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Amiga_Info.
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1992-03-19
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Screen Colours
Each time your computer is turned on the screen colours are
indicating what is happening inside your computer. The colours
displayed are as follows:
DARK GRAY - The testing phase of the CPU for the 680x0 chip.
LIGHT GRAY - The software is loading without problems.
WHITE - All initialization tests have passed.
Any problems will produce a different screen colour, and possible
screen colours are as follows:
RED - A ROM checksum error.
GREEN - A chip RAM error.
BLUE - One of the Amiga's custom chips has a problem.
YELLOW - A 680x0 error was discovered before a GURU was started.
GREEN - A Agnus chip problem, the most common being a loose chip.
Caps Lock Flashes
The small light located in the top of the Caps Lock key can also
indicate a problem. The number of flashes indicate as follows:
ONE - Keyboard ROM checksum failure.
TWO - Keyboard RAM test failure.
THREE - Keyboard watchdog timer test failure.
FOUR - A short between or on one of the seven special keys
(currently not implemented).
Amiga Chips and What They Do
The Amiga has some special chips which makes the Amiga unique. They
are as follows Paula, Agnes and Denise.
Paula, is the audio chip which handles digital to analog sound
conversions (four voices). Also the Paula handles many of the
input/output tasks, examples are disk and interrupt controls, mouse
and joystick ports and the serial port.
Agnes, is the graphics, and the DMA (Direct Memory Access) chip.
Part of the graphics is the Blitter and Copper. The Blitter
coprocessor chip quickly draws and manipulate lines and rectangular
parts of graphic images. Copper, a part of the Agnes which
synchronizes the screen image and the graphic requests. DMA, a
controller for the different chips for system memory uses. Writing
and reading is directed to the proper location, instead of the memory
being allocated through CPU instructions.
Denise or Video Coprocessor Chip, assists the 68000 with screen
control functions, and handling screen displays and sprites.
Information Sources
Amiga World, Technical Reference Guide, Special Edition 1987
Amiga World, Tech Journal, Start-up Messages, Aug/Sept. 1991
CBM, Service Manual, A1000 Component Level Repair PN314038-02
George R. Skinner
May 5, 1992