     MP/M 1.0  *** Patch ***  10/17/79

     Page Zero Initialization with Bank Switched Memory
     __________________________________________________

     The following patch is required only if you have written
an XIOS which supports bank switched memory.  The nature of
the problem is that the jump instruction at location 0000,
at your interrupt entry points, and at the selected debugger
breakpoint restart location must be initialized in each of
your memory banks.

     The patch is performed in the SYSINIT procedure of your
XIOS as follows:

     o Determine the BDOS base address by running GENSYS and
       then the MPMLDR.  The MPMLDR will display the memory map
       showing the BDOS base address.

     o Once the BDOS base address has been determined, place the
       following instructions into your SYSINIT procedure:

       SYSINIT:
               ...
               ...

       ; Loop through all banks
       LOOP:
               ; Switch in the next bank

               MVI     A,0C3H
               STA     0000H
               LXI     H,BDOS+0091H
               SHLD    0001H

               STA     BRKPTRST*8
               LXI     H,BDOS+0101H
               SHLD    BRKPTRST*8+1

               ; Store appropriate jumps to your XIOS
               ;   for the interrupt entry points

               ...

               JMP     LOOP

     o Note that this patch requires that you leave the BDOS
       at the established base.
