As eMMC flash memory ages, cells degrade and "bad blocks" appear. When the controller encounters these bad blocks, it has to work harder to manage error correction code (ECC) and remap data to healthy sectors. This increased workload generates excess heat.
A known erratum in the POSTAL3 bootloader (U-Boot 2017.09 variant) can send the eMMC into a continuous command retry loop. The chip never enters sleep mode. Result? Constant 0.5W dissipation in a 6mm x 8mm package—enough to hit 70°C. postal3 emmc hot
Budget devices often use older or lower-binned eMMC standards (e.g., eMMC 5.0 or 5.1). These have lower write efficiency compared to modern UFS or NVMe, leading to longer active times and more heat generation during data transfers. As eMMC flash memory ages, cells degrade and