Posted: 5/18/2009 2:00 PM
Post subject: The "Double Dribble" test - Luck manipulation on a real NES?
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Dwedit
He/Him
Joined: 3/24/2006
Posts: 692
Location: Chicago
Does anyone out there have a NES, and a Double Dribble cartridge? Double Dribble and most other Konami Games use a random number generator which is called at the end of every frame, and keeps running until the next frame starts. Double Dribble plays a randomly selected Dunk animation after waiting a few seconds at the title screen. Double Dribble also plays a DMC sample during the title screen. The DMC channel can mess with the CPU a bit, by stealing CPU cycles at various times, which can affect the RNG. The DMC channel is NOT reset by starting a sample, so its behavior could possibly vary depending on the power-up condition of the NES. Here's the test: Does the exact same sequence of dunk animations play in the exact same order every time you boot the NES from a cold boot? If the same sequence of animations plays back every time, luck manipulation is possible if played back on hardware. If the sequence varies between bootups, then it isn't. There's also a third possibility: Three possible random sequences due to an undefined PPU/CPU sync on bootup.
Posted: 5/19/2009 6:02 PM
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DaTeL237
Active player (356)
Joined: 1/16/2008
Posts: 358
Location: The Netherlands
The more important question would be whether it is emulated properly i think? because if it synchs with an input-file, basic luck manipulation is always possible simply by trial-and-error just my 2c
TASes: [URL=http://tasvideos.org/Movies-298up-Obs.html]Mr. Nutz (SNES), Young Merlin 100% (SNES), Animaniacs 100% (SNES)[/URL]
Posted: 5/20/2009 1:21 AM
Post subject: Re: The "Double Dribble" test - Luck manipulation on a real NES?
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Xkeeper
Banned User
Joined: 12/23/2004
Posts: 1850
I'll get back to you in a month or so. At the moment the only way I can play Dubble Dibble on an NES is via PowerPak and we all know how useful that is in checking cold-boot statuses.
Perma-banned
Posted: 5/20/2009 2:17 AM
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Tristal
Joined: 7/10/2007
Posts: 280
I'd love to test it for you, but I don't have a Double Dribble cart, nor do I believe I have any other Konami carts.
Posted: 5/20/2009 6:15 AM
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Dwedit
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Joined: 3/24/2006
Posts: 692
Location: Chicago
The Demo of Blades of Steel should also work too. I just need to know if it plays the same on a NES every time, or varies. On FCEU, it varies! On Nintendulator, it plays the same every time. On Nestopia, it plays the same every time, but is different from Nintendulator. Basically, anything made by Konami that plays DMC samples before showing randomness with no joystick input should work, but the only two games that actually do that are Double Dribble and Blades of Steel. Contra sort-of shows differences, with Contra, you can see that FCEUX has a slightly different Demo then Nestopia, in FCEUX, two enemies fail to get killed.