Photographs of computer tapes; tape specifications
media and data conversion services by Disc Interchange


Of all the computer tapes in use today, these tapes seem to be the most confusing to our customers, mostly due to the wide variety and the many name changes over the years. 
So we have written detailed notes about these tape, and we present several tables of information below.

Tape names:


Drive names:


Photo: Generic tape
Size: 6.0"W X 4.0"H X 0.60"T
Tape types: Many types of media in this case style.
Notes: There are many tapes in this series. Early tapes were called QIC tapes (pronounced "quick"), later tapes were called MLR, and current tapes are called SLR:
QIC = Quarter Inch Cartridge
MLR = Multi-channel Linear Recording
SLR = Scalable Linear Recording
Most of the QIC and both MLR drives have been given new SLR designations. See the table immediately below.
Tapes in the QIC series are generally marked "DC" media. Tapes in the MLR series are marked "MLR", and tapes in the current SLR series are marked "SLR".
Some tape manufacturers used prefixes other than DC, so you may see MC, QD, DL, etc.  Imation (3M) calls their tapes "Magnus".  All products introduced in the last few years are called SLR.

DC-600, DC-6000, DC-9000, Magnus, MLR, SLR tape

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Drive Equivalences

Old designation New designation
QIC-150 SLR-1
QIC-525 SLR-2
QIC-1000 SLR-3
SLR-6 SLR-24
MLR-1 SLR-32
MLR-3 SLR-50
Notes about SLR media and formats
  1. These tapes can be identified by their size and by the solid aluminum backing plate. The early tapes are called "Quarter Inch Cartridge tapes", or "QIC tapes" (pronounced "quick"), while current tapes are called SLR.  MLR tapes, which existed briefly, have been renamed to SLR. 

  3. There are many different types of media with different coercivities and number of tracks.  All DC and MLR tapes are 0.250" wide.  Some SLR are 0.250" wide, but most newer SLR tapes are 0.315" wide. The number of tracks range from 4 to 192 (plus servo tracks).  Capacity (as of 2006) ranges from 2 MB to 140 GB. See the table below. 

  5. Historically, the product numbers have meant different things.  The DC-300 and DC-600 tapes were 300' and 600' long, respectively.  After the DC-xxx tapes came DC-6xxx, where the xxx denotes the capacity in MB,  then DC-9xxx, where the xxx denotes the capacity in tens of MB (e.g., a DC-6150 is a 150 MB tape, and a DC-9250 is a 2500 MB tape).  Imation (3M) calls their tapes "Magnus", and some manufacturers use prefixes other then DC. 

  7. There was briefly a series called MLR.  Those have now been renamed SLR.  The MLR-1 is now the SLR-32 and the MLR-3 is now the SLR-50.

  9. The entire series of drives from the QIC-150 up have now been renamed to SLR.  SLR-1 is the new designation for DC-6150, SLR-2 is the new designation for DC-6525, etc.   This makes the naming of the entire product line more consistent than it was.  SLR-1 through SLR-7 are merely sequential product numbers in the series.  Beginning with SLR-24, the number indicates the compressed tape capacity in GB.  These equivalences are listed in the table below.

  11. The MLR-1, MLR-3, SLR-6, and SLR-24 through SLR-140 tapes contain factory-written servo tracks, and therefore cannot be degaussed (bulk erased).  If you degauss one of these tapes, it will destroy the tape for further use.

  13. These tapes are not pre-formatted (like the mini-cartridges), and the QIC standards do not specify the file structure on the tape, only the physical recording characteristics.  The software or user is free to write any file structure to the tape.

  15. There are two types of QIC drives.  Some older drives can only record blocks of 512 bytes in size.  This was particularly true of the QIC-11 and QIC-24 tapes, and very common with the early QIC-150 drives.  Most QIC-120 and QIC-150 drives, and all QIC-525 drives and above can operate in Variable Block mode, and record blocks of variable size.  Those drives can be used much like a 9-track or 3480 tape, recording similar file structures. This difference is the primary determining factor in which file structures can be written on a given QIC drive. 

  17. QIC-24 was the first format to adhere to a QIC standard, where the tapes could be interchanged between drives and computers of different manufactuers. Many of the QIC-11 formats, and all drives before QIC-11 were generally specific to the manufacturer, and those tapes could not be read in another manufacturer's drive.

  19. Tandberg is the major manufacturer of SLR drives, and generally sets the standards for the drives. Other manufacturers may make a similar product with slightly different specifications. For example, the maximum block size a drive can handle varies by manufacturer, even for the same drive type, such as SLR-4.

  21. Most PC backup programs write proprietary formats to fixed block QIC tapes, either because the drive only supports fixed block recording, or because fixed block recording is faster and more efficient than variable block recording.  UNIX systems commonly write tar and cpio, usually to fixed block tapes. IBM AS-400 writes Standard-Label tapes in variable block mode.  There are many other formats, too.


Media / Drive Compatibility Table

<---- Tape Drives ---->
SLR40 SLR50 
SLR60 SLR75 SLR100 SLR140
SLR140 R/W
SLR100 R/W R/W
SLR40 R/W x R/W R/W R/W R/W
SLR7 R/W R x R R R R
SLR32/MLR1 x R/W R R/W R R R x
SLR6/24 R/W x R/W R R R/W (1) R R R x
SLR5 R/W R R R R/W R R R R x x
SLR4 R/W R/W R x R R/W x R R R x x
SLR3 R/W R/W R/W x x x x x x x x x x
SLR2 R/W R/W R/W R/W x x x x x x x x x x
SLR1 R/W R/W R/W R/W x x x x x x x x x x x

Blank or x = Can't read or write.       R = This drive reads this tape.       R/W = This drive reads and writes this tape.       R/W = Native format for this drive.

More photographs of tapes

QIC / DC / MLR / SLR media table:

QIC = Quarter-Inch Cartridge
MLR = Multi-channel Linear Recording
SLR = Scalable Linear Recording


  1. Some manufacturers use a prefix other than DC. For example, Maxell uses MC, Sony uses QD, Verbatim uses DL, and 3M calls their tapes "Magnus".
  2. There are more tape types than listed here.  Many of the SLR tapes have short and long versions not listed here, and there were other less-common DC tapes.
  3. DISC can convert most QIC / MLR / SLR tapes, including many not listed below.
  4. The table below is ordered by media designation (e.g. DC-6150), then by recording format.
Media Recording Format Width Length, feet Capacity
(native / compressed)
Comments Notes
DC-300 QIC-11, 24 .25 300 2.5 - 30 MB See note 1 about formats 1, 2
DC-300XL QIC-11, 24 .25 450 4 - 45 MB Extra-length DC-300 1, 2
DC-600 QIC-11 .25 600 8-60 MB Rarely found 1, 2
DC-600A QIC-24 .25 600 60 MB Most common QIC format 2
DC-600A QIC-120 .25 600 120 MB   3
DC-600A/XL QIC-24 .25 1020 100 MB Extra-length DC-600 2
DC-600AXL QIC-120 .25 1020 200 MB Extra-length DC-600 3
DC-615A QIC-24 .25 150 15 MB Short DC-600 2
DC-615A QIC-120 .25 150 30 MB Short DC-600 3
DC-6037 QIC-120 .25 150 29 MB Short DC-6150 3
DC-6037 QIC-150 .25 150 37 MB Short DC-6150 3
DC-6150 QIC-120 .25 620 120 MB Common on AS/400 3
DC-6150 QIC-150 .25 620 150 MB Now SLR-1 3, 4
DC-6250 QIC-120 .25 1020 200 MB Extra-length DC-6150 3
DC-6250 QIC-150 .25 1020 250 MB Extra-length DC-6150 3
DC-6320 QIC-525 .25 620 320 MB Short DC-6525  
DC-6525 QIC-525 .25 1020 525 MB Now SLR-2 4
(Magnus 1.0)
QIC-1000 .25 760 1 GB    
(Magnus 1.2)
QIC-1000 .25 950 1.2 GB Now SLR-3 4
DC-9135 QIC-1350 .25 760 1.35 GB    
DC-9150 QIC-1000 .25 1200 1.5 GB    
DC-9165 QIC-1350 .25 950 1.65 GB    
(Magnus 2.0)
QIC-2GB, 2GB-DC .25 950 2 / 4 GB    
(Magnus 2.1)
QIC-2GB, 2GB-DC .25 1020 2.1 / 4.2 GB    
(Magnus 2.5)
QIC-2GB, 2GB-DC .25 1200 2.5 / 5 GB Now SLR-4 4
DC-9265 QIC-2100c .25 1200 2.65 GB    
MLR1 QIC-5010 .25 187 2 / 4 GB Short tape  
MLR1 QIC-5010 .25 1200 13 / 26 GB    
MLR1 QIC-5010 .25 1500 16 / 32 GB Now SLR-32  
MLR3 MLR-3 .25 1515 25 / 50 GB Now SLR-50  
SLR1 QIC-150 .25 620 150 MB    
SLR2 QIC-525 .25 1050 525 MB    
SLR3 QIC-1000 .25 950 1 GB    
SLR4 QIC-2GB, 2GB-DC .25 1200 2.5 / 5 GB    
SLR5 QIC-4GB, 4GB-DC .25 1500 4 / 8 GB    
SLR6 SLR-6 .25 1125 12 GB Renamed to SLR-24 5
SLR7 SLR-7 .315 1545 20 / 40 GB   5
SLR24 SLR24 .25 1130 12 / 24 GB   5
SLR32 QIC-5010 .25 1500 16 / 32 GB   5
SLR40 ALRF-1 .315 615 20 / 40 GB   5
SLR50 MLR-3 .25 1500 25 / 50 GB   5
SLR60 ALRF-1 .315 915 30 / 60 GB   5
SLR75 ALRF-1 .315 1150 37.5 / 75 GB   5
SLR100 ALRF-1 .315 1500 50 / 100 GB   5
SLR140 ALRF-6 .315 1660 70 / 140 GB   5
  1. DC-300 tapes may contain QIC-11 4 track, QIC-11 9-track, QIC-24 9-track, or a proprietary format.  DC-600 tapes occasionally contain QIC-11, but the vast majority are QIC-24. 
  2. These formats were always recorded in 512 byte fixed-block mode.
  3. These tapes were most often recorded in 512 byte fixed-block mode, but some drives could operate in variable block mode. 
  4. Recently re-designated SLR. 
  5. These tapes may also come in short or long versions. 

Table Copyright 2006-2015 by Disc Interchange Service Company, Inc.
All rights reserved.
Reproduction of this table is NOT permitted.

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