🚀 go-pugleaf

In article <ASM370%90032315491404@EB0UB011>, orhan <PROHVK38@TREARN.BITNET>
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