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QIC Tape Drives

This section provides information useful to administrators of systems with 1/4-inch cartridge (QIC) tape drives.

The following terms are defined for QIC tapes:

QIC

Quarter-inch cartridge.

QIC-02

Host interface standard.

QIC11

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

QIC24

Recording format: 9 tracks with a typical track width of .0135 inch. Density is 8,000 bpi. Typical capacity is 60 MB with 6.6 MB per track.

QIC120

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.

QIC150

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

Note: It is important to use actual QIC designations here because many low-density drives can write (and read) in both QIC24 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 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 correct format 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.

When you first try to read a tape written on a QIC24 drive on a QIC150 drive you will often hear a noise caused by the drive switching modes and trying different possibilities to determine how the tape was written, because it does not 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 that the QIC150 has tighter mechanical tolerances. About the only visible difference is that the pinch roller (next to the rubber drive roller) in the QIC150 has a guide slot milled into it, and the 600A does not.

The following tables show read/write compatibility for low-density and high-density QIC tape drives with differing patterns of data blocks (formats).

Low-Density QIC Tape Drive Compatibility
Tapes Read Write
LD tapes formatted in LDF Yes Yes
LD tapes formatted in HDF Process not recommendedProcess not recommended
HD tapes formatted in LDFYesYes
HD tapes formatted in LDF assuming LDF is QIC24YesYes
HD tapes formatted in HDFNoYes (rewrite to LDF)

High-Density QIC Tape Drive Compatibility
TapesRead Write
HD tapes formatted in LDFYes No
LD tapes formatted in HDFProcess not recommendedProcess not recommended
HD Tapes formatted in LDFYesYes
HD tapes formatted in LDF assuming LDF is QIC24YesNo
HD tapes formatted in HDFYesYes

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

Refer to your tape drive documentation for more information.



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