Computer Noise in the 21st Century

The Silent Front
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For the period 1995 to 2005, the clock rates for these devices are anticipated to grow by factors of 3.2 and 2.9, respectively. The density data is specified for low cost, high volume microprocessors and for low volume ASICs. Over the same time period noted above, the growth factor for both types of ASICs is projected to be 8.5.

Based upon these projections, and with consideration of all other design drivers, the SIA report provides power dissipation estimates for high performance microprocessors and ASICs. This data is shown in Figures 4 and 5. Again using the period from 1995 to 2005, the dissipation growth factor for microprocessors is 1.8. The ASIC dissipation is expected to double between 1995 and 2001, and then remain flat.


Figure 4: Projected power dissipation values for high performance microprocessors.


Figure 5: Projected power dissipation values for high performance ASICs.

Printed Wiring Board Design
With regard to circuit board design, the primary dissipation drivers are similar to the chip drivers noted above. While there is a corresponding desire to use conventional cooling techniques and keep power consumption low, there are also similar pushes in terms of board throughput and circuit pack densities. These figures tend to be proprietary so industry data is scarce. Figure 6 contains current and projected density data for 11 different boards used in Lucent products. The ten-year growth rate factors for these products range from 3.2 to 9.9. Assuming that this data is generally representative, circuit pack densities are clearly rising at a rapid pace.


Figure 6: Actual and projected circuit pack densities for 90 printed wiring board designs.

Lucent has also collected board heat dissipation on 90 different board designs. The data is relatively flat from mid-1991 (i.e., the start date of the data set) until mid-1996. The average power dissipation over that period is 0.035 W/sq.cm. In contrast, some new designs are at 0.2 W/sq.cm., a 5.7 factor increase in dissipation.



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