What is Bogo MIPS, DMIPS

Question

1. I have read about bogo on Wikipedia, but could not get clear idea. So what exactly is bogo mips? What does the table of rating and index for bogo mips for different processors mean?

2. Whats a dhrystone MIPS? Its significance. e.g. if some of my code needs 1000 MIPS on some processor, does the max. processor dhrystone specified for that CPU/processor be more than 1000 Dhrystone mips?

Answer 1

From Wikipedia:

BogoMips (from "bogus" and MIPS) is an unscientific measurement of CPU speed made by the Linux kernel when it boots, to calibrate an internal busy-loop. An oft-quoted definition of the term is "the number of million times per second a processor can do absolutely nothing."

BogoMips can be used to see whether it is in the proper range for the particular processor, its clock frequency, and the potentially present CPU cache. It is not usable for performance comparison between different CPUs.

Both Dhrystone and Whetstone are benchmarks which measure computing power. The former concentrates on string and integer operations and therefore is more representative of the ALU speed, while the latter primarily measures the FPU performance. Depending on your application one or the other is more representative of what you're doing.

Answer 2

Quote the Jargon File entry on BogoMIPS:

The number of million times a second a processor can do absolutely nothing. The Linux OS measures BogoMIPS at startup in order to calibrate some soft timing loops that will be used later on; details at the BogoMIPS mini-HOWTO. The name Linus chose, of course, is an ironic comment on the uselessness of all other MIPS figures.

In short, the one of least accurate benchmarks ever.

(The name is obviously based on bogus.)