NEXT (Legacy H/W S/W Design Partition)
ASIC - Application-Specific Integrated Circuit
The cost of developing an ASIC has to be compared with the cost
of using an existing part. The existing part may not perform
the required function exactly, requiring either a design specification
change, or some additional glue logic to adapt the part
to the application.
More than one ASIC may be needed under any of the following
- application specific functions are physically distant
- application specific functions require different technologies
- application specific functions are just too big for one ASIC
- it is desired to split the cost and risk or reuse part of the system
Factors to consider on a per chip basis:
- power consumption limitation (powers above 5 Watts need special attention)
- die size limitation (above 11 mm on a side might escalate cost per mm²)
- speed of operation --- clock frequencies above 1~GHz raise issues
- special considerations :
- special static or dynamic RAM needs
- analogue parts - can these also be integrated onto the ASIC ?
- high power/voltage output capabilities for load control: e.g.~motors.
- availability of a developed module for future reuse.
H/W versus S/W Design Partition Principles
Many functions can be realised in software or hardware.
Decide what to do in hardware:
- Physical I/O (line drivers/transducers/media interfaces),
- Highly compute-intensive, fixed functions,
what to do on custom processors:
- Bit-oriented operations,
- Highly compute-intensive SIMD,
- Other algorithms with custom data paths,
- Algorithms that might be altered post tape out.
and what to do in S/W on standard cores:
- Highly-complex, non-repetitive functions,
- Low-throughput computations of any sort,
- Functions that might be altered post tape out.
- As much as possible.