$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 The 1302 was withdrawn in February 1965. 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 is about the size and shape of a top-loading washing machine and stores 2 million characters (12,000,000 bits) (or, in so-called "Load Mode" on an IBM 1401, a sector can hold 90 7-bit characters, or 12,600,000 bits total ) on a removable IBM 1316 disk pack. Seven models of the 1311 were introduced during the 1960s. They were withdrawn during the early 1970s. Each IBM 1316 Disk Pack is high, weighs and contains six diameter disks, yielding 10 recording surfaces (the outer surfaces are not used). The 10 individual read/write heads are mounted on a common actuator within the disk drive which moves in and out hydraulically and is mechanically detented at the desired track before reading or writing occurs. The disks spin at 1500 rpm. Each recording surface has 100 tracks with 20 sectors per track. Each sector stores 100 characters. The disk pack is covered with a clear plastic shell and a bottom cover when not in use. A lifting handle in the top center of the cover is rotated to release the bottom cover. Then the top of the 1311 drive is opened and the plastic shell lowered into the disk-drive opening (assuming it is empty). The handle is turned again to lock the disks in place and release the plastic shell, which is then removed and the drive cover closed. The process is reversed to remove a disk pack. The same methods are used for many later disk packs. There are seven models of the 1311 disk drive. The first drive attached to a system is a "master drive" which contains the controller and can control a number of Model 2 "slave drives." Master drive on an IBM 1440, IBM 1460, or IBM 1240 system and can control up to four Model 2 drives. Introduced October 11, 1962. Withdrawn February 8, 1971. Slave drive to a master drive. Can have any special feature incorporated that the master drive has incorporated. Introduced October 11, 1962. Withdrawn