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(Locations refer to the 2-port version, these may be different on the 4-port model.)

A1 4050
Video signal buffer

A2 C014806 CPU 6502C

This is a custom version of the standard 6502 microprocessor. It is functionally identical to a standard 6502, except that hardware has been added to it that allows the ANTIC chip to do Direct Memory Access (DMA).

A3 C012296 ANTIC

This chip is a microprocessor that reads data directly from RAM to determine how the screen should be drawn and controls the GTIA to actually generate the graphics. The ANTIC is also responsible for processing NMI's.

A5 C014805 GTIA

This chip is responsible for generating the video signal to the TV, generating sprites, reading the joystick trigger buttons, and controlling the reading of the joysticks and keypads (the actual reading is done by POKEY).

A6 74LS139

Address decoding.

A7 C012294 POKEY

This chip is responsible for generating sound, reading the position of the joystick, reading the keypad buttons, processing IRQ's and, controlling the serial I/O port which is accessible through the expansion connector.

A8 C019156A ROM BIOS

This is a 2K ROM chip that holds the character set and the BIOS software. The BIOS initializes the system and to service interrupts.

A9,10,11 4052

Keypad scanning multiplexers.

A14 74LS125

Control signal buffering.

A15 74LS51

DRAM control signals.

A16,17 74LS258

DRAM address multiplexers.

A18-25 MK4516 1x16K DRAM

A26 4013

Power on/off switch latch.

A27 74LS00

Miscellaneous logic.


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