Memory downsizing in a computer memory subsystem

Memory downsizing in a computer memory subsystem, the subsystem including one or more channels of computer memory with each channel including several Dual In-line Memory Modules ('DIMMs') and each DIMM capable of on-die termination ('ODT'). Memory downsizing according to embodiments of the present invention includes identifying, during a memory initialization test in a Power On Self Test ('POST') by a firmware module, a defective DIMM of a particular channel in the computer memory subsystem and disabling, by the firmware module, the defective DIMM, including enabling ODT for the defective DIMM without disabling any non-defective DIMMs.