In C++, Why is a boolean 1 byte and not 1 bit of size? Why aren’t there types like a 4-bit or 2-bit integers? I’m missing out the above things when writing an emulator for a CPU 13 Answers 13
What is the difference between Trap and Interrupt? If the terminology is different for different systems, then what do they mean on x86? 10 Answers 10
I am wondering how much of Ulrich Drepper’s What Every Programmer Should Know About Memory from 2007 is still valid. Also I could not find a newer version than 1.0 or an errata. (Also in PDF form on Ulrich Drepper’s own site: https://www.akkadia.org/drepper/cpumemory.pdf) 3 Answers 3
It is unclear to me how the compiler will automatically know to compile for 64-bit when it needs to. How does it know when it can confidently target 32-bit? I am mainly curious about how the compiler knows which architecture to target when compiling. Does it analyze the code and make a decision based on … Read more
What is the difference between a core and a processor? I’ve already looked for it on Google, but I only get definitions for multi-core and multi-processor, which is not what I am looking for. 7 Answers 7
In order to mitigate against kernel or cross-process memory disclosure (the Spectre attack), the Linux kernel1 will be compiled with a new option, -mindirect-branch=thunk-extern introduced to gcc to perform indirect calls through a so-called retpoline. This appears to be a newly invented term as a Google search turns up only very recent use (generally all … Read more
I’ve been racking my brain for a week trying to complete this assignment and I’m hoping someone here can lead me toward the right path. Let me start with the instructor’s instructions: Your assignment is the opposite of our first lab assignment, which was to optimize a prime number program. Your purpose in this assignment … Read more
How can the theoretical peak performance of 4 floating point operations (double precision) per cycle be achieved on a modern x86-64 Intel CPU? As far as I understand it takes three cycles for an SSE add and five cycles for a mul to complete on most of the modern Intel CPUs (see for example Agner … Read more
Here is a piece of C++ code that shows some very peculiar behavior. For some strange reason, sorting the data (before the timed region) miraculously makes the loop almost six times faster. #include <algorithm> #include <ctime> #include <iostream> int main() { // Generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = … Read more
