System self-test

AES and MVS BIOSes compute their own checksums and compare them against the 16bit value at address $000080. The checksum is a simple byte sum of the whole ROM except locations $000080 and $000081.

= AES =

Screen color meanings (information by Channelmaniac):
 * Blue: All tests passed (The AES does not test the Z80 sound IC).
 * Red: Work RAM error ($100000 region).
 * Green: Palette RAM error ($400000 region).
 * Yellow: Video RAM error (programmed through custom port).
 * Pink: BIOS selfcheck error (0xC00000 region).
 * Cyan: Memory card error (only tested if card in unit and blank).

= MVS (SP-E VERSION 0) =

Here's a tip from a former SNK employee:

Power up the MVS board without a cartridge installed. Look at the border color around the edge of the crosshatch screen. The color will reflect the region the BIOS is for.

Green: 6 slot, an older BIOS Light Blue: USA BIOS, labeled SPU2 Dark Blue: Spanish BIOS, labeled SPS2 Red: Japanese BIOS, labeled SPJ2

Check order ?

Possible errors:
 * WORK RAM ERROR (68k RAM)
 * BACKUP RAM ERROR (Battery-backed RAM)
 * COLOR RAM BANK0 ERROR (First bank of 256 palettes)
 * COLOR RAM BANK1 ERROR (Second bank of 256 palettes)
 * VIDEO RAM ERROR (VRAM)
 * CALENDAR ERROR
 * SYSTEM ROM ERROR (BIOS ROM checksum fail)
 * MEMORY CARD ERROR
 * Z80 ERROR (no reply to sound command $01)