U. Glaeser

enchmark took between 15.7 and 5115 s to run on various Z80 microprocessor systems [7]. Performance
is usually based on processor performance. But, performance may be based on other features: graphics
performance, sound quality, physical size, power consumption, main memory size, disk drive speed, or
system configuration capability.
Speed of execution on a standard benchmark application is important for a CPU. The size in megabytes
is the main measure for disk drives, although access time and data throughput are often important factors
for disk drives as well. Also, nonfunctional features are often important performance features for practical
computer systems. Typical nonfunctional features are: reliability, compatibility, scalability, and flexibility.
These features are not as easy to measure as speed or size.
Generally, there is an upper limit to performance of a technology at any point in time: the fastest
processor available, the biggest disk drive, etc. Exceeding this limit requires either the development of
new technology, or parallel operation (multiple CPUs, multiple disk drives, etc.). Other constraints, such
as physical size or operating power, may place an absolute upper threshold on performance. In practice,
the main constraint is usually the price.
The performance of systems may be determined by marketing decisions of vendors. Rather than
produce a variety of systems, a vendor may make one fast system, and slow the clock speed to produce
a range of slower systems. Recently a computer vendor shipped a computer system with performance on
demand—you pay to enable existing processors to be used. Thus, it may not always be possible to use
the performance that is possible without paying an additional price.
Applications
Computers in themselves are of little interest to most people. The importance is what the computer can
do—the applications. A “killer app” is a computer program that causes a computer to become popular.
VisiCalc, the first electronic spreadsheet program, was a killer app for the Apple II computer. Over the
years there have been a number of important applications that have driven the sales of computers. Selected
applications are listed in Table 4.2 [8–22].
TABLE 4.2
© 2002 by CRC Press LLC
Selected Applications Driving Computer Usage and Sales
Year Application Category Typical Computer Program Ref.
1889 Census tabulation Hollerith E. T. S. — [8]
1943 Scientific calculations Harvard Mark 1 — [9]
1943 Cryptography Collosus — [10]
1945 Ballistic calculations ENIAC — [11]
1950 Census analysis UNIVAC 1 — [12]
1951 Real time control Whirlwind — [13]
1955 Payroll IBM 650 — [14]
1960 Data processing UNIVAC II COBOL [15]
1961 Mass billing IBM 1401 — [16]
1964 Large scale scientific computing CDC 6600 — [17]
1965 Laboratory equipment control PDP-8 — [18]
1968 Timeshared interactive computing PDP-10 TOPS-10 [19]
1970 Email PDP-10 mail —
1971 Text editing PDP-11 UNIX ed, roff [20]
1974 Data base management systems IBM 360 IMS [21]
1975 Video games Commodore PET — —
1980 Word processing Z-80 with CP/M WordStar —
1980 Spreadsheet Apple-II VisiCalc —
1985 CAD/CAM Apollo workstation — —
1986 Desktop publishing Macintosh PageMaker —
1994 WWW browser PC plus servers Mosaic [22]
1997 E-commerce PC plus servers Netscape —
1999 Realistic rendered 3D games PC Quake —
2000 Video capture and editing iMAC iMovie —