Skip to main content
Software Engineering

You are not logged in. Your edit will be placed in a queue until it is peer reviewed.

We welcome edits that make the post easier to understand and more valuable for readers. Because community members review edits, please try to make the post substantially better than how you found it, for example, by fixing grammar or adding additional resources and hyperlinks.

10
  • Is there a particular CPU or architecture you are interested in? Commented Mar 30, 2019 at 0:55
  • @1201ProgramAlarm Yes, x86 and x86_64. Commented Mar 30, 2019 at 0:58
  • 1
    The Intel CPUs don't have a "user mode". They have several modes of operation. The common separation between user code and operating system code is handled using "privilege levels" and other restrictions controlled thru the segment registers and paging tables. Device drivers can reside somewhere in between. Consult the Intel documentation. Commented Mar 30, 2019 at 1:19
  • @1201ProgramAlarm What do you mean there is no user mode in Intel CPUs, do you mean it is not formally called "user mode"? because based on what I have read, an x86 CPU for example have 4 protection rings, ring 0 is the most privileged (which we can call kernel mode), and ring 3 is the least privileged (which we can call user mode). Commented Mar 30, 2019 at 10:52
  • There's nothing called "user mode" in the documentation. Applications would run at Protection Level 3. The CPU isn't in this mode. The protection level is part of the thread properties (CS and SS registers). Commented Mar 30, 2019 at 12:51