> when power drops, and the voltage levels on the power
rails start drooping, DRAM tends to go insane and starts returning
garbage long before the DMA engine and the hard drive stops
functioning
That doesn't sound right. DRAM can keep its content for a few seconds without power - it's what make Cold boot attacks [1] possible. Also, DRAM has its own buck voltage regulators, usually with hefty inductors, capable of delivering power long after +5V and +12V started to drop.