Xref: utzoo bit.listserv.asm370:3 comp.lang.asm370:432 Path: utzoo!attcan!uunet!samsung!psuvax1!psuvm!AUVM!JIM From: JIM@AUVM.BITNET (Jim McIntosh) Newsgroups: bit.listserv.asm370,comp.lang.asm370 Subject: Re: IPL Message-ID: <90085.092308JIM@AUVM.BITNET> Date: 26 Mar 90 14:23:08 GMT References: Sender: IBM 370 Assembly Programming Discussion List Reply-To: IBM 370 Assembly Programming Discussion List Organization: The American University - University Computing Center Lines: 27 Approved: NETNEWS@PSUVM.BITNET Gateway In article , orhan says: > Does anybody know IPL RECORD format ? Sure. Refer to pages 4-35 through 4-37 in the System/370 Principles of Operation (GA22-7000), or equivelent pages in the XA or ESA POOs, for a good overview of what happens during an IPL. Basically, a read with a length of 24 is issued. An initial PSW (0-7) and two additional CCWs (8-15 and 16-23) are read to address 0. This initial read is done as if the command chain bit is on, and control is chained to the CCW at address 8. Usually this first CCW would read in some more CCWs and the second CCW would TIC to them. When the initial I/O operation completes, the PSW at address 0 is loaded and you're on your way. (Note that this initial PSW can be part of the IPL record, or it can be placed at address 0 by a subsequent CCW.) So the IPL record format is: +--------+--------+--------+-----------... | PSW | CCW1 | CCW2 | Ignored +--------+--------+--------+-----------... 0 8 16 24 ------- Jim McIntosh (JIM@AUVM) The American University Washington DC 20016 USA