Last Edit July 22, 2001
The initial version of any design is almost guarenteed not to be the
best solution. It is always possible to improve on an existing design,
hardware or software, just as it is always possible to edit a manuscript.
The trick is in knowing when to start and stop the process, also known
as the endless loop.
Design optimization should be performed once an initial version of the
design has been drafted at the block-diagram level. The design should
be reviewed for optimization under the constraints of the established
design objectives. It should also be reviewed for optimization using
the particular characteristics of the technology and array series selected.
A second design optimization review should be performed once the macro
conversion has been accomplished. The first step in this process is another
review of the chosen macro library. Familiarity with the macros available
will be invaluable in contributing to an optimized final design. The process
is shown in Figure 4-1.
Overview of Design Process - Objectives and Optimization
It has been shown that familiarity with the macro library is even
more important than previous design experience! Something many designers
argue with until faced with a case in point.
After reviewing the steps required to solve the simple case study example,
it should be obvious that the selection of macros to solve a circuit implementation
is much more complex than simply selecting the macros that appear to solve
the equation. Timing, cell utilization and power dissipation are integrated
elements that must be considered in parallel during the design
Design automation tools are moving in the direction of design synthesis
and design review-for-criteria. Example systems are the NCR ViSys Design
Advisor available on the Mentor Graphics and VCR-supported CAE workstations.
A future expansion to that system is the NCR design synthesis tool. Design
synthesis tools will become more prevalent over the next few years. They
should be considered as a tool to assist the designer, not to replace
the designer. [This was written in 1991-4 so there are presumably more
systems available. Check the current literature for other references.]