BogoMips

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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.

[edit] Proper BogoMips ratings

As a very approximate guide, the BogoMips can be pre-calculated by the following table. The given rating is typical for that CPU with the then current Linux version. The index is the ratio of "BogoMips per clock speed" for any CPU to the same for an Intel 386DX CPU, for comparison purposes.

System	Rating	Index
Intel 8088	clock * 0.004	0.02
Intel/AMD 386SX	clock * 0.14	0.8
Intel/AMD 386DX	clock * 0.18	1 (definition)
Motorola 68030	clock * 0.25	1.4
Cyrix/IBM 486	clock * 0.34	1.8
Intel Pentium	clock * 0.40	2.2
Intel 486	clock * 0.50	2.8
AMD 5x86	clock * 0.50	2.8
MIPS R4000/R4400	clock * 0.50	2.8
Motorola 8081	clock * 0.65	3.6
Motorola 68040	clock * 0.67	3.7
PowerPC 603	clock * 0.67	3.7
Intel StrongARM	clock * 0.66	3.7
NexGen Nx586	clock * 0.75	4.2
PowerPC 601	clock * 0.84	4.7
Alpha 21064/21064A	clock * 0.99	5.5
Alpha 21066/21066A	clock * 0.99	5.5
Alpha 21164/21164A	clock * 0.99	5.5
Intel Pentium Pro	clock * 0.99	5.5
Cyrix 5x86/6x86	clock * 1.00	5.6
Intel Pentium II/III	clock * 1.00	5.6
AMD K7/Athlon	clock * 1.00	5.6
Intel Celeron	clock * 1.00	5.6
Intel Itanium	clock * 1.00	5.6
MIPS R4600	clock * 1.00	5.6
Intel Itanium 2	clock * 1.49	8.3
Alpha 21264	clock * 1.99	11.1
Centaur VIA	clock * 1.99	11.1
AMD K5/K6/K6-2/K6-III	clock * 2.00	11.1
AMD Duron/Athlon XP	clock * 2.00	11.1
UltraSparc II	clock * 2.00	11.1
Pentium MMX	clock * 2.00	11.1
Pentium 4	clock * 2.00	11.1
Intel Core 2 Duo	clock * 2.00	11.1
Centaur C6-2	clock * 2.00	11.1
PowerPC 604/604e/750	clock * 2.00	11.1
Motorola 68060	clock * 2.01	11.2
Intel Xeon (hyper-threading)	clock * 3.97	22.1
Hitachi SH-4	clock * 1
IBM S390	not enough data (yet)
Intel ARM	not enough data (yet)

With the 2.2.14 linux kernel, a caching setting of the CPU state was moved from behind to before the BogoMips calculation. Although the BogoMips algorithm itself wasn't changed, from that kernel onward the BogoMips rating for then current Pentium CPUs came out double. The changed BogoMips outcome had no effect on real processor performance.

Full and complete information and details about BogoMips, and hundreds of reference entries can be found in the BogoMips mini-Howto (see below).