wiki:laguna/faq

Laguna FAQ (Frequently Asked Questions)

BogoMIPs values appear lower then expected

The reported bogoMIPS value is indeed bogus in the case of the ARM11 mpcore and other more modern ARM processors. The processor has a hardware function that helps to make "tight loops" more efficient by implementing branch folding. When the software attempts to discover its bogomips it executes a function called delay with a number of instructions it wants to delay. The delay function is a "tight loop" and the branch instruction gets "folded" away causing the number of cycles to be far fewer than expected, yielding an incorrect value for bogomips.

For the Cavium cns3xxx processors, expect the following bogomips values:

  • dual-core 600Mhz cns3420 (GW2388): 239 bogomips each
  • single-core 300MHz cns3410 (GW2380): 119 bogomips

References:

​ * http://lists.infradead.org/pipermail/linux-arm-kernel/2010-January/008676.html ​ * http://lists.infradead.org/pipermail/linux-arm-kernel/2010-January/008912.html

Last modified 9 months ago Last modified on 01/30/2018 01:13:23 PM