◀ Back to Note

Tony's Intertwingled Memex • Reference Manual

Processor Thermal Power Dissipation (Computer & Electrical Engineering)

Formulas & Definitions

In modern computer microchip architecture, the local dynamic thermal power dissipation PPP (in milliwatts, mW\text{mW}mW) of a processing core transistor sub-grid depends on its clock frequency fff (in gigahertz, GHz\text{GHz}GHz) and logic supply voltage VVV (in volts, V\text{V}V), governed by:

P(f,V)=12fV2P(f, V) = 12fV^2P(f,V)=12fV2

To handle a demanding computational workload spike, an embedded Dynamic Voltage and Frequency Scaling (DVFS) microcontroller algorithm adjusts both operational parameters concurrently over run-time ttt (in milliseconds, ms\text{ms}ms):

  • f(t)=2+ln⁡(t+1)f(t) = 2 + \ln(t + 1)f(t)=2+ln(t+1)
  • V(t)=1.0+0.05t2V(t) = 1.0 + 0.05t^2V(t)=1.0+0.05t2
  1. Compute the operating frequency f(1)f(1)f(1) and voltage V(1)V(1)V(1) at t=1 mst = 1\text{ ms}t=1 ms.
  2. State the multivariable chain rule formula for the total time derivative dPdt\frac{dP}{dt}dtdP​.
  3. Calculate the instantaneous rate of change of power dissipation dPdt\frac{dP}{dt}dtdP​ at t=1 mst = 1\text{ ms}t=1 ms.
  4. Explain how modern thermal management firmware uses the partial sensitivities ∂P∂f\frac{\partial P}{\partial f}∂f∂P​ and ∂P∂V\frac{\partial P}{\partial V}∂V∂P​ to prevent processor thermal throttling.