3B Tape Drive Info

3B Tape Drive Info

3b2-Tape-Drives.txt

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+Edited 1-13-2024
+
+There have been two major families of cartridge tapes on the 3B2 family,
+and they are not at all interchangeable. We'll describe them here in
+case you're sorting through what's in front of you.
+
+23MB Cartridge Tape Drive Model 3b2-400
+
+The first tape drive available for the 3B2 family was the 23 megabyte 
+Cartridge Tape Drive, and these are not compatible with any of the 
+later SCSI drives. It was standard equipment on the 3B2/400 and was 
+available in the XM expansion module for the 3B2/300, /310 and the /400. 
+As far as we know, the 3B2 is the only system that can read these tapes.
+
+These units use the CTC driver and are accessed via the device 
+/dev/rSA/ctape1. There is a special ctccpio command that is able to put 
+the device into streaming mode, but we've seen enough problems with 
+this command that we prefer to use the standard cpio command for this 
+even though it's a bit slower. A noticeable feature of the non-streaming 
+mode is the very annoying back-and-forth running of the tape while 
+reading: we've heard it described as "wheezing".
+
+A particular oddity of these tape drives is that because they "look" 
+like a (very large) floppy disk drive, the drive provides a block device 
+interface (/dev/SA/ctape1), in addition to the expected character 
+(aka "raw") device interface (/dev/rSA/ctape1. This means that it's 
+possible to mount a tape drive as a filesystem. It works, but it's so 
+slow that it's hard to convey just how painful this is.
+
+Our particular unit is a Cipher FloppyTape 525 (model 960273), and it is 
+branded with AT&T part number KS-23165. It uses a floppy disk interface 
+with the familiar 34 pin card-edge connector as found on older 5-1/4" 
+floppy drives. A distinguishing mark of this drive is the flip-up lever 
+that is used to engage the tape after insertion: most of the drives 
+shipped with the 3B2 were of this type. We understand that there is also 
+a similar drive made by Wangtek that looks very much like the SCSI units.
+
+Our understanding of these drives is that they should not use the same 
+DC600 cartridge tapes as do the 60 and 120 MB SCSI drives, but after 
+recently reviewing the 3B2 service documentation we are no longer of 
+this view: AT&T says that DC600 tapes can be use in all their drives. 
+This is good news: we've been telling people for 10 years that they have 
+to use special tapes. Oh well.
+
+It is possible to add a 23 MB tape drive to the 3B2/600 and newer units: 
+we simply install the CTC I/O card (CM195H) into the 3B2/600 and install 
+the CTC driver. We've done this on our system, though the mechanical 
+arrangements are "suboptimal". Because the 23MB drive doesn't really have 
+any provisions for external cabling. the only real way to do this is to 
+mount the 23MB unit inside the cabinet and put the displaced SCSI tape 
+drive into an external case: then use "regular" external SCSI cables to 
+connect them.
+
+This "floppy tape" interface is used in other computer systems, including 
+many on the PC. As such, the Linux floppy tape project might prove fruitful 
+for those determined to read and write many tapes on their own systems. 
+We are not even close to motivated enough to try this ourselves, but we'd 
+surely love to report on the experiences of others.
+
+60/120MB SCSI Tape Drives Model 3b2-700
+
+The 3B2/600 and later models (including the low-profile /522) all came with 
+SCSI tape drives of either 60 or 120 megabyte capacity, and these are 
+standard units as found in many other pieces of equipment.
+
+We believe that AT&T only used Wangtek drives, and they are of the type 
+where you push the tape in, hear a click, and let go: now the drive is 
+engaged. To release, just push again and the tape pops out. The drives 
+from AT&T have a small "60" or "120" stamped on the faceplate to report 
+the capacity.
+
+These drives all use the ST01 driver, and the device name is /dev/rSA/qtape1. 
+Not surprisingly, there is no block device.
+
+A 120 MB drive can read a 60 megabyte tape but cannot write one. Neither 
+of these drives can read or wrote the 23 MB format. Sorry.
+
+
+
+From Steve Friedl's 3B2 Tech Tips unixwiz.net/3b2/tapedrives.html
+