IBM 1311

The IBM 1311 Disk Storage Drive was announced on October 11, 1962 and was designed for use with several medium-scale business and scientific computers. The 1311 was about the size and shape of a top-loading washing machine and stored 2 million characters on a removable IBM 1316 disk pack.Seven models of the 1311 were introduced during the 1960s. They were withdrawn during the early 1970s.
Models of the 1311 disk drive:

1. Had to be drive 1 on an IBM 1440, IBM 1460, or IBM 1240 system. Contained the controller and could control up to 4 – Model 2 drives. Introduced October 11, 1962. Withdrawn February 8, 1971.
2. Slave drive. Could have any special feature incorporated that the master drive (drive 1) had incorporated. Introduced October 11, 1962. Withdrawn January 6, 1975.
3. Had to be drive 1 on an IBM 1620 or IBM 1710 system. Contained the controller and could control up to 3 – Model 2 drives. Did not support any special features. Introduced October 11, 1962. Withdrawn May 12, 1971.
4. Had to be drive 1 on an IBM 1401 system. Contains the controller and can control up to 4 – Model 2 drives. Introduced October 11, 1962. Withdrawn February 8, 1971.
5. Had to be drive 1 on an IBM 1410, IBM 7010, or IBM 7740 system. Contained the controller and could control up to 4 – Model 2 drives. Direct Seek came as standard on this model. Introduced January 7, 1963. Withdrawn May 12, 1971.
6. No information available, probably a master drive (drive 1). Introduced March 5, 1968. Withdrawn February 2, 1971.
7. No information available, probably a master drive (drive 1). Introduced March 5, 1968. Withdrawn February 2, 1971.

The optional special features were

• Direct Seek: Without this option every seek returned to track zero first.
• Scan Disk: Automatic rapid search for identifier or condition.
• Seek Overlap: Allowed a seek to overlap ONE read or write and any number of other seeks.
• Track Record: Increased the capacity of the disk by writing ONE large record per track instead of using sectors.

Drive 1 (the master drive: models 1, 3, 4, and 5) was about a foot wider than the other drives (the slave drives: model 2), to contain extra power supplies and the control logic.
Each IBM 1316 Disk Pack was 4 inches (100 mm) high, weighed 10 pounds (4.5 kg) and contained six 14-inch (360 mm) diameter disks, yielding 10 recording surfaces (the outer surfaces were not used). The 10 individual read/write heads were mounted on a common actuator within the disk drive which was moved in and out hydraulically and mechanically detented at the desired track before reading or writing occurred. The disks spun at 1500 rpm. Each recording surface had 100 tracks with 20 sectors per track. Each sector stored 100 characters. The disk pack was covered with a clear plastic shell and a bottom cover when not in use. A lifting handle in the top center of the cover was rotated to release the bottom cover. Then the top of the 1311 drive was opened and the plastic shell lowered into the disk-drive opening (assuming it was empty). The handle was turned again to lock the disks in place and release the plastic shell, which was then removed and the drive cover closed. The process was reversed to remove a disk pack.