OFFICIAL FAQ
1.13) What is the internal hardware arrangement of the 8-bit Atari?
+---------+ +-+ +---------+
| 6502 | |p| | ANTIC +-<--- Controller Ports: Light Pen/Light Gun
| MPU +---+ +-----+ |
+---------+ |r| +-+-------+ +- Controller Ports: Triggers
| | +->-+ +---<-+ (Joystick/Driving/Trackball Triggers)
+---------+ |o| +-----+-+-+-<--- Console Switches (Start/Select/Option)
| RAM +---+ | |CTIA/GTIA+--->- Picture Output (to TV/Monitor)
|---------| |c+-----+ /FGTIA +--->- Sound Output (to TV/Monitor)
| 8-48KiB | | | +-----+---+--->- Console Speaker / to Sound Output
| /64KiB | |e| +->-+
| /128KiB | | | +-+-------+
+---------+ |s| | POKEY +-<--- Keyboard
| +-----+ +-<--- Controller Ports: Potentiometer Ports
+---------+ |s| +-------+-+ (Paddles, Touch Tablet)
| ROM +->-+ | +-<SIO>+ Program Recorder
|---------| |o| +-------+-+ | + Disk Drives
| OS | | | | 6520 | | + Printers
|10/14KiB | |r+-----+ PIA | | + Modem
|---------| | | +-------+-+ | + 850 Interface
| BASIC | | | | +->- to Sound Output
| 8KiB | |b| |
|---------| | | +------+ Controller Ports: Data Bits (Joysticks,
| Missile | |u| Paddle Triggers, Light Pen Button,
| Command | | | Driving, Touch Tablet Buttons,
| 8KiB | |s| Trackballs, Light Gun Trigger, XEP80)
|---------| +-+-----------<PBI/ECI>+ 1064 Memory Module (600XL) (48KiB RAM)
|cartridge+-----------------------<--- Left Cartridge (8KiB/16KiB ROM)
|0/8/16KiB+-----------------------<--- Right Cartridge (8KiB ROM)
+---------+
NOTES
* 6502 MPU: Most NTSC 400/800: MOS Technology MCS6502A or equivalent
Late NTSC 400/800, all PAL 400/800, and all XL/XE: Atari SALLY
* ROM: 400/800: 10KiB 400/800 OS
1200XL: 14KiB XL OS
600XL/800XL/65XE/130XE/800XE: 22KiB (14KiB XL OS + 8KiB BASIC)
XEgs: 30KiB (14KiB XL OS + 8KiB BASIC + 8KiB Missile Command)
* RAM: 400: 8KiB or 16KiB, or 48KiB with 48K RAM Expansion Kit
800: 8KiB-48KiB using 1-3 CX852 8K RAM or CX853 16K RAM Memory Modules
600XL: 16KiB, or 64KiB with 1064 Memory Module
1200XL/800XL/65XE/800XE/XEgs: 64KiB
130XE: 128KiB
* CTIA: Earlier NTSC 400/800
GTIA: Later NTSC 400/800 and all NTSC/PAL XL/XE
FGTIA: SECAM XL/XE
* Right Cartridge: 800 only
* Controller Ports: 400/800 have 4; XL/XE have 2
* Controller Port Triggers: Not connected to ANTIC on jacks 1-3 on the 400
* Console Speaker: 400/800: An internal physical speaker
XL/XE: Mixed into Sound Output to TV/Monitor
* PBI: 600XL/800XL only
* ECI: 130XE/65XE(later)/800XE only