Memory configurations definitely will not work when populating a motherboard with DIMMs?

Memory configurations will not work when populating a motherboard with DIMMs if the installed memory modules are incompatible in terms of speed, size, or type (e.g., mixing DDR3 with DDR4). Additionally, using different ranks or single-sided vs. double-sided DIMMs can lead to issues. It's also crucial to follow the motherboard's specifications regarding the maximum supported memory capacity and the recommended slot population order. Failure to adhere to these guidelines may result in system instability or failure to boot.