Editing Atari XE Game System (section)

== Technical Specifications ==

The XEGS is internally identical to the Atari 65XE computer and shares the same custom chipset used across all Atari XE-series machines.

=== Processor ===

The XEGS uses the '''MOS Technology 6502C''' (SALLY) microprocessor, a modified version of the 6502 with additional bus control features required by the Atari architecture. It runs at:
* '''1.79 MHz''' (NTSC systems)
* '''1.77 MHz''' (PAL systems)

The SALLY variant includes a HALT input that allows the ANTIC chip to steal bus cycles for direct memory access (DMA) during display generation.

=== Custom Chipset ===

<templatestyles src="Template:StyledTable/styles.css" />
{| class="wikitable styled-table" style="width:100%; text-align:center;"
|+'''XEGS Custom Chipset'''
! Chip !! Function !! Package !! Key Features
|-
| '''ANTIC''' (C021697) || Display controller || 40-pin DIP || Generates display list DMA, handles playfield graphics modes 2–15, horizontal/vertical scrolling, display list interrupts (DLI)
|-
| '''GTIA''' (C014805) || Graphics/colour processor || 40-pin DIP || Player/missile (sprite) graphics, colour processing, 16 colours from 256-colour palette, console key inputs (Start/Select/Option)
|-
| '''POKEY''' (C012294) || Sound and I/O || 40-pin DIP || 4-channel audio, keyboard scanning, serial I/O (SIO bus), timer/IRQ generation, paddle input, random number generator
|-
| '''FREDDIE''' (C061991) || Memory controller || 28-pin DIP || DRAM multiplexing and refresh, address bus control, replaces discrete multiplexers used in earlier XL models
|-
| '''PIA''' (6520) || Peripheral interface || 40-pin DIP || Joystick port I/O, peripheral control lines
|-
| '''MMU''' (C061618) || Memory management || 20-pin DIP || Address decoding, bank select, ROM/RAM mapping
|}

=== Memory ===

* '''64 KB DRAM''' — Eight 4464 (64K×4) DRAM chips (unlike the 65XE's eight 4164 chips, the XEGS board uses 4464s in some revisions)
* '''24 KB ROM''' — Operating system (Rev. 4), Atari BASIC Rev. C, and built-in Missile Command game
* ROM is active when the keyboard is attached; without keyboard, only the OS and Missile Command ROMs are mapped

=== Video Output ===

* '''Composite video''' via RCA jack
* '''RF modulated output''' via RCA jack (channel 2/3 switchable)
* Resolution: up to 320×192 pixels (Graphics 8), 384×240 with overscan
* Text: 40 columns × 24 rows
* 16 simultaneous colours from a palette of 256 (128 hues × 8 luminances on NTSC)
* Hardware scrolling, player/missile graphics (sprites)

=== Audio ===

* '''POKEY''' chip provides 4 independent audio channels
* 8-bit resolution per channel
* Frequency range approximately 30 Hz to 56 kHz (audible range)
* Noise generation, high-pass filter capability
* Two channels can be combined for 16-bit resolution