Top-loading single platter drives are descendants of the IBM 5440 series used on the System 3, which were copied by most of the players in the day (Pertec, Wanco, Western Dynex, Diablo, etc.). DEC used the case design for the RL01/2 but added an embedded servo track. 2314s are 20 surface top loading 'washing machine' drives. End of the line for the head technology started on the 1311 (10 surface). Had the chance last week to talk to one of the guys at Memorex who did their early 2314 clones in the late 60's (sold to DEC as the RP01 and RP02).