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 (all versions ?)

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 checksum error (0xC00000 region).
• Cyan: Memory card error (only tested if card in unit and blank).

Note; the Universe BIOS does not use the above color code system to show errors on AES hardware.

MVS (SP-E VERSION 0)

Information by Channelmaniac:

When a MVS board is powered up without a cartridge installed, the border color around the edges of the crosshatch screen indicates the BIOS region:

• Green: 6 slot, an older BIOS
• Light blue: USA BIOS, labelled SPU2
• Dark blue: Spanish BIOS, labelled SPS2
• Red: Japanese BIOS, labelled 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)