System self-test

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

Checks order ?

=Cartridge systems=

Information by Channelmaniac.

The UniBios case
The Universe BIOS does not use the above color codes to indicate errors.

MVS checks
Additionnal checks are performed on MVS systems:


 * Backup RAM: BACKUP RAM ERROR (Battery-backed RAM)
 * RTC chip: CALENDAR ERROR
 * Z80: Z80 ERROR

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


 * Green: 6 slot (ROM name ?)
 * Cyan: USA, SPU2
 * Blue: Spanish, SPS2
 * Red: Japanese, SPJ2