Choosing a memory IC for an embedded board

Memory on an embedded board is not one component. It is a set of jobs: code that must survive power loss, data that must be rewritten often, and a buffer that only has to be fast. Mixing those jobs in one chip is how products wear out or boot slowly. Separate them before you read a single density number. Non-volatile memory holds the program and the calibration. NOR flash still wins when the CPU fetches code directly, because it is random-read and simple to boot from. NAND and eMMC win on density and cost per bit, but they need a controller, wear leveling, and a boot ROM that understands them. EEPROM and FRAM sit in the middle for small records that update constantly: counters, calibration bytes, and event logs. FRAM costs more and essentially does not wear out. EEPROM is cheaper and has a finite write life you should calculate, not hope about. Volatile memory is the working set. SRAM is easy and low power, and it is what small microcontrollers already integrate. SDRAM and DDR are what a microprocessor needs for Linux, and they bring layout rules, a termination scheme, and a training sequence at boot. PSRAM is a compromise on some wireless modules: DRAM density with an SRAM-like bus. If the processor already has a memory controller, use it. Bit-banging a parallel bus on GPIO will not meet the timing the datasheet assumes. Interface and endurance close the choice. SPI and QSPI keep the pin count down and are fine until the execute-in-place bandwidth runs out. Parallel buses are wider and older. I2C is only for the small devices. Temperature grade and data retention at the high end of that grade matter more than the room-temperature endurance figure. For parts grouped by technology rather than by a single catalog page of memory, memory ICs are easier to compare when density, interface, and endurance are the three columns on the sheet: https://chipapex.com/memory-ic/ Count write cycles for the data that changes, and boot bandwidth for the code that does not. A part that is excellent at one of those is often a poor fit for the other.