What makes memory compatible? For purposes of this document, compatibility is defined as functional equivalency. The minimum requirements for functional equivalency are size, speed and configuration. If any of these three parameters differ between two DIMMs, then the DIMMs are incompatible. For example, a 2GB memory module built with 1GB parts is not compatible with a 2GB memory module built with 512MB parts. In addition, a PC2100 DIMM is not compatible with a PC2700 DIMM, even if size and configuration are the same.