Visual Diagnostics (Neo Geo AES)
The default BIOS of the Neo Geo AES has some built in basic diagnostics.
Turn on the console, without a game, and if you see a solid colour screen then it indicates the possible cause.
- īģŋBlue = All tests passed (The AES does not test the Z80 sound IC).
- īģŋRed = Work RAM error (0x100000 region).
- īģŋGreen = Palette RAM error (0x400000 region).
- īģŋYellow = Video RAM error (programmed through custom port).
- īģŋMagenta = BIOS self-check error (0xC00000 region).
- īģŋCyan = Memory card error (only tested if card in unit and blank).
If you get glitched pixels without any sign of actual game data (no moving graphics or logos where you would expect) without a game, with a game, with diagnostics ROM (they all act the same) this is slight under voltage on the 5V rail or excessive noise on the power rai
If you can clearly see the console loading as you might expect, but in place of where graphics would be, you get garbled pixels or repeating pixels, it is often the CXK5814P video RAM attached to the LSPC, or traces to and from them.
It could also be the other CXK58257AM video RAM also attached to the LSPC.
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To get better diagnostics
