Instructions per second

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Instructions per second (IPS) is a measure of a computer's processor speed. Many reported IPS values have represented "peak" execution rates on artificial instruction sequences with few branches, whereas realistic workloads consist of a mix of instructions and even applications, some of which take longer to execute than others. The performance of the memory hierarchy also greatly affects processor performance, an issue barely considered in MIPS calculations. Because of these problems, researchers created standardized tests such as SPECint to (maybe) measure the real effective performance in commonly used applications, and raw IPS has fallen into disuse.

The term is commonly used in association with a numeric value such as thousand instructions per second (kIPS), million instructions per second (MIPS), or Million Operations per Second (MOPS).

1 Thousand instructions per second
2 Million instructions per second
3 Timeline of instructions per second
4 See also

[edit] Thousand instructions per second

A thousand instructions per second (kIPS) is rarely used, as most current microprocessors can execute several million instructions per second. The thousand means 1000 not 1024.

kIPS is also a common joke name for 16 bit microprocessor designs developed in undergraduate computer engineering courses that use the text Computer Organization and Design by Patterson and Hennessy (ISBN 1-55860-428-6), which explains computer architecture concepts in terms of the MIPS architecture. Such architectures tend to be scaled down versions of the MIPS R2000 architecture.

[edit] Million instructions per second

Critics of the term refer to it by backronyms such as "Meaningless Indication of Processor Speed" or "Meaningless Information on Performance for Salespeople" or "Meaningless Integer Performance Spec". In Linux and UNIX circles MIPS are often referred to as bogoMIPS. MIPS are not comparable between CPU architectures.

The floating-point arithmetic equivalent of MIPS is FLOPS, to which the same cautions apply.

In the 1970s, minicomputer performance was compared using VAX MIPS, where computers were measured on a task and their performance rated against the VAX 11/780 that was marketed as a "1 MIPS" machine. (The measure was also known as the "VAX Unit of Performance" or VUP. Though orthographically incorrect, the "S" in "VUPs" is sometimes written in upper case.) This was chosen because the 11/780 was roughly equivalent in performance to an IBM System/370 model 158-3, which was commonly accepted in the computing industry as running at 1 MIPS.

Most 8-bit and early 16-bit microprocessors have a performance measured in kIPS (thousand instructions per second), which equals 0.001 MIPS. The first general purpose microprocessor, the Intel i8080, ran at 640 kIPS. The Intel i8086 microprocessor, the first 16-bit microprocessor in the line of processors made by Intel and used in IBM PCs, ran at 800 kIPS. Early 32-bit PCs (386) ran at about 3 MIPS.

zMIPS refers to the MIPS measure used internally by IBM to rate its mainframe servers (zSeries and System z9). Analyst firm Isham Research has lately coined the term kMIPS (kilo-million instructions per second) to measure the processor speeds in IBM's largest servers.

[edit] Timeline of instructions per second

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Processor	IPS	Year	Source
Pencil and Paper	0.0119 IPS	1892	[1]
Intel 8080	640 kIPS at 2 MHz	1974
Motorola 68000	1 MIPS at 8 MHz	1979
Intel 386DX	8.5 MIPS at 25 MHz	1988
Intel 486DX	54 MIPS at 66 MHz	1992
PowerPC 600s (G2)	35 MIPS at 33 MHz	1994
Intel Pentium Pro	541 MIPS at 200 MHz	1996	[2]
ARM 7500FE	35.9 MIPS at 40 MHz	1996
PowerPC G3	525 MIPS at 233 MHz	1997
Zilog eZ80	80 MIPS at 50 MHz	1999	[3]
Intel Pentium III	1354 MIPS at 500 MHz	1999
AMD Athlon	3561 MIPS at 1.2 GHz	2000
AMD XP 2400+	5935 MIPS at 2.0 GHz	2002
Pentium 4 Extreme Edition	9726 MIPS at 3.2 GHz	2003
ARM Cortex A8	2000 MIPS at 1.0 GHz	2005	[4]
Xbox360 IBM "Xenon" Single Core	6400 MIPS at 3.2 GHz	2005
AMD Athlon FX-57	12000 MIPS at 2.8 GHz	2005
AMD Athlon 64 3800+ X2 (Dual Core)	14564 MIPS at 2.2 GHz	2005	[5]
AMD Athlon FX-60 (Dual Core)	18938 MIPS at 2.6 GHz	2006	[6]
Intel Core 2 X6800	27079 MIPS at 2.93 GHz	2006	[7]
IBM Cell BE (Single SPE)	25600 MIPS (FLOPS) at 3.2 GHz	2006	[8]
Intel Core 2 Extreme QX6700	61119 MIPS at 3.33 GHz	2006	[9]