1. Electrochemical Battery Impedance
Lithium-ion cells chemically degrade with each cycle. Solid Electrolyte Interphase (SEI) layer growth increases internal resistance ($R_{int}$).
When a high-power burst demands 4.5A peak current, Ohm's law dictates voltage drop across the internal cell: $\Delta V = I \cdot R_{int}$. If rail voltage dips below 3.35V, the Power Management IC faces an immediate emergency kernel panic (sudden shutdown). To prevent this, the OS proactively reduces CPU clocks.
V_rail = V_open - (I_peak × R_int)
2. NAND Flash SLC Cache & Garbage Collection
Modern UFS and NVMe storage use TLC/QLC flash with a fast pseudo-SLC cache. When your phone exceeds 80–85% storage capacity, this cache shrinks or vanishes.
Every subsequent write or app launch requires immediate block-level erase cycles (Garbage Collection) before new pages can be written. The CPU thread stalls waiting on synchronous I/O, manifesting as stuttering frame drops and app freezing.
IOPS_drop = f(WAF, Block_Clean_Ratio)
3. Software Inflation (Wirth's Law)
"Software is getting slower more rapidly than hardware becomes faster." Over 2 to 3 years, apps update with newer SDKs, heavier telemetry, cross-platform runtimes, and background AI daemons.
RAM occupancy increases, triggering low-memory killer (LMK) memory thrashing where background applications are repeatedly purged and cold-reloaded from slower storage.
RAM_Resident = Base_OS + (Daemons × Version)