The X68000 games porting experiment

[Anima]

Hello guys,

as you might have alread read in the PacMania thread I am experimenting with porting X68000 games to the Atari ST.

The idea so far is to disassemble X68000 executable binaries in a way that the resulting source code quality is as good as the original so that you only need to rename the most important labels to understand how the game works. More important is that the reassembled version of the executable binary is identical to original as well.

For this task I have already written a disassembler which works fine so far (some mnemonic bugs are still present) in combination with the human68k and the m68k-atari-mint toolchains.

The first experiment was PacMania and the game logic already runs on the Atari STE (please see the PacMania thread for an example).

What are your thoughts, ideas and/or comments on that. Are you interested in some technical details? Please let me know.

Thanks
Sascha

[distantminds]

Hi!

i read with interest the Pacmania thread, and when you popped up in there with your ideas about x68000, i must say I think the idea is genius!

As i understand it, the X68000 is heavy on the custom chips, and it makes sense to me that it would in fact be easier to port these games than to make enhanced versions of existing ST titles. On an ST/E there's all manor of ways to draw sprites/backgrounds, but if you have a custom chip handling sprite/background draws, then I would imagine it would be much easier to intercept and replace the calls to the custom chips than unpicking exotic software based routines..

of course 'much easier' is relative

really cool idea!

[Zamuel_a]

What about dissamble a SEGA Megadrive game? It feels like it would be more or less the same as a X68000 game so maybe could be done with the same dissambler.

[qq1975b]

I tried to test the Pacmania X68000 adaptation you linked on the Pacmania's thread (http://atari-forum.com/viewtopic.php?f= ... &start=250) but I don't know if I have to do something special:
I copied all files in a 1,44MB disk (don't fit in a 720KB one) and tried to execute the PMSYS.TOS on my Atari Mega STE 4MB, but nothing happens. White screen, cursor on the left-up corner, and goes back to the desktop.

[Anima]

Hello guys.

As i understand it, the X68000 is heavy on the custom chips, and it makes sense to me that it would in fact be easier to port these games than to make enhanced versions of existing ST titles. On an ST/E there's all manor of ways to draw sprites/backgrounds, but if you have a custom chip handling sprite/background draws, then I would imagine it would be much easier to intercept and replace the calls to the custom chips than unpicking exotic software based routines..

Exactly. Another advantage is that the X68000 has no collision detection like the Atai 800 XL or C64 which would cost a lot of CPU power to emulate. So in this case the complete logic runs on the CPU.

What about dissamble a SEGA Megadrive game? It feels like it would be more or less the same as a X68000 game so maybe could be done with the same dissambler.

I am currently not aware of special hardware features of the SEGA Megadrive which would be problematic like the above mentioned collision detection but yes: that could be another target for porting games.

Also the NeoGeo is a potential candidate.

I copied all files in a 1,44MB disk (don't fit in a 720KB one) and tried to execute the PMSYS.TOS on my Atari Mega STE 4MB, but nothing happens. White screen, cursor on the left-up corner, and goes back to the desktop.

I have tested the executable under Hatari emulating an STE with 4 MB and TOS 1.62. However running the test under Steem crashes... well I'll take a look at it. It seems to be a problem calling Trap 15 functions in a Line F exception. Please stay tuned.

Cheers
Sascha

[Anima]

I tried to test the Pacmania X68000 adaptation you linked on the Pacmania's thread (http://atari-forum.com/viewtopic.php?f= ... &start=250) but I don't know if I have to do something special:
I copied all files in a 1,44MB disk (don't fit in a 720KB one) and tried to execute the PMSYS.TOS on my Atari Mega STE 4MB, but nothing happens. White screen, cursor on the left-up corner, and goes back to the desktop.

I've fixed a bug. Please try the pacmania archive again.

Cheers
Sascha

[Zamuel_a]

I don't know so much about the X68000 system, except that it was faster than Atari and used 65.536 colors so it seems like it would be better to make this conversion for a Falcon than on a regular STE.

[Anima]

I don't know so much about the X68000 system, except that it was faster than Atari and used 65.536 colors so it seems like it would be better to make this conversion for a Falcon than on a regular STE.

Agreed. Focusing the Atari Falcon 030 as the main target was the initial goal for me as well.

The "slowest" X68000 runs at 10 MHz. However, some games seem to have a very low CPU performance requirement so that an Atari ST(E) version can be considered as well.

Cheers
Sascha

[wongck]

why not port a game that is not available on the Atari but available on the X68000.
I am sure everyone will be "excited" about that.

[Anima]

why not port a game that is not available on the Atari but available on the X68000.
I am sure everyone will be "excited" about that.

Sure, but PacMania was already in an advanced state so that I decided to take it as a proof of concept.

What game do you think of being ported?

Some of what I can think of are:

Galaga 88
Mr. Do
Gradius
Parodius

However, the requirement is that the program is completely one relocatable executable for now.

Cheers
Sascha

[simonsunnyboy]

Galaga 88 would be great. I love that game both on MAME and the PC Engine.
It also should be feasible technically for ST standards.

[Mug UK]

Galaga 88 seconded.

[Stefan jL]

The x68000 version of Daimakaimura (Ghouls'n Ghosts) support General Midi... so it might been easy to extract the midi player and add to the ST version

[qq1975b]

I tried to test the Pacmania X68000 adaptation you linked on the Pacmania's thread (http://atari-forum.com/viewtopic.php?f= ... &start=250) but I don't know if I have to do something special:
I copied all files in a 1,44MB disk (don't fit in a 720KB one) and tried to execute the PMSYS.TOS on my Atari Mega STE 4MB, but nothing happens. White screen, cursor on the left-up corner, and goes back to the desktop.

I've fixed a bug. Please try the pacmania archive again.

Cheers
Sascha

I tried to test it again on my Atari Mega STe 4MB, 2.06 UK. It didn't work. Makes the same than the earlier version: white screen, cursor on the top left corner and back to the desktop.

It worked on Steem emulator 3.3.0 (it showed pacman on the low left corner in different views).

[Anima]

I tried to test it again on my Atari Mega STe 4MB, 2.06 UK. It didn't work. Makes the same than the earlier version: white screen, cursor on the top left corner and back to the desktop.

It worked on Steem emulator 3.3.0 (it showed pacman on the low left corner in different views).

Well, thanks for trying anyway. Unfortunately I have only my Falcon here to test the binary on a real machine (in fact, only a small fix within the Line F handling was necessary to get it working on the Falcon). Probably I need to dust off my STE to see what's wrong.

Cheers
Sascha

[wongck]

What game do you think of being ported?

Some of what I can think of are:
Galaga 88

Galaga 88 just jumped up and slap my face....
That's the one.

[MrMaddog]

I know it's still experimental right now, but it would be great to play a proper version of Street Fighter II...

And also the X68000 version of Castlevania is wicked. Played it on the PSX once, but it's so rare to find.

[Ato]

Galaga 88 seconded.

[Eero Tamminen]

I tried to test it again on my Atari Mega STe 4MB, 2.06 UK. It didn't work. Makes the same than the earlier version: white screen, cursor on the top left corner and back to the desktop.

It worked on Steem emulator 3.3.0 (it showed pacman on the low left corner in different views).

Well, thanks for trying anyway. Unfortunately I have only my Falcon here to test the binary on a real machine (in fact, only a small fix within the Line F handling was necessary to get it working on the Falcon). Probably I need to dust off my STE to see what's wrong.
Sascha

What about Hatari? I've understood that its latest version (1.6.2) has now more accurate STE emulation than Steem.

(Steem's GUI debugger is much nicer to use, but Hatari's command line debugger is also fairly powerful, especially with the latest updates in Hatari repository.)

[Anima]

What about Hatari? I've understood that its latest version (1.6.2) has now more accurate STE emulation than Steem.

Thanks for the suggestion but Hatari is already my favourite emluator. I just switched to the Atari Falcon as the porting target so Hatari is perfect so far.

Cheers
Sascha

[Anima]

Helly guys,

just a status update on the Galaga 88 port: the source is disassembled and can be fully functional reassembled as well. Label renaming in progress...

In the meantime I was wrinting some test routines for the PacMania port so that the Galaga 88 work slowed a bit down.

Cheers
Sascha

[Anima]

Hello guys,

emulating the PacMain on a "stock" Atari Falcon 030 currently looks like this now:

X68000 PacMania on the Atari Falcon 030 Video on YouTube

Buggy, slow and incomplete but rather impressive due to the 384x240 pixels size compared to the 256x256 on the X68000.

The video shows only the attract mode till it freezes but you can already play the game as well (press trigger to start). However, playing is no fun without seeing the pills!

Cheers
Sascha

[EvilFranky]

Absolutely gobsmacked, incredible work.

So does the X68000 use a 16-bit screen in PacMania? Can't the VIDEL be programmed to match the exact X68000 resolution, meaning less has to be drawn to the screen?

Do you think the Falcons DSP will be able to emulate a Yamaha YM2151??

Keep up the great work!

[Marakatti]

Yes, amazing stuff! I wonder how it would run on Centurbo II or other 030 accelerator

[CiH]

Just - Wow! -

Moar please!!