ogamespec / oammap

A small utility for creating a visual map of the PPU OAM

OAMMap

A small utility for creating a visual map of the PPU OAM.

The map is presented as a set of squares, each square corresponds to one physical location of a memory cell on the chip.

The cells are color coded:

• LimeGreen: Byte 0 (Y)
• Ivory: Byte 1 (Index)
• Red: Byte 2 (Attr)
• Blue: Byte 3 (X)
• DarkViolet: Bytes for Temp OAM ( common color)

Inside each cell is a caption, of the form AA-B:

• AA: Cell address 00-FF
• B: The bit number of the corresponding byte.

Note that the OAM physically lacks cells for bits 2-4 attribute bytes (Byte 2). However, Temp OAM has a place for them, but zeros are always copied there.

NTSC vs PPU

One of the distinguishing features in the NTSC version of the PPU is that the OAM address is fed in inverted form (/OAM0-7). This causes the logical column numbers to no longer correspond to their physical location.

The PPU developers also took this feature into account to connect rows for bits 2-4:

(NTSC PPU to the left)

How to view the map

The utility creates an .xml file, which should be opened in the Deroute utility (File -> Add entities...)

https://github.com/emu-russia/psxdev/releases

Pre-made OAM Maps

⚠️ The pictures are big.

NTSC OAM Map	PAL OAM Map