Editing Atari 600XL

{{Infobox computer
| name         = Atari 600XL
| image        = [[File:Atari-600XL.jpg|250px]]
| caption      = Atari 600XL home computer
| manufacturer = Atari, Inc.
| type         = Home Computer
| release date = 1983
| discontinued = 1984
| price        = US$199 (1983)
| cpu          = MOS Technology 6502C (SALLY) @ 1.79 MHz (NTSC) / 1.77 MHz (PAL)
| memory       = 16 KB RAM (expandable to 64 KB), 24 KB ROM
| storage      = External cassette tape, optional 5.25" floppy disk drive (Atari 1050)
| display      = 320×192 pixels (max), 40×24 text, 16 colours (ANTIC/GTIA)
| sound        = POKEY: 4 voices, 8-bit mono
| dimensions   = 26.7 cm × 21.6 cm × 7.6 cm (10.5" × 8.5" × 3")
| weight       = 1.2 kg (2.6 lbs)
| os           = Atari OS Rev. 1, Atari BASIC Rev. B (in ROM)
| predecessor  = [[Atari 400]]
| successor    = [[Atari 800XL]]
| codename     = Surely
| model        = 600XL
}}

The '''Atari 600XL''' is a home computer released by Atari, Inc. in 1983 as the entry-level model of the XL series within the [[Atari 8-bit Family|Atari 8-bit family]]. Designed as a budget-friendly companion to the [[Atari 800XL]], the 600XL featured a smaller case, a membrane keyboard, and only 16 KB of RAM — half of what was needed to run many commercial programs of the era. Despite its limitations, the 600XL shared the same custom chipset and was fully expandable to 64 KB via the Atari 1064 memory module or third-party upgrades.

== History ==
The 600XL was developed under the internal codename '''"Surely"''' as part of Atari's effort to replace the ageing [[Atari 400]] and [[Atari 800]] with a more cost-effective product line. Announced at the Summer Consumer Electronics Show (CES) in June 1983, the 600XL was positioned against the Commodore VIC-20 and Sinclair ZX Spectrum in the low-end market, while the 800XL targeted the Commodore 64.

At a retail price of US$199, the 600XL was significantly cheaper than the $299 800XL. However, its 16 KB RAM limitation proved to be a critical shortcoming — many Atari 8-bit programs required 48 KB or more to run, making the 600XL unable to use much of the existing software library without a memory upgrade.

Production of the 600XL was discontinued in 1984 after Jack Tramiel's acquisition of Atari, as the model was deemed unprofitable. Total production of both the 600XL and 800XL in 1983 was approximately 400,000 units combined.

== Architecture and Processor ==
The 600XL is powered by the '''MOS Technology 6502C''' microprocessor (designated "SALLY" by Atari, part number C014806), running at:
* '''1.79 MHz''' (NTSC systems)
* '''1.77 MHz''' (PAL systems)

The SALLY variant of the 6502 includes a HALT line that allows the ANTIC chip to pause the CPU during screen rendering for direct memory access (DMA), a feature unique to Atari's implementation.

The CPU is supported by Atari's custom chipset:
* '''ANTIC''' (C012296) – Alphanumeric Television Interface Controller. A programmable co-processor that generates display lists and handles graphics modes independently of the CPU.
* '''GTIA''' (C014805) – Graphics Television Interface Adapter. Manages colour output, player/missile graphics (sprites), and collision detection. An evolution of the earlier CTIA chip.
* '''POKEY''' (C012294) – Pot Keyboard Integrated Circuit. Provides four-channel audio, keyboard scanning, serial I/O (SIO) control, paddle input, and random number generation.
* '''PIA''' (6520) – Peripheral Interface Adapter. Handles parallel I/O for joystick ports and peripheral control lines.

This architecture is identical to the 800XL, giving the 600XL the same graphics, sound, and I/O capabilities despite its lower price point.

== Memory ==
The Atari 600XL ships with:
* '''16 KB RAM''' – provided by either two 4164 (64K×1) DRAM chips or a single 4416 (16K×4) DRAM chip, depending on the board revision.
* '''24 KB ROM''' – split across two ROM ICs: a 16 KB OS ROM (Atari OS Rev. 1) and an 8 KB Atari BASIC Rev. B ROM.

The 16 KB RAM limitation is the 600XL's most significant drawback. Many commercial programs and games require a minimum of 48 KB to operate, rendering them incompatible without expansion. Atari addressed this with the '''Atari 1064 Memory Module''', an external unit that plugged into the PBI port on the rear of the 600XL to expand RAM to 64 KB. Third-party upgrades also became available, including internal modifications that replaced or supplemented the existing DRAM chips with 4464 or 4164 ICs to achieve 64 KB.

== Input/Output and Expansion ==
The 600XL provides the following ports and connectors:
* '''Cartridge slot''' – standard Atari 8-bit cartridge port on top of the unit
* '''SIO (Serial Input/Output) port''' – for daisy-chaining disk drives, cassette recorders, printers, modems, and other Atari peripherals
* '''Parallel Bus Interface (PBI)''' – a 50-pin edge connector on the rear, providing direct access to the system bus for memory expansion and high-speed peripherals
* '''2 × Joystick ports''' – DE-9 connectors compatible with Atari-standard joysticks and paddles
* '''Composite video output''' – for connection to a monitor (active on some revisions)
* '''RF modulator output''' – for connection to a television via the antenna input
* '''Power input''' – barrel connector for external +5V DC power supply

The PBI is the 600XL's most notable expansion feature, providing a direct connection to the address bus, data bus, and control lines. This allowed peripherals like the Atari 1064 Memory Module to expand the system's capabilities beyond its base configuration. However, relatively few PBI peripherals were commercially produced.

== Keyboard ==
The 600XL uses a '''membrane keyboard''' with a rubber dome design, similar in feel to the earlier Atari 400 but with individual key caps that provide better tactile feedback. The keyboard includes 62 keys with the standard Atari 8-bit layout, including function keys and the HELP, START, SELECT, OPTION, and RESET keys.

The keyboard is controlled by two '''CD4051''' analogue multiplexer ICs (U22 and U23) which scan the key matrix in conjunction with the POKEY chip. Keyboard failures are commonly caused by degradation of these multiplexer ICs or contamination of the membrane contacts.

== Display and Graphics ==
Graphics capabilities are identical to the [[Atari 800XL]], handled by the ANTIC and GTIA chips:
* '''Resolution:''' up to 320×192 pixels in bitmap mode
* '''Text:''' 40 columns × 24 rows (Graphics Mode 0), with additional modes supporting 20 and 80 columns
* '''Colours:''' up to 16 on screen simultaneously from a palette of 256 (16 hues × 16 luminance levels)
* '''Player/Missile Graphics:''' 4 players and 4 missiles (hardware sprites), with automatic collision detection
* '''Display List:''' programmable display architecture allowing mixed-mode screens and smooth scrolling

== Sound ==
Audio is generated by the '''POKEY''' chip:
* '''4 independent voices''' (channels), each with 8-bit frequency resolution
* Programmable volume (4-bit), frequency, and distortion per channel
* Channels can be linked in pairs for 16-bit frequency resolution
* White noise generation for sound effects
* High-pass filter capability when channels are linked

== Power Supply ==
The 600XL uses the same external power supply as the 800XL, providing '''regulated +5V DC''' through a barrel connector. The original Atari power supply (Atari CO61982) is rated at +5V, 1.5A. The system draws approximately 800mA under normal operation.

== Comparison with the Atari 800XL ==
<templatestyles src="Template:StyledTable/styles.css" />

{| class="wikitable styled-table" style="width:80%; text-align:center;"
|+'''600XL vs 800XL Comparison'''
|-
! Feature !! Atari 600XL !! Atari 800XL
|-
| '''RAM''' || 16 KB || 64 KB
|-
| '''Price (1983)''' || US$199 || US$299
|-
| '''Keyboard''' || Membrane || Full-stroke mechanical
|-
| '''Case Size''' || Compact (26.7 × 21.6 cm) || Standard (40.6 × 24.1 cm)
|-
| '''PBI Port''' || Yes || Yes
|-
| '''CPU''' || 6502C @ 1.79 MHz || 6502C @ 1.79 MHz
|-
| '''Custom Chips''' || ANTIC / GTIA / POKEY || ANTIC / GTIA / POKEY
|-
| '''ROM''' || 24 KB (OS + BASIC) || 24 KB (OS + BASIC)
|-
| '''Cartridge Slot''' || Yes || Yes
|-
| '''SIO Port''' || Yes || Yes
|}

== Known Revisions ==
Several board revisions of the 600XL are documented:
* '''NTSC Chelco Rev. 8A''' – manufactured by Chelco, common in North American units
* '''PAL Rev A''' – standard European PAL version
* '''NTSC Rev D''' – later North American revision

Board revisions may differ in the number and type of RAM chips used, capacitor placement, and minor circuit changes.

== Related Pages ==
* [[Atari 600XL General Maintenance]]
* [[Atari 600XL Troubleshooting Guide]]
* [[Atari 600XL Capacitor Replacement Guide]]

[[Category:Atari Systems]]

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