Ages ago Acard, who're makers of popular SCSI-IDE adapters and controller chips, made a 5.25" half height device that could take up to four DDR2 DIMMs, connecte

Ages ago Acard, who're makers of popular SCSI-IDE adapters and controller chips, made a 5.25" half height device that could take up to four DDR2 DIMMs, connected to the host computer using SATA, and had options for a CF card and a battery. I'd use something like this for heavy disk I/O over an SSD any day. Plus, it lets you use memory that would otherwise likely go to waste. However, those were expensive back then and haven't gotten any cheaper, nor are there newer devices that I know about that'd take newer DIMM types. That'd be nice, though.