IPL Use the IPL =ommand to simulate an initial program load function for a
virtual machine. The format of the 1PL command is: r I 101 I , , I L r , ,CLear , vaddr [cylno 1 I I (STOP] L oJ system name r , [PARM {p1 p2 ••• l] --, I I I I I _______________________J vaddr rcvlnol ICLEAR , rSTOPl vaddr
cvlno
CLEAR STOP syst emname
L .J
simulates the IPL function when loading by device address.
is the virtual address (cuu) of the device that contains the
nucleus to be loaded.
is the cylinder containing the IPL data. If this operand is
specified, CP loads the IPL data from the specified virtual instead of from virtual cylinder zero. Virtual cylinder zero is the default when cylno is not specified.
This operand is valid only for virtual direct storage devices.
sets the virtual storage space to binary zeros before the
operating system is loaded. This operand is invalid if you a svstemname in the IPL command line.
allows the contents of your virtual storage space to remain
unchanqed prior to program load. This operand is invalid if you soecify a systemname in the IPt command line. NO:LEAR is
the default if you IPL by device (vaddr).
halts the virtual machine during the IPL procedure just before
the initial PSW is loaded. It provides the virtual simulation
of the IPL procedure for a real machine in instruction step mode. The STOP operand is invalid if systemname is specified
in the IPL command. When the virtual machine stops, you can
issue CP commands. For example, if you are loading OS or OS/VS into your virtual machine, you can use CP commands to store data into low storage, to load an alternate nucleus, or to
alter the apparent size of virtual storage. To restart the
virtual machine, issue the BEGIN command.
simulates the IPL function when loading a named system that
was previously saved via the SAVESYS command. It is loaded
into virtual storage and qiven control. For information about
saved systems, see the 88 VM/370 CP Command Reference for General Users

IPL NQtg: You cannot load a shared system or one that uses disGontiguous saved segments into a virtual machine running in
the V=R area. An attempt to do so results in an error
message. PARM {p1 p2 ••• 1 passes up to 64 bytes of data (excluding the first blank
character after the keyword, PARM, but including all other
embedded blanks) to your virtual machine's general registers (4 bytes per register), starting with the high order byte of
general register o. since the registers are not cleared
before use, the PARM value should be some multiple of 4 bytes
to avoid having extraneous characters present in the low order
positions of the register. For example, you could key in PARr; eMSj) where represents a blank to ensure that the loy. ornAr positions of register 0 contain a hexadecimal 40. Whenever is specified, the remaining characters in the command
line are treated as parameters to be passed to your virtual
machine; therefore, PARK must be the last operand entered on
the command line.
1. IPL simulates the LOAD button and the device address switches on
the real computer console. The specified virtual address is
accessed and the required input/output operations are performed to
retrieve the IPL data.
2. the IPL procedure can be stopped just before loading
the virtual PSW except when initial program loading a named system.
Also, parameters can be passed to the virtual machine's general
registers. When the simulated load function is complete, CP initiates execution of the virtual machine by loading the 1PL PSi which was stored during the simulation process.
3. Care must be used when passing parameters to a named system (systemname). Named systems expect certain registers to be
initialized when they are given control. Indiscriminate use of the operand could overlay a previously initialized register
causing unpredictable results. 4. The IPL simulator program occupies one page (4096 bytes) of storage in your virtual machine. Therefore, if the system being loaded
utilizes data remaining in storage by the previous system, care
should be taken as to where that data is located. The starting
address of the overlaid virtual storage is: 256K and above
Less than 256K
For example:
= 1/2 the storage size
storage size=200K then the IPL Simulator is loaded at 100K. Section 5. Format of CP Commands 89