《Low Power Design Essential》读后笔记(一)

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chapter 1

1. power and energy consumption

analyze the different application domains from power perspective

technology trends CMOS scaling

design solutions

2. key words: power dissipation

data center needs air conditioning to remove the dissipated heat

cooling issue processors closer to the floor operate faster than the ones on the top

SoC (Systems-on-a-chip) temperature gradients

higher temperature means slower clock speed.

3. key words: emergence of mobile electronics

battery-operated device available energy is fixed

improved electrode structures, better charging technology, advanced battery system design

4. categories

“Watt nodes” $P>1W$

“Milliwatt nodes” $1mW<P<1W$

“Microwatt nodes” $P<1mW$

5. Energy scavenging

to transform the physical energy present in various sources in the environment into electrical power.

6. average power dissipation & peak power dissipation

average power dissipation: when studying heat-removal and packaging concerns of high-performance processors

peak power dissipation: when designing the complex power supply delivery networks for integrated circuits and systems

7. power trends

up to mid 1990s: the average power dissipation of a processor rose by a factor of four every three years.

after: approximately a factor of 1.4 every three years.

Reason: abandoned the idea of a supply voltage fixed at 5 V.

power density instead of power independent of the actual die size

8. under fixed-voltage scaling and long-channel devices

$k$ is the technology scaling factor

clock frequency $f$ scales between technology generations as $k^2$

power density: $$p=C{V_{DD}}^{2}f$$ $$k_p=k\times 1\times k^2=k^3$$

under full-scaling mode

clock frequency scales as $k^{1.7}$. $$k_p=k\times (1/k{)}^2\times k^{1.7}=k^{0.7}$$

9. leakage might ruin Moore’s Law

classic wisdom dictates that power densities above 150 W/$c{m}^2$ should be avoided

computing density (computations per unit area and time) : $k^3$

dynamic power density : $k^{1.9}$

static power density (leakage power density): $k^{2.7}$

11. distribution of power: computation, memory, clock, and interconnect
    “power management”

12. an era of power-limited scaling