You may notice that when you turn on or reset your Amiga a few different colours flash by. These actually mean something. Here you go:
RED Bad ROM YELLOW CPU Exception Before Bootstrap Code is Loaded GREEN Bad Chip RAM BLACK No CPU WHITE Expansion passed GREY CPU Passed Constant white is failure of CPU. Or as taken from the Amiga 4000 Service Manual: Passed Test Light Grey Initial hardware configuration tests passed. Initial system software tests passed. Final initialization test passed. Failed Test Red ROM Error - Reseat or replace Green CHIP RAM error (reset AGNUS and re-test) Blue Custom Chip(s) Error Yellow 68000 detected error before software trapped it (GURU) The system performs the following test sequence: 1. Delays beginning the tests a fraction of a second to allow the hardware to stabilize. 2. Jumps to ROM code in diagnostic card (if found) 3. Disables and clears all DMA and interupts. 4. Turns on the screen. 5. Checks the general hardware configuration. If the screen remains a light gray colours and the tests continue, the hardware is OK. If an error occurs, the system halts. 6. Performs checksum test on ROMs. If the system fails the ROM test, the screen display turns red and the system halts.
KeyboardOne Blink ROM Checksum failure Two blinks RAM test failed Three Blinks Watchdog timer failed Four blinks A short exists between two row lines or one of the seven special keys (not implemented) Five Blinks Your keyboard has become nuclear. RUN!