IBM 729 the tape reel. A 3/4 inch gap between records allowed the mechanism enough time to stop the tape. Initial tape speed was 75 inches per second (2.95 m/s) and recording density was 200 characters per inch, giving a transfer speed of 120 kbit/s. Later 729 models supported 556 and 800 characters/inch (transfer speed 480 kbit/s). At 200 characters per inch, a single 2400 foot tape could store the equivalent of some 50,000 punched cards (about 4,000,000 six-bit bytes, or 3 MByte). The 729 series was superseded by 9 track tape drives introduced with the IBM System/360. The IBM 729 I
Magic cube classes was first constructed in late 2004 by Mitsutoshi Nakamura. This cube is a combination Pantriagonal magic cube and Diagonal magic cube. Therefore, all main and broken triagonals sum correctly, and it contains 3"m" planar simple magic squares. In addition, all 6 oblique squares are pandiagonal magic squares. The only such cube constructed so far is order 8. It is not known what other orders are possible. See Pantriagdiag magic cube. Minimum correct summations required = 7"m" + 6"m" ALL 3"m" planar arrays must be pandiagonal magic squares. The 6 oblique squares are always magic (usually simple magic). Several of them