IBM Professional Series User Manual page 376

F5 Key - Edit (Real/Virtual)
Press the F5 key to display VIRTUAL STORAGE. The
virtual storage display overlays the real 370 storage display.
Press F5 again to display the real 370 storage again. By
pressing F5 you can switch between displays of real and
virtual storage in the storage display area of the screen. If
the data for a virtual address is not currently in storage, the
storage contents will be displayed as "X"s and the fields will
be locked.
F4 Key - Edit PAT/Edit Main
Press F4 to edit the PAT (Page Address Table). This is the
hardware table that maps virtual addresses to real addresses.
The PAT edit screen data overlays the 370 storage edit data.
Pressing the F4 key again causes the storage edit data to be
displayed again.
The PAT edit format has a column of virtual addresses on
the far left of the screen, followed by columns of the
corresponding real addresses, the valid bits, the reference
bits, and the change bits respectively. For further
information on the PAT, see the "IBM Personal Computer
XT /370 Technical Manual," and the section on Dynamic
Address Translation in the "370 Principles of Operations."
You should only alter the PAT data if you absolutely know
what you're doing. Virtual storage management is a function
of the 370 operating system. Altering this data could cause
unpredictable results.
Address Compare Stop Function
The address compare feature automatically stops the 370
processor when it detects an instruction execution at an
address you've entered. To use this function, enter the
address in the Address Compare Field located in the status
area on the screen. You need not supply leading zeros of the
address, but may type any non-valid hexadecimal character
after the last entered digit. If you enter an invalid address,
such as too large, the 370 Processor Control utility makes
Appendix B. The 370 Processor Control Session B-7