IBM 728

The IBM 728 magnetic tape drive was used on the SAGE AN/FSQ-7 computer. It was physically similar to the IBM 727, but with significantly different specifications.

This is one of several IBM 7 track tape drives.

tracks	6 Data, 1 synchronization
char/inch	248 char/inch
words	6 chars (32 data bits, 1 odd parity bit, 3 end of file bits)
word/inch	41.33 word/inch
end of record gap	0.75 inch - 186 chars - 31 words
Tape speed	75 inch/s
Rewind speed	500 inch/s (average)
Transfer rate	18,750 char/s - 3,125 word/s
Start time	5 ms
Stop time	5 ms
Width of tape	1/2 inch
Length of reel	2,400 ft (730 m)
Composition	Mylar or cellulose acetate base

            Tape Word Bit Positions
 
            ----------------------------->   Tape travel
            LS   L6   L12  R2   R8   R14
            L1   L7   L13  R3   R9   R15
            L2   L8   L14  R4   R10  P
            SYN  SYN  SYN  SYN  SYN  SYN
            L3   L9   L15  R5   R11  EOF
            L4   L10  RS   R6   R12  EOF
            L5   L11  R1   R7   R13  EOF
            ----------------------------->   Tape travel

Magnetic tape data storage formats

Linear

Wide (19 - 25.4 mm)	TX-2 Tape System (1958) IBM 7340 (1961) LINCtape (1962) DECtape (1963)

Half inch (12.7 mm)	UNISERVO (1951) IBM 7 track (1952) 9 track (1964) IBM 3480 (1984) DLT (1984) IBM 3590 (1995) T9840 (1998) T9940 (2000) LTO Ultrium (2000) IBM 3592 (2003) T10000 (2006)

Eight millimeter (8 mm)	Travan (1995) IBM 3570 MP (1997) ADR (1999)

Quarter inch (6.35 mm)	QIC (1972) SLR (1986) Ditto (1992)

"Eighth" (0.15) inch (3.81 mm)	KC standard, Compact Cassette (1975) HP DC100 (1976) Tarbell Cassette Interface (1976) Commodore Datasette (1977) DECtape II (1979)

Stringy (1.58–1.9 mm)	Exatron Stringy Floppy (1979) ZX Microdrive (1983) Rotronics Wafadrive (1984)

Helical

Three quarter inch (19 mm)	Sony DIR (19xx) Ampex DST (1992)

Half inch (12.7 mm)	Redwood SD-3 (1995) DTF (19xx) SAIT (2003)

Eight millimeter (8 mm)	Data8 (1987) Mammoth (1994) AIT (1996) VXA (1999)

Four millimeter (3.81 mm)	DDS/DAT (1989)

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