 A non-removable media variant family of 12, 24 and 48 MB capacity, the MMD, was then announced in 1976.This family's interface, SMD, derived from the earlier Digital RP0x interface, was documented as ANSI Standard X3.91M - 1982, Storage Module Interfaces with Extensions for Enhanced Storage Module Interfaces.The SMD interface is based upon a definition of two flat interface cables ("A" control and "B" data) which run from the disk drive to a controller and then to a computer.