IBM 1311 Disk Storage Drive

The IBM 2302 was the S/360 version of the 1302, with track formatting in accordance with S/360 DASD architecture rather than 7000 series architecture.

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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 They were withdrawn during the early 1970s.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 Withdrawn February 8, 1971.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 Withdrawn January 6, 1975.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 Withdrawn May 12, 1971.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 Withdrawn February 8, 1971.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 Withdrawn May 12, 1971.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 Withdrawn February 2, 1971.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 Withdrawn February 2, 1971.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.

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IBM 1302


The IBM 1302 Disk Storage Unit was introduced in September 1963. Improved recording quadrupled its capacity over that of the 1301, to 117 million 6-bit characters per module. Average access time was 165 ms and data could be transferred at 180 K characters/second, more than double the speed of the 1301. A second arm accessed a separate group of 250 tracks. As with the 1301, there was a Model 2 with twice the capacity. The IBM 1302 Model 1 leased for $5,600 per month or could be purchased for $252,000. Prices for the Model 2 were $7,900 per month or $355,500 to purchase. The IBM 7631 controller cost an additional $1,185 per month or $56,000 to purchase. The 1302 was withdrawn in February 1965.










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IBM 1301

The IBM 1301 Disk Storage Unit was announced on June 2, 1961. It was designed for use with the IBM 7000 series mainframe computers and the IBM 1410. The 1301 stored 28 million characters on a single module (25 million with the 1410). Each module had 20 large disks and 40 recording surfaces, with 250 tracks per surface. The 1301 Model 1 had one module, the Model 2 had two modules, stacked vertically. The disks spun at 1800 rpm. Data was transferred at 90,000 characters per second.
A major advance over the IBM 350 and IBM 1405 was the use of a separate arm and head for each recording surface, with all the arms moving in and out together like a big comb. This eliminated the time needed for the arm to pull the head out of one disk and move up or down to a new disk. Seeking the desired track was also faster since, with the new design, the head would usually be somewhere in the middle of the disk, not starting on the outer edge. Maximum access time was reduced to 180 milliseconds.
The 1301 also featured heads that were aerodynamically designed to fly over the surface of the disk on a thin layer of air. This allowed them to be much closer to the recording surface, which greatly improved performance.
The 1301 was connected to the computer via the IBM 7631 File Control. Different models of the 7631 allowed the 1301 to be used with a 1410 or 7000 series computer or shared between a 7000 and a 1410 or between two 7000's.
The IBM 1301 Model 1 leased for $2,100 per month or could be purchased for $115,500. Prices for the Model 2 were $3,500 per month or $185,000 to purchase. The IBM 7631 controller cost an additional $1,185 per month or $56,000 to purchase. All models were withdrawn in 1970.

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IBM 1405

The IBM 1405 Disk Storage Unit was announced by 1961 and was designed for use with the IBM 1401 series, medium scale business computers. The 1405 stored 10 million characters on a single module. Each module had 25 large disks, yielding 50 recording surfaces. The disks spun at 1200 rpm. The Model 1 had one module, the Model 2 had two modules, stacked vertically. Each recording surface had 200 tracks and 5 sectors per track. Data was read or recorded at 22,500 characters per second. A single arm moved in and out and up and down. Access time ranged from 100 to 800 milliseconds (Model 2).

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