System self-test

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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).

MVS (SP-E VERSION 0)

Error cram.jpg

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)