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Help me get into this guy's mind: 8086 INC/DEC pairs

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    #16
    Originally posted by per View Post
    And 6502 does indeed set Zero and Sign flags on register load.
    Yes, that might explain it... It seems to emit the inc/dec sequence after every mov reg, mem operation.
    Apparently that code was 'good enough'... even though the translation is probably slower than on a real 6502.
    Otherwise I guess they would have made the translator just a bit more clever, and only emit the sequence when a following instruction actually looks at the flags, rather than just overwrite them.
    http://scalibq.wordpress.com/just-ke...o-programming/

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      #17
      So the INC/DEC on AL when CL is loaded at 5E18 is an error? And the author didn't notice it?
      Reach me: vcfblackhole _at_ protonmail dot com.

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        #18
        The PC version was transcompiled; what you're seeing is an error in the transcompilation.
        Offering a bounty for:
        - A working Sanyo MBC-775 or Logabax 1600
        - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

        Comment


          #19
          Originally posted by Trixter View Post
          The PC version was transcompiled; what you're seeing is an error in the transcompilation.
          Exactly my point. If it's a transcompilation, the error must have occurred again and again in the process. And apparently with no bad effect.
          Reach me: vcfblackhole _at_ protonmail dot com.

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            #20
            Originally posted by Chuck(G) View Post
            So the INC/DEC on AL when CL is loaded at 5E18 is an error? And the author didn't notice it?
            Could be... The 6502 only has one accumulator, so perhaps they didn't think of that when writing the transcompiler. What is interesting though is that it would actually use cl in that case... So they did think of that
            Weird.
            http://scalibq.wordpress.com/just-ke...o-programming/

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              #21
              My guess is that the first version of the transcompiler/macro set didn't do the INC/DEC thing and the game didn't work. The addition of the INC/DEC was done as a shotgun-style "Hail Mary" maneuver and probably with a manager breathing delivery schedules down the neck of the poor programmer.
              Reach me: vcfblackhole _at_ protonmail dot com.

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                #22
                Originally posted by Chuck(G) View Post
                So the INC/DEC on AL when CL is loaded at 5E18 is an error? And the author didn't notice it?
                CL is being loaded with AL, so it's the same value anyways. It's not clean, but it still works as intended.
                Current systems owned by me:
                Vintage:IBM PC/XT submodel 087 ( 1983 ), [Kon]tiki-100 rev. C (1983), Compaq Portable I ( 1984 ), IBM PC/XT submodel 078 ( 1985 ), IBM PC/XT286 ( ~1986 ), 3x Nintendo Entertainement Systems ( 1987 ).
                Obsolete:Commodore A500 ( ~1990 ), IBM PS/2 model 70/386 type 8570-161 ( 1991 ), Atari Lynx II ( ~1992 ), Generic Intel 486SX PC ( ~1993 ), AT/T Globalyst Pentium w/FDIV bug MB ( 1994 ), Compaq 486DX4 laptop ( ~1995 ).

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                  #23
                  Originally posted by Trixter View Post
                  Steve Hays, who wrote the Apple II version, got in contact with me and told me the person who did the trans-compilation system was Dana Howe. Hopefully I can get in contact with them and can report back.
                  I thought the name sounded familiar, and indeed - a Dana How (sans "e") worked on the PC port of EA's Hard Hat Mack, "through TMQ Software, Inc". Maybe the different spelling and the TMQ lead would be helpful there.

                  (Speaking of which, I wonder if a blog entry about my own silly hack would still be interesting)
                  int10h.org :: :: :: blog

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                    #24
                    Originally posted by el_VR View Post
                    I thought the name sounded familiar, and indeed - a Dana How (sans "e") worked on the PC port of EA's Hard Hat Mack, "through TMQ Software, Inc". Maybe the different spelling and the TMQ lead would be helpful there.
                    Good catch -- Hard Hat Mack has the same kind of transcoding shenanigans going on:

                    Code:
                    seg000:1249                 mov     al, 79h
                    seg000:124B                 inc     al
                    seg000:124D                 dec     al
                    seg000:124F                 mov     byte_111EF, al
                    (Speaking of which, I wonder if a blog entry about my own silly hack would still be interesting)
                    It would, considering how you managed to fix the graphics without knowing any assembler!
                    Offering a bounty for:
                    - A working Sanyo MBC-775 or Logabax 1600
                    - Music Construction Set, IBM Music Feature edition (has red sticker on front stating IBM Music Feature)

                    Comment


                      #25
                      Originally posted by Trixter View Post
                      It would, considering how you managed to fix the graphics without knowing any assembler!
                      Yes, I take it they were not compiled sprites then. Because those would be very hard to modify afterwards.
                      The modified version looks really great too!
                      Reminds me of Burger Time, perhaps one of the best composite CGA arcade ports made.
                      http://scalibq.wordpress.com/just-ke...o-programming/

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