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PostPosted: Wed Feb 05, 2014 12:50 pm 
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A long time ago, my friend and I were messing around with Parasol Stars and somehow started a two-player game with only one controller plugged in and no Turbo Tap.* I can't remember if both players were controlled simultaneously. It could have been a debug code to let the developer test the two player game, but can anyone rule out or affirm the possibility it was a hardware glitch? I might disassemble the game to figure out what happened.

* For those who don't know TG-16 hardware, it only has one controller port without the Turbo Tap, which is a pretty snicker-happy name in itself.


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PostPosted: Wed Feb 05, 2014 12:58 pm 
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Micro Machines games have a tradition of letting two players share a controller: player 1 steers with the Control Pad and player 2 steers with the face buttons. The Jeopardy! games for NES have players 1 and 3 sharing controller 1 in the same way. The 2-player minigames in WarioWare Inc.: Mega Microgame$ share a GBA, with one player using the L button and the other player using R. I imagine that any one- or two-button game could be adapted in this way.

Next you'll probably tell me "two girls, one cup" wasn't about how Peach and Daisy won the championship trophy in Mario Kart Double Dash or Mario Power Tennis doubles.


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PostPosted: Sat Feb 08, 2014 8:56 am 
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strat wrote:
A long time ago, my friend and I were messing around with Parasol Stars and somehow started a two-player game with only one controller plugged in and no Turbo Tap.* I can't remember if both players were controlled simultaneously. It could have been a debug code to let the developer test the two player game, but can anyone rule out or affirm the possibility it was a hardware glitch? I might disassemble the game to figure out what happened.

* For those who don't know TG-16 hardware, it only has one controller port without the Turbo Tap, which is a pretty snicker-happy name in itself.


That's odd. Looking briefly at the TG-16 controller hardware it seems operationally identical to a Sega Mega Drive (74HC157 multiplexing).The Turbo Tap sounds very simple:

Quote:
The counter can be reset by holding SEL high and doing a zero-to-one
transition on CLR. At this point, you can then strobe SEL five times
to read each controller. Once all five controllers have been read,
the Turbo Tap will return $00 in D3-D0 until the counter is reset again.
Unconnected controllers always return $0F in D3-D0.


Now, let's rule out something simple - are you sure Parasol Stars doesn't allow Player 1 to start a two player game regardless of controller availability?


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PostPosted: Sat Feb 08, 2014 9:45 pm 
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Parasol Stars is an arcade-style game where the second player can press run at any time to join in. There's no option for the first player to initiate a two-player game. I just looked at the game with Mednafen and found the check for the sound test cheat (F09A in the rom) but that's the only special button combination checked for. It seems what happened had to be a glitch.

And I'm starting to think it was a software glitch, because a) the original incident took place after a gameover and b) the game does five controller reads (E19C) and on pressing start, it compares the controller state for players one and two with the third read which is a dummy (E205). If all three states are equal, a one player game is assumed. This indicates PCE games have to do a software check for the presence of a Turbo Tap and second controller. It's possible that somehow this check got skipped after starting over from the last game, giving the lone controller both players.

It'll take more debugging to figure this out...


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PostPosted: Sun Feb 09, 2014 8:59 am 
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Quote:
Parasol Stars is an arcade-style game where the second player can press run at any time to join in. There's no option for the first player to initiate a two-player game. I just looked at the game with Mednafen and found the check for the sound test cheat (F09A in the rom) but that's the only special button combination checked for. It seems what happened had to be a glitch.


A rare bounce condition with start button? Or a momentary connection fritz of the plug and the port, resulting in the same?

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PostPosted: Mon Feb 10, 2014 12:39 pm 
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That's probably it. The controller state somehow changed between the second and third read, fooling the game into starting with two players. That wouldn't be an easy glitch to reproduce.


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