QIC Tape Drives

The following terms are defined for QIC tapes:

QIC

Quarter-inch cartridge.

QIC-02

Host interface standard.

QIC-11

Recording format. Used on Sun Workstations with 60 MB drives. Cannot be read on Silicon Graphics systems.

QIC-24

Recording format: 9 tracks with a typical track width of .0135 inch. Density is 8000 bpi. Typical capacity is 60 MB with 6.6 MB per track.

QIC-120

Recording format: 15 tracks with a typical track width of .0065 inch. Density is 10,000 bpi (NRZI Recording Mode). Typical capacity is 120 MB, with approximately 8+ MB per track.

QIC-150

Recording format used on current Silicon Graphics drives. Uses 18 tracks.

Note: It is important to use actual QIC designations here, since many low-density drives can write (and read) in both QIC 24 and QIC11. Typically, none of the QIC150 drives can read QIC11. QIC150 drives can write in both QIC150 (using DC6150 or DC600XTD; the name changed to the first), and in QIC120, if the tape is a 600A-style tape. Typically, QIC150 drives cannot write to QIC24.

Also note that the word format is misleading; there is no formatting on QIC tapes (some variants do require formatting, but Silicon Graphics does not support them). Format actually refers to the pattern of data blocks. Tapes have a cartridge type, and they are written in the format correct for that type. The type is determined by the hole pattern in the tape (preceding Beginning Of Tape, or BOT). Further, tapes written on QIC150 drives have a reference burst (magnetic pattern) written at the beginning of the drive.

The noise you often hear when you first try to read (on a QIC150 drive) a tape written on a QIC24 drive is the drive trying to figure out how the tape was written, by switching modes and retrying all the possibilities, if it doesn't see both a QIC150 cartridge and the reference burst. Physically, the noise you hear is the serve motor stepping the read/write head over each track.

The difference between a QIC150 and QIC120 (600A) cartridge is in the mechanical tolerances. The QIC150 has tighter tolerances. About the only visible difference is in the pinch roller (next to the rubber drive roller). The QIC150 has a guide slot milled into it, and the 600A does not.

Low-Density QIC Tape Drive Compatibility

Tapes	Read	Write
LD tapes formatted in LDF	Yes	Yes
LD tapes formatted in HDF	Process not recommended.	Process not recommended.
HD tapes formatted in LDF	Yes	Yes
HD tapes formatted in LDF assuming LDF is QIC 24	Yes	Yes
HD tapes formatted in HDF	No	Yes (rewrite to LDF)

High-Density QIC Tape Drive Compatibility

Tapes	Read	Write
HD tapes formatted in LDF	Yes	No
LD tapes formatted in HDF	Process not recommended.	Process not recommended.
HD Tapes formatted in LDF	Yes	Yes
HD tapes formatted in LDF assuming LDF is QIC 24	Yes	No
HD tapes formatted in HDF	Yes	Yes

Regarding read/write activity for a low-density tape formatted in high density, it is not only not recommended, it isn't even possible if the tape is a QIC24 (DC300XL or DC450XL) tape. If the tape is a QIC120 (DC600A) read/write does work correctly, and there is no reason to recommend against it.