When I try to install Ubuntu I get the message

This kernel requires CMOV not present on cpu

What does this mean and how do I get around it?

  • What ancient / incompatible(?) CPU do you have? (or machine if you don't know the exact CPU model) – Lekensteyn Mar 24 '12 at 19:54

CMOV stands for "conditional move" and speeds up code by avoiding "if-thens" and therefore the necissity of branch-prediction.

It's available on .686 architecture and above which equals Pentium2 or so(guessing). So your computer is simply too old, maybe P1 or VIA or something.


The CMOV (conditional move) instruction was added to Intel CPUs with the release of the Pentium Pro, and shortly after that for most other x86 CPU manufacturers.

The kernel shipped with Ubuntu 10.10 dropped support for old i586 CPUs by requiring this extension, so you will have difficulty running anything newer on this system.

At this point, I would suggest you try running Ubuntu 10.04 (Lucid) on the machine, but seriously consider upgrading or retiring the system.

  • There's one caveat. There are only a handful of manufacturers and by numbers of produced units you're right that the majority added cmovb. Cyrix, however, didn't. We've had this problem not with the kernel but with the software we sell. +1 – 0xC0000022L Mar 22 '13 at 13:24

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