HP2648A tape drive capstans

Based on posts here and information at hpmuseum.net, it seems that the 2647A and 2649A had a programmable aspect to the equipment, while the other 264x terminals did not. hpmuseum.net describes the following models in this line: 2640A introduced 1975, base terminal 2644A introduced 1975, added two mini cartridge tape drives 2645A introduced 1976, replaced the 2644A, "most common" 2648A introduced 1977, added graphics capability 2649A introduced 1977, programmable w/out tape drives 2647A introduced 1978, BASIC programmable w/tape drives & graphics -- "The Direct3D Graphics Pipeline"-- code samples, sample chapter, FAQ: <http://www.xmission.com/~legalize/book/> Pilgrimage: Utah's annual demoparty <http://pilgrimage.scene.org>