1.12) What is the internal layout of the 8-bit Atari?

ASCII art by Thomas Havemeister.

                  ->                    
+---------------------------------------+
|            +------------+             |
|            | CPU (6502) |         +-------+
|            +------------+      <- |  I/O- |
|                  |     +----------|release|
|                 +-+    |          +-------+
| +---------+<-   |p|    |               |
| |   MMU   |-----| |    | <-+---------+-|----------+----------+
*-| memory- |     |r|    *---|   PIA   | | (trigger)|Controller|====\
| |managment|-----|-+--------| (6520)  | |+---------|   Ports  |====/
| +---------+<-   |o| -> |   +---------+-|-+  <-->  +----------+
|                 | |    |               |||           |    |
|   +-----+       |c|    | <-+---------+ |||           |(lightpen)
|   | RAM |<-A/D  | |    *---|  ANTIC  | |||           |    |
*---|8-128|-------|e|----|---|(2nd CPU)|---------------+    |
|   |Kbyte|->D    | | -> |   +---------+ ||| +---------------
|   +-----+       |s|    |       ||      ||| |
|                 | |    | <-+---------+-|||--------+(screen)
|  +-------+      |s|    *---|  GTIA   |-|+| |      |
|  | Atari |<-A   | |----|---|  /CTIA  | | | | +----------+   +-----------+
|  | BASIC |------|o| -> |   +---------+ | | | | summary  |===| modulator |
*--|8 Kbyte|->D   | |    |               | | | |connection|===| ^^^^^^^^^ |
|  |  ROM  |      |r|    | <-+---------+ | | | +----------+   +-----------+ 
|  +-------+      | |    +---|  POKEY  |-|-|-+      |(sound)        |
|                 | |--------|         |-|-|--------+               |
|  +-------+      |b| ->     +---------+ | +----------+             |
|  |AtariOS|<-A   | |                 |  |            |             |
*--|10/16Kb|------|u|                 +--|----------+ |         tv/monitor
|  |  ROM  |->D   | +-----------------   |          | |         **********
|  +-------+      |s|              | |   |          | |
|                 | |              | |   |          | |
|                 +-+              +-+   |          | |
|                  |                |    |          | |
+--------------*---|------------*---|    |          | |
               |   |            |   |    |          | |
             +-----------+    +-----------+    +------------+
             |ParallelBus|    | Cartridge |    |   Serial   |
             |Interface/ |    |   Slot    |    |Input/Output|
             | Enhanced  |    |    ROM    |    |    (SIO)   |
             | Cartridge |    +-----------+    +------------+
             | Interface |          |                |
             +-----------+          |                |
                   |                |                |
        - memory expansion    -cartridge with   - disk drive
        - Z80 card             programs         - printer
        - 80 char card         (games , dos )   - modem

NOTES
 * RAM: 400/800: 8K, 16K or 48K standard
        600XL:16K standard
        1200XL/800XL/65XE/800XE/XEGS: 64K standard
        130XE:128K standard
 * ROM: 400/800:10K OS, 1200XL:16K OS, all others:16K OS + 8K Atari BASIC
 * CPU: 400/800:6502B, all others:6502C/SALLY
 * 800 includes two Cartridge Slots, all others include one
 * early release 400/800 have CTIA instead of GTIA
 * 400/800 have 4 Controller Ports, all others have 2
 * PBI is on 600XL/800XL only
 * ECI is on 130XE/800XE/some 65XE only
 * Some late XE's use a 68B21 for PIA; PIA is 6520/6520A on all others

Top Document: Atari 8-Bit Computers: Frequently Asked Questions
Previous Document: 1.11) What are the SALLY, ANTIC, CTIA/GTIA, POKEY, and FREDDIE chips?
Next Document: 1.13) Who designed the Atari 8-bit computers?

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Last Update July 24 2008 @ 00:12 AM