Foundations — Energy efficiency (performance per watt)

6.4.10 · D1 · Hardware › Power, Thermal & Reliability › Energy efficiency (performance per watt)

Is page pe assume kiya gaya hai ki tumne kuch bhi nahi dekha. Hum har letter aur picture ko parent note pe use hone se pehle naam dete hain, ek aisi order mein jahan har idea usse pehle wale idea pe tikta ho.

1. Energy, Power, Work, aur Joule

Kisi bhi chip ki baat se pehle, teen seedhe words.

Ye topic kyun zaroori hai: performance/watt mein work ko power se divide karte hain. "Work per second" aur "energy per second" ke andar ke seconds cancel ho jaate hain, aur bacha rehta hai work per joule. Ye cancellation tab tak nahi dikhega jab tak pata na ho ki power literally joules ÷ seconds hai. Hum "work" side ko kaise count karte hain, iske liye dekho FLOPS and Benchmarking.

2. Transistor as a switch, aur capacitor $C$

Ye topic kyun zaroori hai: parent ki headline equation $P_{\text{dyn}}=\alpha C{V}^{2}f$ mein $C$ hai. Yeh jaane bina ki $C$ "charge held per volt" hai, baad mein $V^2$ ek mystery rahega.

3. Voltage $V$ aur capacitor pe stored energy

Ye topic kyun zaroori hai: parent ka sabse bada "aha" moment — voltage aadha karne se dynamic power quarter ho jaati hai — yahi triangle area ek quarter ho jaana hai. Yahi engine hai DVFS - Dynamic Voltage and Frequency Scaling ke peeche bhi.

4. Frequency $f$ aur activity factor $\alpha$

Ye topic kyun zaroori hai: $\alpha$ ke bina hum assume karte ki saare gates har tick pe switch karte hain aur power hugely over-estimate ho jaata. $\alpha$ ki wajah se real chips apne worst case se kaafi kam draw karti hain.

5. Dynamic power law assemble karna

Ab har letter define ho chuka hai, toh parent ki boxed equation ek sentence ki tarah padhti hai:

Isko parent pe fully derive kiya gaya hai; ab tumhare paas wo har symbol hai jo wo use karta hai. Is switching drain ko hamesha-on drain se compare karo jo hai Dynamic vs Static Power mein.

6. Leakage current $I_{\text{leak}}$ aur static power

Ye topic kyun zaroori hai: total power hai $P_{\text{dynamic}}+P_{\text{static}}$. Parent pe teesri "common mistake" poori tarah is term ko bhoolne ke baare mein hai.

7. Wo chain jo efficiency collapse karti hai ($V\propto f$)

$V\propto f$ ko $P_{\text{dyn}}=\alpha C{V}^{2}f$ mein substitute karne se $V^{2}f$ ban jaata hai $f^2\cdot f=f^3$. Performance sirf $f$ ki tarah badhti hai, toh: $\frac{\text{Perf}}{\text{Watt}}\propto \frac{f}{f^3}=\frac{1}{f^2}$ Woh $1/f^2$ decline hi wajah hai ki designers ne clock speed chase karna band kiya aur kaam ko kai cores mein spread kiya — dekho Multicore and Parallelism aur budgeting number Thermal Design Power (TDP).

8. Metric pe do units padhna

Prerequisite map

Equipment checklist

Khud test karo — right side cover karo.