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ItemDex/RB:085: Difference between revisions
→Hall of Fame corruptions
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==Hall of Fame corruptions==
As the process is complex, viewing certain glitch Pokémon sprites without further knowledge can be viewed as an elaborate pseudo-random number generator, if the initial SRAM is interpreted as a 'seed' (pseudo-random as given the sprite pointer of a glitch Pokémon is not from RAM or SRAM itself, the input SRAM would in theory always produce the same output SRAM).
Coincidentally, the player may come across a desirable outcome after running B1F following these corruptions.
However, it is possible to calculate an exact series of corruptions required for a given result using TheZZAZZGlitch's SRAM corruption emulator.
First, a known series of bytes can be used for seeding the "SRAM RNG"; such as a series of FF bytes from resetting the game, or the [[game freeze]] from [[GlitchDex/RB:193|ゥ (0xC1)]] (itself, influenced by a front sprite pointer of VRAM:8E8F - which may effectively be the data on the screen just before battle; the font, map sub-tiles, process of the battle transitions to turn sub-tiles solid black can alter this) - in this case, it is sometimes able to fill a portion of the SRAM (including the region accessed by B1F) with a continuous 00 39 or 39 00 pattern.
This is due to a rst 38 (restart vector 0x38, opcode 0xFF which jumps to 0038 containing another rst 38 (0xFF) instruction; corrupting the memory downward from the stack (late DFXX area in WRAM), including potentially the SRAM) to match the pointer of the following address 00 39. The player can test if the desired area became 00 39 from checking the Hall of Fame following a game freeze by ゥ (0xC1) and viewing a series of Level 57 [[GlitchDex/RB:000|'M (00)]] in the Hall of Fame, because the decimal Level 57 corresponds with the hexadecimal 0x39, and these 'M have the index number 0 (0x00).
Next, TheZZAZZGlitch's SRAM corruption emulator can be used to calculate the required sequence of Hall of Fame corruptions from glitch Pokémon sprites from the party menu, leading to the desired sequence of bytes. A downside of the SRAM corruption emulator however, is that certain (or longer) sequences of bytes may result in an extremely very long computation time.
[[GlitchDex/RB:198|LM4 (0xC6)]] (relative upper area of the SRAM) and [[GlitchDex/RB:220|Glitch Pokémon (0xDC)]] (relative lower area of the SRAM) are examples of glitch Pokémon which corrupt the Hall of Fame, and were verified by TheZZAZZGlitch for use with the SRAM corruption emulator.
Note this method is not only useful for B1F. For example, the contents of [[TrainerDex/RB:052|Trainer (0x34)]]'s roster 1 (0xFC from 0xD059 and 0x01 from 0xD05D, hence the required Special stat is 252, and the required Attack stat modifier is -6. Specifically however, it is just the representation of $CD2D and $CD2E effectively) depends on the contents of pointer 0xA5A5 in SRAM. This is within the region that can be changed through glitch Pokémon sprite corruptions such as LM4. If the player is able to corrupt the sprite pointer region of a glitch Pokémon for those sourced in SRAM like [[GlitchDex/RB:244|ゥ₽ (F4)]] and its front sprite pointer of SRAM:A922, grinding (or calculating the series of corruptions) for an interesting front sprite is an option as well (see also: [[arbitrary sprites]]).
While Hall of Fame corruptions through glitch Pokémon sprites may be appealing in their own ways, they are not necessary if the player wants more control and efficiency, as the player could simply modify the SRAM with arbitrary code execution precisely in advance, nonetheless it can be desirable by some to grind for a desirable result in advance.
Theoretically, an even more relatively chaotic corruption of the SRAM could be achieved with arbitrary code execution as well; such as through the player's own pseudo-random number generator that they programmed themselves, or perhaps through grabbing environmental noise from the Game Boy Color's infrared port.
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