Editing Instructions per second (section)

== {{anchor|MIPS}} Millions of instructions per second (MIPS)==
{{distinguish|MIPS architecture}}
The speed of a given CPU depends on many factors, such as the type of instructions being executed, the execution order and the presence of branch instructions (problematic in CPU pipelines). CPU instruction rates are different from clock frequencies, usually reported in [[hertz|Hz]], as each instruction may require several clock cycles to complete or the processor may be capable of executing multiple independent instructions simultaneously. MIPS can be useful when comparing performance between processors made with similar architecture (e.g. Microchip branded microcontrollers), but they are difficult to compare between differing [[CPU architecture]]s.<ref>{{cite web|url=http://www.ibmsystemsmag.com/mainframe/enewsletterexclusive/9806p1.aspx|title=Don't be Misled by MIPS|author=Ted MacNeil|publisher=IBM magazine|access-date=2009-11-15|archive-url=https://web.archive.org/web/20120723080942/http://www.ibmsystemsmag.com/mainframe/tipstechniques/systemsmanagement/Don-t-Be-Misled-By-MIPS/|archive-date=2012-07-23|url-status=dead}}</ref> This led to the term "Meaningless Indicator of Processor Speed,"<ref>{{cite book
| url = https://books.google.com/books?id=LqabAgAAQBAJ&dq=%22meaningless+indicator+of+processor+speed%22+book&pg=PT45
| title = System Performance Tuning
| page = 32
| date = 2002
| isbn = 9780596002848
| last1 = Musumeci
| first1 = Gian-Paolo D.
| last2 = Loukides
| first2 = Mike
| last3 = Loukides
| first3 = Michael Kosta
| publisher = "O'Reilly Media, Inc."
}}</ref> or less commonly, "Meaningless Indices of Performance," <ref>{{cite magazine
| url = https://archive.org/stream/PC-Mag-1987-11-24#page/n105/mode/2up
| title = The Best of Both Worlds: Mac II vs. IBM PS/2 Model 80
| page = 105
| date = November 24, 1987
| magazine = PC Magazine
}}</ref> being popular amongst technical people by the mid-1980s.

For this reason, MIPS has become not a measure of instruction execution speed, but task performance speed compared to a reference. In the late 1970s, minicomputer performance was compared using ''[[VAX]] MIPS'', where computers were measured on a task and their performance rated against the [[VAX-11#VAX-11/780|VAX-11/780]] that was marketed as a ''1 MIPS'' machine. (The measure was also known as the ''VAX Unit of Performance'' or '''VUP'''.) 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&nbsp;MIPS.

Many minicomputer performance claims were based on the [[Fortran]] version of the [[Whetstone (benchmark)|Whetstone benchmark]], giving Millions of Whetstone Instructions Per Second (MWIPS).   The VAX 11/780 with FPA (1977) runs at 1.02&nbsp;MWIPS.

Effective MIPS speeds are highly dependent on the programming language used. The Whetstone Report has a table showing MWIPS speeds of PCs via early interpreters and compilers up to modern languages. The first PC compiler was for [[BASIC]] (1982) when a 4.8&nbsp;MHz 8088/87 CPU obtained 0.01&nbsp;MWIPS. Results on a 2.4&nbsp;GHz Intel Core 2 Duo (1 CPU 2007) vary from 9.7&nbsp;MWIPS using BASIC Interpreter, 59&nbsp;MWIPS via BASIC Compiler, 347&nbsp;MWIPS using 1987 Fortran, 1,534&nbsp;MWIPS through HTML/Java to 2,403&nbsp;MWIPS using a modern [[C (programming language)|C]]/[[C++]] compiler.

For the most early [[8-bit computing|8-bit]] and [[16-bit computing|16-bit]] [[microprocessor]]s, performance was measured in [[1000 (number)|thousand]] instructions per second (1000&nbsp;kIPS = 1&nbsp;MIPS).

''zMIPS'' refers to the MIPS measure used internally by [[IBM]] to rate its [[Mainframe computer|mainframe]] servers ([[zSeries]], [[IBM System z9]], and [[IBM System z10]]).

''Weighted million operations per second (WMOPS)'' is a similar measurement, used for audio codecs.