---
title: Why CPU Time ≠ Wall Clock Time! - Computerphile
link: https://www.youtube.com/watch?v=xs5iOwkX9fU
source: youtube-com-computerphile
published: 2026-08-27T13:00:19Z
updated: 2026-09-08T01:47:14Z
first_seen: 2026-09-19T21:30:23.395188495Z
authors:
- Computerphile
summary: "The CPU can take time to find out the time, so how does it know the time? Matt Godbolt is the genius behind Compiler Explorer and the Godbolt BBC Micro Emulator, find more from him at godbolt.org \n\nComputerphile is supported by Jane Street. Learn more about them (and exciting career opportunities) at: https://jane-st.co/computerphile\n\nThis video was filmed and edited by Sean Riley.\n\nComputerphile is a sister project to Brady Haran's Numberphile. More at https://www.bradyharanblog.com"
content: extracted
html: 2026-08-27-why-cpu-time-wall-clock-time-computerphile.html
preview:
  file: 2026-08-27-why-cpu-time-wall-clock-time-computerphile.preview-91d5ead42f09.webp
  width: 256
  height: 192
  color: '#4a4f3c'
images:
- source: https://i.ytimg.com/vi/xs5iOwkX9fU/maxresdefault.jpg
  original:
    file: 2026-08-27-why-cpu-time-wall-clock-time-computerphile.image-763fcef3820a.jpg
    width: 1280
    height: 720
  color: '#383837'
- source: https://i1.ytimg.com/vi/xs5iOwkX9fU/hqdefault.jpg
  original:
    file: 2026-08-27-why-cpu-time-wall-clock-time-computerphile.image-4031e7f2acf3.jpg
    width: 480
    height: 360
  color: '#010101'
extra:
  thumbnail: https://i1.ytimg.com/vi/xs5iOwkX9fU/hqdefault.jpg
---

The CPU can take time to find out the time, so how does it know the time? Matt Godbolt is the genius behind Compiler Explorer and the Godbolt BBC Micro Emulator, find more from him at godbolt.org

Computerphile is supported by Jane Street. Learn more about them (and exciting career opportunities) at: https://jane-st.co/computerphile

This video was filmed and edited by Sean Riley.

Computerphile is a sister project to Brady Haran's Numberphile. More at https://www.bradyharanblog.com