66 COMPUTER ENGINEERING
Table 1. Design Activities, Metrics, and Environment Goals and Constraints
|
Design Activity |
Environment and [Metrics] |
|
Primary function and performance (e.g., memory) |
Market, the consumer of the system [Memory size in bits, operation rate in bits/sec) |
|
Human engineering |
Human factors criteria, competitive market factors |
|
Visual/aesthetics |
Market, other similar objects, the environment in which the object is to exist |
|
Acoustic noise |
Government standards, operating environment, market [Decibels in various frequency bands) |
|
Mechanical |
Shippability by various carriers, handling, assembly/disassembly time [Weight, floor area, volume, expandability, acceleration, mechanical frequency response] |
|
Electromagnetic radiation |
Government standards, must operate within intended environment [Power versus frequency] |
|
Power |
Operating environment, market [watts, voltage supply range] |
|
Cooling and environment |
Market, intended storage and operating environment, government standards [Heat dissipation, temperature range, airflow, humidity range, salinity, dust particle, hazardous gas] |
|
Safety |
Government standards |
|
Cost Cost/metric ratios |
[Cost/performance (its function) - cost/bit and cost/bit/sec, cost/weight, cost/area, cost/volume, cost/watt] |
|
Density metrics |
[Weight/volume, watts/volume, operation rate/volume] |
|
Power metrics |
[Operation rate/watt; efficiency = power out/power in] |
|
Reliability |
[Reliability - failure rate (mean time between failures), availability - mean time to repair) |
to meet cost, speed, number of users, data base size, language (programming), reliability, and interface constraints. Aside from the functional design problem, cooling and power design are significant for larger computers. For smaller computers, accessibility, acoustic noise, and visual considerations are significant because these machines become part of a local environment and must "fit in."
Cabinet Level. Since the cabinet is the lowest level component that users interface to and observe, physical design, visual appearance, and human factors engineering are important design activities. For the computer hardware designer, on the other hand, the component mounted in the cabinet is usually the largest system. Functional design efforts ensure that the various components (i.e., boxes) that make up a