Asteroids emulator/source code port without the source

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tricky
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Asteroids emulator/source code port without the source

Post by tricky » Sun Sep 13, 2020 9:31 am

I've just finished a new port for the beeb of Asteroids.
Like my other "emulator" games it is actually a source code port, but with source code that comes from me disassembling the arcade ROM.
I don't want *. to get accused of distributing arcade ROMs, so the game loads the original ROMs and patches them to attach my beeb layer.
It expects two files that would be what you would get if you loaded your ROMs into MAME and then saved the memory ranges.
50rom58 is the ROMs that decode and load from &5000-&57FF inclusive.
68rom80 is the ROMs that decode and load from &6800-&7FFF inclusive.

https://youtu.be/1zH4hdREcTE best watch in 720p on a 50Hz monitor.
If you have a legal copy of the ROMS and are having difficulty making the appropriate files, please PM me.
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Asteroids-no-roms.zip
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KenLowe
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Re: Asteroids emulator/source code port without the source

Post by KenLowe » Sun Sep 13, 2020 9:49 am

That looks brilliant. It's been a long time since I've used MAME for arcade games so I'll need to go search for the ROMs. A job for later today. Does the attached code generate a SSD file I can then take to my Gotek?

Edit: After downloading the attached and reading your instructions again, I now get what I need to do. Does MAME allow you to dump memory chunks?

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tricky
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Re: Asteroids emulator/source code port without the source

Post by tricky » Sun Sep 13, 2020 12:13 pm

PM sent.
I have many sets of ROMs from old arcade machines that we scrapped where I used to work and unfortunately wasn't allowed to keep anything "with value". I use MAME to decrypt them or merge them when the originals were either split into nybbles or some other scheme.
run mame with -debug, then select your game and in the debug window's command entry line:save <filename>,<address>,<length> (can't remember if they are in hex or need 0x).
You can also Debug|New Memory Window to see where the ROMs are mapped to as the rest will probably be 0s.

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davidb
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Re: Asteroids emulator/source code port without the source

Post by davidb » Sun Sep 13, 2020 2:36 pm

Very good! I like the way you talk about how things are done while you show the results. :)

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tricky
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Re: Asteroids emulator/source code port without the source

Post by tricky » Sun Sep 13, 2020 3:30 pm

With most of the videos, I watch a bit and then record a sentence or two, so it works out that way, although sometimes it is planned :)

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TobyLobster
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Re: Asteroids emulator/source code port without the source

Post by TobyLobster » Sun Sep 13, 2020 7:00 pm

Very nice. I remember one time as a kid using up a lot of my birthday money in one session playing Asteroids for ages at the arcades on 10p a go BITD. The sounds certainly feel right to me. I imagine you have custom code to play sounds, or can you actually get away with using the regular OS versions of SOUND and ENVELOPE?

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tricky
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Re: Asteroids emulator/source code port without the source

Post by tricky » Sun Sep 13, 2020 7:29 pm

If I hadn't used all of the memory, SOUND could be used, but as I have also blocked interrupts, it's using my code which is actually very basic.

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oss003
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Re: Asteroids emulator/source code port without the source

Post by oss003 » Sun Sep 13, 2020 7:54 pm

Nice job Tricky ....
Great to see that you finished some games ...
Keep up the good work ... =D>

Greetings
Kees

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richardtoohey
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Re: Asteroids emulator/source code port without the source

Post by richardtoohey » Mon Sep 14, 2020 4:41 am

My memory not much cop these days, but pretty sure Asteroids was the first arcade game I laid my eyes on.

Didn't have much spending money in those days so I didn't waste much on it!

=D>

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kieranhj
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Re: Asteroids emulator/source code port without the source

Post by kieranhj » Mon Sep 14, 2020 6:45 pm

Excellent work Tricky, as ever! And a fantastic video, really interesting to hear about the details of making the game. :)

Now, about that 6502 copro version with line drawing in MODE 0. :-k :D
Bitshifters Collective | Retro Code & Demos for BBC Micro & Acorn computers | https://bitshifters.github.io/

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