[Top] [Next]
[Prev]
Chapter Review
In this chapter, we have examined the fundamental structure
of computers. A computer, like many digital systems, consists of data-path
and control. The data-path contains the storage elements (
registers)
that hold operands, the functional units (
ALUs, shifter registers)
that operate on data, and the interconnections (
buses)
between them.
The computer's control is nothing more than a finite state
machine. It cycles through a collection of states that fetch the next instruction
from memory, decode this instruction to determine its type, and then execute
the instruction. The control executes the instruction by asserting signals
to the data-path to cause it to move data from registers to functional units,
perform operations, and return the results to the registers.
Register transfer operations provide a notation for describing
functional unit operations and the data movements between registers and
functional units. The register transfer operations are normally written
in a form that is independent of the detailed interconnections supported
by the data-path.
Once the data-path interconnections are determined, we
replace each register transfer operation by a sequence of microoperations.
These correspond to detailed control signals to the data-path that must
be asserted to cause a register transfer operation to take place.
Computers are interesting because they are particularly
complex digital hardware systems. The data-path is not where this complexity
comes from. It comes from the control portion of the machine. In the next
chapter, we will look at ways to organize the complex control state machine
of a digital computer.
Further Reading
Unfortunately, most textbooks on logic design do not provide
much coverage on computer organization. After all, a detailed treatment
of computer architectures, instruction sets, and their implementation is
a topic for another book. Notable exceptions include Johnson and Karim,
Digital Design: A Pragmatic Approach, PWS Engineering, Boston,
1987, and Prosser and Winkel, The Art of Digital Design, 2nd ed.,
Prentice-Hall, Englewood Cliffs, NJ, 1987. Both of these have several chapters
on computer structures and their implementations in hardware.
For a historical perspective on how computer architectures
have developed, a wonderful book is D. Patterson and J. Hennessy, Computer
Architecture: A Quantitative Approach, Morgan-Kaufmann, Redwood City,
CA, 1990.
[Top]
[Next] [Prev]
This file last updated on 07/16/96 at 04:05:25.
randy@cs.Berkeley.edu;