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RE: [midatlanticretro] Question about Assembly/CUTTER/VDM-1

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  • Bill Sudbrink
    Hi Bill, The D3 8C is an OUT instruction. This is an I/O address, not a memory address. I don t have anything at hand to remind me the I/O addresses used
    Message 1 of 3 , Mar 30 12:02 PM
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      Hi Bill,

      The 'D3 8C' is an OUT instruction. This is an I/O address, not a memory address.
      I don't have anything at hand to remind me the I/O addresses used by a VDM card
      configured for CUTTER.

      I would keep the VDM init code, in case the rest of the program expects the card
      to be in some other state besides the one CUTTER sets it to. The program seems
      to want to load and execute at address $0000. You will notice the JMPs and CALLs.
      The one "odd ball" thing about this program is that it seems to expect the VDM
      memory buffer to be at $8800. This is not where CUTTER wants it, so this is probably
      not where yours is. I would think yours is at $CC00, that is where CUTTER expects
      it. The loop starting at $000A (label ST) fills the buffer with 20H (space character).

      I can probably tell you about the I/O addresses when I get home.

      Bill S.

      > -----Original Message-----
      > From: midatlanticretro@yahoogroups.com [mailto:midatlanticretro@yahoogroups.com]On Behalf Of Bill Degnan
      > Sent: Monday, March 30, 2009 2:36 PM
      > To: midatlanticretro@yahoogroups.com
      > Subject: [midatlanticretro] Question about Assembly/CUTTER/VDM-1
      >
      >
      > I wish to understand how to move the memory used by the following program
      > info below the 8000 page boundary, and whether I need to initialize VDM-1
      > or just skip, in the following exercise from Dr. Dobbs:
      >
      > http://vintagecomputer.net/CISC367/dr%20dobbs%20sept%201976%20VDM-1%20Demo%2
      > 0Program.pdf
      >
      > Could someone explain to me whether I need the first 2-9 lines of this
      > code, if using CUTTER? I am also thinking of changing lines like
      >
      > 0005 D3 8C
      >
      > to
      >
      > 0005 D3 4C
      >
      > ...to move to a place where I have space in memory (rather than adding more
      > memory to the computer). I am correct to just change the 8's to 4's
      > (assuming there's free space)? Note the places in the code with the
      > asterisks.
      >
      > My IMSAI uses 0000 through 7FFF for RAM and CUTTER is written to C000-Cxxx
      > using the memory on the general purpose card.
      >
      > Bill
      >
      >
      >
      >
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