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Sonic & Knuckles: lock-on imperfect emulation #103640 01/14/16 12:55 PM
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xinyingho Offline OP
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Hi there,

I got 3 cartridges of Sonic & Knuckles (JP, US and EU versions). So I tested those on my European Mega Drive by stacking them and see what happens.

I found out that you can stack 2 or 3 S&K cartridges, but it won't change anything to the way the lock-on technology works: it simply ignores the additional S&K cartridges. You can put Sonic 3 on top of the stack, no matter the number of S&K cartridge there is, you'll still get Sonic 3 & Knuckles.

Then I tested the same operations on MAME. I couldn't get very far: as soon as you virtually stack 2 S&K cartridges, MAME simply crash outputting the exception stack.

I thought I should report this bug.

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103641 01/14/16 01:28 PM
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LoganB Offline
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Exception stack:
Code:
  000000000836F140: 00000000014F5B31 (winmain_dump_stack()+0x0041)
  000000000836F200: 00000000029756E9 (osd_break_into_debugger(char const*)+0x0029)
  000000000836F250: 00000000024C8FB2 (emu_fatalerror::emu_fatalerror(char const*, ...)+0x0052)
  000000000836F3B0: 000000000253C71D (machine_config::machine_config(game_driver const&, emu_options&)+0x039d)
  000000000836F520: 00000000024C94BA (emu_options::add_slot_options(bool)+0x00aa)
  000000000836F6A0: 00000000024C9D3A (emu_options::update_slot_options()+0x010a)
  000000000836F710: 00000000024CA21B (emu_options::parse_slot_devices(int, char**, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&, char const*, char const*)+0x00bb)
  000000000836F770: 00000000024CA32A (emu_options::parse_command_line(int, char**, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&)+0x004a)
  000000000836F950: 000000000248733F (cli_frontend::execute(int, char**)+0x05df)
  000000000836FDF0: 00000000014F500B (utf8_main(int, char**)+0x016b)
  000000000836FE50: 000000000297311E (wmain+0x007e)
  000000000836FF20: 000000000040140C (__tmainCRTStartup+0x025c)
  000000000836FF50: 000000000040153B (mainCRTStartup+0x001b)
  000000000836FF80: 00007FFB52588102 (BaseThreadInitThunk+0x0022)
  000000000836FFD0: 00007FFB54E4C2E4 (RtlUserThreadStart+0x0034)
Unknown slot option 'rom_sk' in slot 'mdslot:rom_sk:subslot'

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103642 01/14/16 02:39 PM
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Haze Offline
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it's a fatalerror, so it's already telling us what the problem is without the backtrace, basically the sk cart slot device isn't designed to take an sk cart ;-)

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: Haze] #103651 01/14/16 07:25 PM
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Just Desserts Offline
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Originally Posted By Haze
it's a fatalerror, so it's already telling us what the problem is without the backtrace, basically the sk cart slot device isn't designed to take an sk cart ;-)


That's just bad implementation, then. S&K could be used with just about any Mega Drive game: It would display a "this game is not designed for use with Sonic & Knuckles" screen, but if you punched in a button combo, it would take you to an infinite series of bonus rounds, the ordering being seeded by some sort of data from the locked-on cartridge.

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103652 01/14/16 07:30 PM
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S&K will accept any Mega Drive game. It just won't accept another instance of itself, which in real life has no effect and may cause magic smoke to come out of your power brick if you do it too often.

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103653 01/14/16 07:51 PM
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xinyingho Offline OP
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Actually, S&K won't always show the special "No Way" screen for every games. I've tested with Sonic 3D Flickies Island on the top, and I just got the regular S&K intro. I think that S&K activates the "No Way" screen for any games released before it bu not necessarily for every game released after.

Re: Sonic & Knuckles: lock-on imperfect emulation [Re: Just Desserts] #103654 01/14/16 07:52 PM
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I'm assuming that must be an EU or JP thing, in the US we just got a screen saying "NO WAY! NO WAY! NO WAY!" which, while fitting with the XTREME AWESOME era of the 90s, was more alarming than anything and "hit some buttons to get a random bonus stage" never came up until some friend or game magazine told you about it.

I think there were a few games that didn't work with S&K, I don't remember if they didn't boot or if S&K booted with random issues or something. I feel like it was some of the later games with more ROM space....

EDIT: Ahh ok... "Any connection with games that, when added to Sonic & Knuckles, become greater than 4MB (such as Super Street Fighter II) will prompt Sonic & Knuckles to start up as usual, without Blue Sphere activating. This is because when locked-on to a ROM larger than 2MB, Sonic & Knuckles maps the last 2MB of the locked-on ROM rather than the first 2MB, so when Sonic & Knuckles tries to read the locked-on header, it actually reads from the second half of the ROM, finds no header, and loads Sonic & Knuckles normally. An exception to this is Sonic Classics, which happens (or was designed?) to put Sonic the Hedgehog at the 2MB mark. This is a quirk in the Sonic & Knuckles cartridge's mapper, which is not reproduced in emulators."

Last edited by Sharkpuncher; 01/14/16 07:55 PM.
Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103655 01/14/16 07:56 PM
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xinyingho Offline OP
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@Sharkpuncher: I think that the "this game is not designed for use with Sonic & Knuckles" screen actually refers to the "No Way" screen.

Edit: really interesting finding. What is the source of your edit text?

Edit2 : found the source (http://info.sonicretro.org/Blue_Sphere). It seems like somebody actually succeeded to go through all the Blue Sphere levels of S&K+S1!
"[...] with a total of 134,217,728 levels in all. However, after level 128,016,000 some of the previous levels begin to reappear. After completing all 134,217,728 stages it restarts from the beginning" !!

Last edited by xinyingho; 01/14/16 08:06 PM.
Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103656 01/14/16 10:06 PM
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That's some dedication, wow. I can't imagine going through that many levels, that sphere game was pretty annoying to me.

And yeah, I just googled it quickly, I know that it's just anecdotal information from a random fan wiki but at least it seems like they've explored/hacked a lot of the hardware in various ways and that makes more sense than it being some arbitrary "works/doesn't work" based on ???? per game.

(That being said maybe they also found some way to go through all the levels without having to play each one, for that matter.)

Last edited by Sharkpuncher; 01/14/16 10:06 PM.
Re: Sonic & Knuckles: lock-on imperfect emulation [Re: xinyingho] #103657 01/14/16 10:20 PM
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xinyingho Offline OP
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Sonicretro is actually a very well known site, filled with people dedicated to hack into every Sonic games they find to make derivative games or salvage any interesting data. We can definitely trust what their wiki says.

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