Joel S. Emer (born March 2, 1954) is a pioneer in

computer performance In computing, computer performance is the amount of useful work accomplished by a computer system. Outside of specific contexts, computer performance is estimated in terms of accuracy, efficiency and speed of executing computer program instructio ...

analysis techniques and a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

architect. He is currently a researcher at

Nvidia Nvidia CorporationOfficially written as NVIDIA and stylized in its logo as VIDIA with the lowercase "n" the same height as the uppercase "VIDIA"; formerly stylized as VIDIA with a large italicized lowercase "n" on products from the mid 1990s to ...

, and a Professor of the Practice at

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the mo ...

, and was formerly an

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...

Fellow. He was the 2009 recipient of the

Eckert–Mauchly Award The Eckert–Mauchly Award recognizes contributions to digital systems and computer architecture. It is known as the computer architecture community’s most prestigious award. First awarded in 1979, it was named for John Presper Eckert and John ...

, an

ACM ACM or A.C.M. may refer to: Aviation * AGM-129 ACM, 1990–2012 USAF cruise missile * Air chief marshal * Air combat manoeuvring or dogfighting * Air cycle machine * Arica Airport (Colombia) (IATA: ACM), in Arica, Amazonas, Colombia Computing * ...

IEEE The Institute of Electrical and Electronics Engineers (IEEE) is a 501(c)(3) professional association for electronic engineering and electrical engineering (and associated disciplines) with its corporate office in New York City and its operation ...

joint award for contributions to computer and digital systems architecture. Emer received his Ph.D. degree from the

University of Illinois, Urbana-Champaign The University of Illinois Urbana-Champaign (U of I, Illinois, University of Illinois, or UIUC) is a public land-grant research university in Illinois in the twin cities of Champaign and Urbana. It is the flagship institution of the Universi ...

under the supervision of Prof. Edward S. Davidson. His first job immediately after graduation was at

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...

where he initially worked on

VAX VAX (an acronym for Virtual Address eXtension) is a series of computers featuring a 32-bit instruction set architecture (ISA) and virtual memory that was developed and sold by Digital Equipment Corporation (DEC) in the late 20th century. The VA ...

performance evaluation and then on

Alpha Alpha (uppercase , lowercase ; grc, ἄλφα, ''álpha'', or ell, άλφα, álfa) is the first letter of the Greek alphabet. In the system of Greek numerals, it has a value of one. Alpha is derived from the Phoenician letter aleph , whic ...

performance evaluation. As a consequence of his performance evaluation work, he became a pioneer in the quantitative approach to

computer architecture In computer engineering, computer architecture is a description of the structure of a computer system made from component parts. It can sometimes be a high-level description that ignores details of the implementation. At a more detailed level, t ...

. In conjunction with the development and application of various performance analysis techniques, he contributed a variety of research and advanced development ideas that were incorporated into various VAX and Alpha designs. He is well known, along with his co-author Douglas W. Clark, for a seminal paper on the quantitative analysis of processor architectures, which was published in the 11th

International Symposium on Computer Architecture The International Symposium on Computer Architecture (ISCA) is an annual academic conference on computer architecture, generally viewed as the top-tier in the field. Association for Computing Machinery's Special Interest Group on Computer Archit ...

. That paper also contained the result that the

VAX-11/780 The VAX-11 is a discontinued family of 32-bit superminicomputers, running the Virtual Address eXtension (VAX) instruction set architecture (ISA), developed and manufactured by Digital Equipment Corporation (DEC). Development began in 1976. In ad ...

's performance was actually 0.5 MIPS instead of 1 MIPS as was previously claimed by DEC. That result helped popularize what Clark called the

iron law of processor performance In computer architecture, the iron law of processor performance (or simply iron law of performance) describes the performance trade-off between complexity and the number of primitive instructions that processors use to perform calculations. This f ...

that related

cycles per instruction In computer architecture, cycles per instruction (aka clock cycles per instruction, clocks per instruction, or CPI) is one aspect of a processor's performance: the average number of clock cycles per instruction for a program or program fragment. ...

(CPI), frequency and number of instructions to

. Emer has also contributed to

simultaneous multithreading Simultaneous multithreading (SMT) is a technique for improving the overall efficiency of superscalar CPUs with hardware multithreading. SMT permits multiple independent threads of execution to better use the resources provided by modern process ...

(SMT),

memory dependence prediction Memory dependence prediction is a technique, employed by high-performance out-of-order execution microprocessors that execute memory access operations (loads and stores) out of program order, to predict true dependencies between loads and stores at ...

via store sets, and

soft error In electronics and computing, a soft error is a type of error where a signal or datum is wrong. Errors may be caused by a defect, usually understood either to be a mistake in design or construction, or a broken component. A soft error is also a s ...

analysis, and led the development of the Asim simulator. In 2020, Emer was elected as a member into the

National Academy of Engineering The National Academy of Engineering (NAE) is an American nonprofit, non-governmental organization. The National Academy of Engineering is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy ...

for quantitative analysis of computer architecture and its application to architectural innovation in commercial microprocessors.

References

;Notes * Emer, Joel S.; Clark, Douglas W. (1984). "A characterization of processor performance in the VAX-11/780". ''Proceedings of the 11th Annual International Symposium on Computer Architecture''. pp. 301–310. {{DEFAULTSORT:Emer, Joel Living people 1954 births Purdue University alumni University of Illinois Urbana-Champaign alumni Digital Equipment Corporation people Intel people Fellows of the Association for Computing Machinery Fellow Members of the IEEE Computer hardware engineers American electrical engineers Place of birth missing (living people) Nvidia people