core: list of unimplemented or incorrect emulation

[deltabeard]

List of behaviours that aren't currently emulated properly in Peanut-GB.

LCD

• The LCD is emulated line by line, where a line is rendered when the LCD enters Mode 3 (Reading OAM and VRAM to generate the picture).
  • Mid-scanline effects will not be rendered (changing BGP during Mode 3).
• The duration of Mode 3 is constant, and does not change with the number of sprites rendered. This means that the duration of Mode 0 is also constant. The duration of Mode 0 is made to be the maximum possible regardless of sprites rendered on the line.
• Sprite fetch abortion is not emulated.

CPU

• I/O registers are only updated after an instruction is executed, not during. The https://github.com/deltabeard/Peanut-GB/tree/mem-accuracy branch implements this however.
• Joypad interrupts are implemented, but requires further testing. Joypad interrupt does not fire #34
• SGB is not implemented. There is CGB support in the https://github.com/deltabeard/Peanut-GB/tree/cgb branch which will be merged into the master branch after further testing. CGB Support #50
• Obscure timer behaviour specified in https://gbdev.io/pandocs/Timer_Obscure_Behaviour.html may not be implemented.
• The HALT bug specified in https://gbdev.io/pandocs/halt.html#halt-bug may not be implemented.
• OAM Corruption Bug is not implemented.
• Reading and writing VRAM and OAM is successful regardless of LCD mode. https://gbdev.io/pandocs/Accessing_VRAM_and_OAM.html#accessing-vram-and-oam

MBC

• Only MBC1, 2, 3, 5, with optional RTC and SRAM, are implemented. Other memory bank controllers, such as MMM01, MBC6, MBC7, POCKET CAMERA, BANDAI TAMA5, HuC3, HuC1 are not implemented.

[deltabeard]

Updated CGB and RTC branch and issue links.