) { auto begin = Time::now(); for (i = 0; i < n; ++i); // <-- auto end = Time::now(); auto dur = std::chrono::duration_cast<us>(end - begin).count(); std::cout << dur << std::endl; } return 0; } I am repeatedly measuring the execution time of the inner for loop . The results are shown in the following plot (y: duration, x: repetition): What is causing the decreasing