of a Read IPL command, , with command chaining and suppress incorrect length indication being enforced). When the I/O channel commands are complete, the first group of eight bytes is then loaded into the processor's Program Status Word (PSW) and the startup program begins execution at the location designated by that PSW. The IPL device is usually a disk drive, hence the special significance of the read-type command, but exactly the same procedure is also used to IPL from other input-type devices, such as tape drives, or even card readers, in a device-independent manner, allowing, for example, the installation of an operating system on a brand-new computer from an OS initial distribution magnetic tape. For disk controllers, the command also causes the selected device to seek to cylinder , head , simulating a Seek cylinder and head command, , and to search for record , simulating a Search ID Equal command, ; seeks and searches are not simulated by tape and card controllers, as for these device classes a Read IPL command is simply a sequential read command. The disk, tape or card deck must contain a special program to load the actual operating system or standalone utility into main storage, and for this specific purpose "IPL Text" is placed on the disk by the stand-alone DASDI (Direct Access Storage Device Initialization) program or an equivalent program running under an operating system, e.g., ICKDSF, but IPL-able tapes and card decks are usually distributed with this "IPL Text" already present. IBM introduced some evolutionary changes in the IPL process, changing some details for System/370 Extended Architecture (S/370-XA) and later, and adding a new type of IPL for z/Architecture. Minicomputers Minicomputers, starting with the Digital Equipment Corporation (DEC) PDP-5 and PDP-8 (1965) simplified design by using the CPU to assist input and output operations. This saved cost but made booting more complicated than pressing a single button. Minicomputers typically had some way to toggle in short programs by manipulating an array of switches on the front panel. Since the early minicomputers used magnetic-core memory, which did not lose its information when power was off, these bootstrap loaders would remain in place unless they were erased. Erasure sometimes happened accidentally when a program bug caused a loop that overwrote all of memory. Other minicomputers with such simple form of booting include Hewlett-Packard's HP 2100 series (mid-1960s), the original Data General Nova (1969), and