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Space Invaders

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  • herc_fun
    Hi group, I m a newbie here. I have an awesome Space Invaders game that I wrote about 20 years ago for the ELF II. Full graphics and gameroom action and all.
    Message 1 of 5 , Mar 2, 2002
      Hi group, I'm a newbie here. I have an awesome Space Invaders game
      that I wrote about 20 years ago for the ELF II. Full graphics and
      gameroom action and all. It even makes Q click when you hit suff! (If
      you were one of those folks who pu a speaker on Q). I still have
      machine readable source code for it (actually the code exists on a
      mainframe where my 1802 cross-assembler lives). I want to run this
      code again but my actual ELF hardware is somewhat less than operative.
      What's the status of emulators for ELF II? (I know there is the
      original ELF emulator complete with toggles but is needs the 4k
      expansion card etc...) Anyone got an interest in this?

      Old but sill 8bit at heart.
      Charlie
    • Dave Ruske
      Sounds like a nice piece of work, Charlie! I presume you were using the 1861 for graphics? TinyELF (the emulator for the Palm OS) could probably run the code,
      Message 2 of 5 , Mar 2, 2002
        Sounds like a nice piece of work, Charlie! I presume you were using the 1861
        for graphics?

        TinyELF (the emulator for the Palm OS) could probably run the code, depending
        on what you used for game control. One shortcut I took in TinyELF was the use
        of regular button objects for the hex keypad --- and the side effect is that
        while one of those buttons is pressed, 1802 code execution is effectively
        paused while the Palm OS sits and spins. I did something special for the
        Input key (programmed it using a gadget) so that one doesn't exhibit that
        behavior. I keep meaning to get back to TinyELF's code to add some features
        (such as a sorely-needed program import), but as priorities go that project
        usually gets trumped.

        The other, more obvious, problem with TinyELF is that it *crawls*. You'd
        think that emulating a 1.79 MHz 8-bit machine on a 20+ MHz Dragonball would
        be quicker, but in practice the code needs to do a lot of cycle counting to
        properly emulate the Pixie graphics. When Palm comes out with their 200 MHz
        ARM handhelds, I think TinyELF may be able to approach the speed of a real
        ELF.

        Bill Richman's emulator (the one I think you refer to) may run the code, but
        it depends... last time I played with it, the STXD instruction didn't work,
        and I don't believe that emulator has been updated. As I recall, the
        instruction did the store-via-X but didn't decrement afterwards. If you're
        using X as a stack pointer while running a virtual 1861, there's no easy fix
        for this. Adding a decrement alone wouldn't work, because an interrupt could
        hit between the STX and the DEC and nail the stack.

        By the way, let me know if you'd like to make your Space Invaders game
        available to others. I've just recently created a software area on
        cosmacelf.com, and I'd welcome any such contributions.

        Dave

        On Saturday 02 March 2002 08:30 pm, you wrote:
        > Hi group, I'm a newbie here. I have an awesome Space Invaders game
        > that I wrote about 20 years ago for the ELF II. Full graphics and
        > gameroom action and all. It even makes Q click when you hit suff! (If
        > you were one of those folks who pu a speaker on Q). I still have
        > machine readable source code for it (actually the code exists on a
        > mainframe where my 1802 cross-assembler lives). I want to run this
        > code again but my actual ELF hardware is somewhat less than operative.
        > What's the status of emulators for ELF II? (I know there is the
        > original ELF emulator complete with toggles but is needs the 4k
        > expansion card etc...) Anyone got an interest in this?
      • herc_fun
        ... the 1861 ... depending ...... ... code, but ...... ... game ... The game ran on the original Netronics ELF II with a 4k memory expansion card. I made my
        Message 3 of 5 , Mar 5, 2002
          --- In cosmacelf@y..., Dave Ruske <dave@r...> wrote:
          > Sounds like a nice piece of work, Charlie! I presume you were using
          the 1861
          > for graphics?
          >
          > TinyELF (the emulator for the Palm OS) could probably run the code,
          depending ......
          >
          > Bill Richman's emulator (the one I think you refer to) may run the
          code, but ......
          >
          > By the way, let me know if you'd like to make your Space Invaders
          game
          > available to others....
          > Dave


          The game ran on the original Netronics ELF II with a 4k memory
          expansion card. I made my own joystick which "piggy backed" on the
          hex keypad and input button lines I believe so the game could be
          played without the custom joystick. It used every available cycle;
          in fact it wouldn't even display the score unless there were enough
          cycles left over to convert the score to decimal and display it.
          Speaking of score, I used the 8bit output port on the memory
          expansion card to hook up another 2 seven-segment displays to give a
          total of 4 hex-digit display.

          It would be interesting to know of this code running again; whether
          on classic hardware or an emulator. To that end, I am forwarding
          Dave a zipped assembly listing of the code and a binary memory image
          for posting on his cosmacelf.com site. I'll monitor this discussion
          group and attempt to answer questions if anyone undertakes reviving
          this program. By the way, the first question regarding the program
          may be "why is there a long branch to 0xF000 at the start of the
          code?"; That is where the ROM monitor program lived on ELF II which
          let you read/write casette tape, display/alter memory and start
          program execution at location 0x0003.

          If there is interest in this one, I'm willing to post my LIFE program
          and ELFIGOL (ELF Interpretive Game Oriented Language).
        • druske
          I ve posted the text and binary versions of Charlie Brint s Space Invaders game to the software archive on cosmacelf.com. It s likely to be some time before I
          Message 4 of 5 , Mar 5, 2002
            I've posted the text and binary versions of Charlie Brint's Space
            Invaders game to the software archive on cosmacelf.com. It's
            likely to be some time before I get a chance to give it a whirl
            myself, but if someone else gets it running (or has troubles) please
            let us know!

            Dave
          • jdrose_8_bit
            That is cool. I knew about Mr. Robson s Invaders for the Studio II. Did not know there was one for the Elf II. I found this one in the files section:
            Message 5 of 5 , Mar 8, 2013
              That is cool. I knew about Mr. Robson's Invaders for the Studio II. Did not know there was one for the Elf II.

              I found this one in the files section:
              http://groups.yahoo.com/group/cosmacelf/files/Elf%20II/

              Is this one yours?


              >
              > Hi group, I'm a newbie here. I have an awesome Space Invaders game
              > that I wrote about 20 years ago for the ELF II. Full graphics and
              > gameroom action and all. It even makes Q click when you hit suff! (If
              > you were one of those folks who pu a speaker on Q). I still have
              > machine readable source code for it (actually the code exists on a
              > mainframe where my 1802 cross-assembler lives). I want to run this
              > code again but my actual ELF hardware is somewhat less than operative.
              > What's the status of emulators for ELF II? (I know there is the
              > original ELF emulator complete with toggles but is needs the 4k
              > expansion card etc...) Anyone got an interest in this?
              >
              > Old but sill 8bit at heart.
              > Charlie
              >
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