Introduction to Computer Systems - Fundamentals of Computer Organization and Architecture - page 4

TABLE 1.1 Four Decades of Computing

Feature Batch Time-sharing Desktop Network

Decade 1960s 1970s 1980s 1990s

Location Computer room Terminal room Desktop Mobile

Users Experts Specialists Individuals Groups

Data Alphanumeric Text, numbers Fonts, graphs Multimedia

Objective Calculate Access Present Communicate

Interface Punched card Keyboard & CRT See & point Ask & tell

Operation Process Edit Layout Orchestrate

Connectivity None Peripheral cable LAN Internet

Owners Corporate computer

centers

Divisional IS shops Departmental
end-users

Everyone

CRT, cathode ray tube; LAN, local area network.

The pervasiveness of the Internet created interest in network computing and more
recently in grid computing. Grids are geographically distributed platforms of com-
putation. They should provide dependable, consistent, pervasive, and inexpensive
access to high-end computational facilities.
Table 1.1 is modified from a table proposed by Lawrence Tesler (1995). In this
table, major characteristics of the different computing paradigms are associated with
each decade of computing, starting from 1960.

1.2. ARCHITECTURAL DEVELOPMENT AND STYLES

Computer architects have always been striving to increase the performance of their
architectures. This has taken a number of forms. Among these is the philosophy that
by doing more in a single instruction, one can use a smaller number of instructions to
perform the same job. The immediate consequence of this is the need for fewer
memory read

write operations and an eventual speedup of operations. It was also
argued that increasing the complexity of instructions and the number of addressing
modes has the theoretical advantage of reducing the “semantic gap” between the
instructions in a high-level language and those in the low-level (machine) language.
A single (machine) instruction to convert several binary coded decimal (BCD)
numbers to binary is an example for how complex some instructions were intended
to be. The huge number of addressing modes considered (more than 20 in the
VAX machine) further adds to the complexity of instructions. Machines following
this philosophy have been referred to as complex instructions set computers
(CISCs). Examples of CISC machines include the Intel Pentium TM , the Motorola
MC68000 TM , and the IBM & Macintosh PowerPC TM .
It should be noted that as more capabilities were added to their processors,
manufacturers realized that it was increasingly difficult to support higher clock
rates that would have been possible otherwise. This is because of the increased

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