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MPM OPERATING SYSTEMS/MPM I/MPM I SOURCE/15/patch04.tex

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+     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.
+