XPost: comp.sys.atari.8bit, news.answers

Archive-name: atari-8-bit/faq
Last-modified: July 9, 2020

Welcome to the comp.sys.atari.8bit newsgroup!

Atari 8-Bit Computers

Frequently Asked Questions List
___________ _______________
| ///////// | _____________ | ||||||||||| |
|___________| | | | ||_______|| |
|______/////| |____[---]____| | / _________ \ |
|LLLLLLLLLLL| |LLLLLLLLLLL || | LLLLLLLLLLL L |
|LLLLLLLLLLL| |LLLLLLLLLLL || | LLLLLLLLLLL L |
|__[_____]__| |__[_____]____| |___[_____]_____|
130XE 800XL 800
___________ __---------__
| ///////// | | / _____ \ |
|___________| _____________ | / |_____| \ |
|______/////| |____[---]____| | ___________ |
|LLLLLLLLLLL| |LLLLLLLLLLL || | ========== =|
|LLLLLLLLLLL| |LLLLLLLLLLL || | ========== =|
|__[_____]__| |__[_____]____| |___[_____]___|
65XE 600XL 400
___________ _____________
| ///////// | ___________ | |
|___________| |/// / | | |
|______/////| |// / | /\___________ |=============|
|LLLLLLLLLLL| |/O\ |\/ |LLLLLLLLLLL| | LLLLLLLLLLL |
|LLLLLLLLLLL| |-----------| |LLLLLLLLLLL| | LLLLLLLLLLL |
|__[_____]__| |____O_O_O_O| |__[_____]__| |___[_____]___|
800XE XE game system 1200XL

Additions/suggestions/comments/corrections are needed! Please send to:

Michael Current, michael@mcurrent.name

Copyright (c) 1992-2020 by Michael D. Current, and others where noted. Feel free to reproduce this file, in whole or in part, so long as the content of that portion reproduced is not modified, and so long as credit is given to
this FAQ list or its Maintainer, or the author of that section reproduced
when given.

This document is in a constant state of development and comes with no guarantees. If you see any problems, I need to hear from you!

Special thanks to Laurent Delsarte for his numerous suggestions/comments/ corrections for this FAQ list over many years.

The latest version of this document is irregularly posted to these Usenet newsgroups: comp.sys.atari.8bit, comp.answers, news.answers

It is also kept at: https://mcurrent.name/atari-8-bit/faq.txt
Enhanced versions (Text, A4 PDF, US Letter PDF): http://www.atari800xl.eu/

You may also request my latest working version at: michael@mcurrent.name

UPDATES SINCE PREVIOUS POSTING:
2020.07.09 3.1.2 NA-R25 added
2020.07.09 1.7 65XE Najm version package
2020.07.09 7.1.1 Arabic OS two versions
2020.07.09 3.2.3 different suggested explanation for XF551 destroying disks 2020.07.07 6.12 Compy-Shop, Megaram, Turbo-Freezer additions/fixes, and
many other enhancements/corrections
2020.06.21 11.1 added missing Robotron release
2020.06.21 References to many tfhh upgrades added throughout
2020.06.21 3.3.5 add Ultimate Cart and Uno Cart
2020.06.18 9.1 .A2R Applesauce file format
2020.06.18 10.2 Applesauce
2020.06.16 7.3.1 intro revisit, especially regarding the Resident Disk Handler 2020.06.14 1.16 1200XL/600XL/800XL revisit
2020.06.12 10.2 added a8rawconv
2020.06.12 9.1 section revisit. Many corrections and updates.
2020.06.11 4.2 1027 specs revisted, corrected
2020.06.11 spell out all instances of MCU
2020.06.10 1.4 Auto RAM/ROM check at boot, thanks Laurent Delsarte
2020.06.08 10.2 Greaseweazle and Greaseweazle F7 Plus
2020.06.08 10.1 10.2 10.3 sections divided, re-titled
2020.06.06 3.2.1 3.2.2 RPM spec ranges spelled out, thanks Laurent Delsarte 2020.06.03 Duplicating Technologies revisit
2020.06.01 7.3.4 OS/A+ 2.1 verified, thanks Roland Wassenberg
2020.05.31 4.3 uPD7811 in the XMM801
2020.05.31 1.9 1.7 XEgs packages complete revisit
2020.05.31 6.3/6.4 controllers/kits section overhauled/split in two
2020.05.29 11.1 Rosenthal and especially Mayer revisits
2020.05.29 4.2 4.3 self tests, thanks Laurent Delsarte for idea
2020.05.25 2.2 RF Channel 4 was Channel B in Italy
2020.05.16 1.8 3.1.1 130XE Starter Pack revisit
2020.05.16 4.2 1.5 AtariWriter System revisit
2020.05.16 6.3 11.1 Programming System never shipped (misidentified photo) 2020.05.14 eliminate virtually all instances of MPU and CPU, which are
arbitrary terms; replace with "microprocessor" usually
2020.05.10 1.1 Atari joystick port discussion
2020.05.10 11.1 spring 1983 software release dates
2020.05.10 1.5 1.6 Connection Instructions revisted
2020.05.09 throughout: removed "CO" Atari part number variations which only
reflected typography errors by Atari -- C0 is the correct variation 2020.05.09 1.7 Medalist Dart Star dart boards
2020.05.02 3.2.2 US Doubler - sold with or without SpartaDOS Construction Set 2020.05.02 4.1 825 pinout and other tweaks
2020.05.02 8.3 ACE-80 tweaks
2020.04.30 7.3.2 SDFS 2.0 and 2.1 revisit
2020.04.29 7.3.4 SpartaDOS filesystem 1.1 and 2.0 revisit
2020.04.26 11.1 revisit some summer82-winter83 release dates (including
Atari Speed Reading; history of Home Manager kit)
2020.04.21 1.7 1.8 1.10 manuals
2020.04.19 11.1 1.16 updates using newly-available info at
http://www.atarimuseum.com/computers/8BITS/XE/xesystems.html 2020.04.18 11.1 much work using the Atari Telephone Directory of 1/20/84 2020.04.12 11.1 1979 May & June, and especially January 1980 show revisits 2020.04.08 7.3.2 SpartaDOS X 4.49 with Toolkit (7 Apr. 2020)
2020.03.29 standardize Port B banked memory references
2020.03.28 standardize RAMdisk generic term -> RAM drive
2020.03.28 7.1.2 QMEG-OS V3 revisit, QMEG+OS 4.04 revisit
2020.03.28 throughout: standardize Axlon banked memory references
2020.03.27 6.12 Integrater RAM drive clarification
2020.03.27 6.11 7.3.4 standardize Mosaic 64K RAM Select references

------------------------------

Subject: 0.1) Table of contents

0.1) Table of contents

Computers
1.1) What is an Atari 8-bit computer?
1.2) What is the Atari 400?
1.3) What is the Atari 800?
1.4) What is the Atari 1200XL?
1.5) What is the Atari 600XL?
1.6) What is the Atari 800XL?
1.7) What is the Atari 65XE?
1.8) What is the Atari 130XE?
1.9) What is the Atari XE game system?
1.10) What is the Atari 800XE?
1.11) What were the Atari 1400XL, 1450XLD, 65XEP, and 65XEM?
1.12) What are SALLY, ANTIC, CTIA/GTIA/FGTIA, POKEY, and FREDDIE?
1.13) What is the internal hardware arrangement of the 8-bit Atari?
1.14) What is the Atari memory map and how is banked memory managed?
1.15) What are the pinouts for the various connectors on the Atari?
1.16) Who designed the Atari 8-bit computers?
1.17) How do I use my Atari computer system?

Televisions, Monitors, Speakers
2.1) What are analog TV broadcasting systems and composite video?
2.2) What kinds of TVs can display my Atari's RF output signal?
2.3) What kinds of computer monitors can I use with my Atari?
2.4) What were the Atari XC1411 and XM128 monitors?
2.5) What are composite video artifact colors, or artifacts?
2.6) What is HDTV display lag?

Mass Storage: Compact Cassette Players/Recorders
3.1.1) What are the Atari 410, 1010, XC11, & XC12 Program Recorders?
3.1.2) What other cassette recorders can I use with my Atari?
3.1.3) What speed upgrades are there for Atari program recorders?

Mass Storage: Floppy Disk Drives
3.2.1) What is the Atari 810 Disk Drive?
3.2.2) What is the Atari 1050 Disk Drive?
3.2.3) What is the Atari XF551 Disk Drive?
3.2.4) What were the Atari 815, XF521, and XF351 Disk Drives?
3.2.5) What other floppy disk drives were designed for my Atari?
3.2.6) What is the Percom configuration block?
3.2.7) How can I use an industry standard floppy disk drive?

Mass Storage: High Capacity Media
3.3.1) What is the Corvus disk system?
3.3.2) How can I use an ST506 interface hard disk (MFM or RLL)?
3.3.3) How can I use a SASI or SCSI interface hard disk?
3.3.4) How can I use an IDE interface hard disk or CompactFlash card?
3.3.5) How can I use a Secure Digital (SD) card with my Atari?
3.3.6) How can I use a USB flash drive with my Atari?

Printers
4.1) What are the Atari 820, 822, and 825 Printers?
4.2) What are the Atari 1020, 1025, 1027, and 1029 Printers?
4.3) What are the Atari XMM801 and XDM121 Printers?
4.4) What were the Atari XTM201 and XTC201 Printers?
4.5) What other printers were designed for my Atari?
4.6) How can I use a Centronics or IBM parallel interface printer?

Modems and other Networking Devices
5.1) What are the Atari 830, 835, 1030, XM301, and SX212 Modems?
5.2) What other modems can I use with my Atari?
5.3) What should I know about using fast modems with the Atari?
5.4) How do I transfer files using a null modem cable?
5.5) What networking hardware is there for the Atari?
5.6) How can I connect my Atari to a high speed/Ethernet network?

Interfaces
6.1.1) What is the Atari 850 Interface Module?
6.1.2) What is the Atari XEP80 Interface Module?
6.1.3) What were the Atari CP/M Module and 1090 XL Expansion System?
6.1.4) What MIDI interfaces are there for the Atari?
6.1.5) How can I use an ISA device with my Atari?
6.1.6) How can I use a USB device with my Atari?
6.1.7) Can the Atari use my other computer's storage/printer/network?

Hardware Upgrades and Accessories
6.2) What are the power requirements for my Atari components?
6.3) What accessories/controllers did Atari make for their computers?
6.4) What Kits/Add-A-Paks did Atari make for their 8-bit computers?
6.5) What graphics tablets were produced for the Atari?
6.6) What light pens were produced for the Atari?
6.7) What light guns were produced for the Atari?
6.8) What voice/speech synthesis hardware is there for the Atari?
6.9) What sound digitizers/samplers were produced for the Atari?
6.10) What sound upgrades (stereo or 8-bit PCM) are there?
6.11) What graphics enhancements are there for the Atari?
6.12) What types of memory upgrades are there for the Atari?
6.13) What personality boards were produced for the Atari 800?

Core Software: OS
7.1.1) What is the Atari Operating System?
7.1.2) What modified versions of the Atari OS were released?
7.1.3) What is the ATASCII (Atari ASCII) encoding standard?
7.1.4) How is the Input/Output subsystem of the Atari OS organized?
7.1.5) What is Attract mode?
7.1.6) What is the Atari cassette utilization/filesystem?
7.1.7) What programs run only on the 400/800 (not the XL/XE) and why?
7.1.8) Why do some programs run only on the XL/XE (not the 400/800)?
7.1.9) How can I run older programs using the Atari Translator?
7.1.10) How can software detect NTSC versus PAL/SECAM computer types?

Core Software: BASIC
7.2.1) What is Atari BASIC?
7.2.2) How do I load/run or save an Atari BASIC program on cassette?

Core Software: DOS
7.3.1) What is Atari DOS, and what versions did Atari release?
7.3.2) What are RealDOS, SpartaDOS X, and XDOS?
7.3.3) What are MyPicoDOS, Micro-SpartaDOS, and LiteDOS?
7.3.4) What other 3rd-party DOS versions were released for the Atari?
7.3.5) What should I know about filenames and filename extensions?
7.3.6) What Atari programs can use MS-DOS 5.25" or 3.5" diskettes?

Core Software: GUI
7.4) Are there Graphical User Interfaces (GUIs) for the Atari?

Core Software: Modem Handlers
7.5) What should I know about R: and T: modem device handlers?

Software
8.1) How may a program behave on NTSC/PAL/SECAM computer versions?
8.2) What programming languages are available for the Atari?
8.3) What cartridges were released for the Right Slot of the 800?
8.4) What games support 4 or more simultaneous players?
8.5) What programs use a light pen or a light gun?
8.6) What programs are designed for a true trackball controller?
8.7) What programs are designed to work with a mouse?
8.8) What programs use paddle controllers?
8.9) What programs include CX85 Numerical Keypad support?
8.10) What programs use: Touch Tablet or KoalaPad/Animation Station?
8.11) What games support online action via modem?
8.12) What programs support Atari computer networking?
8.13) What programs use Keyboard Controllers?
8.14) What programs use Driving Controllers?
8.15) What noncommercial telecommunications programs are there?
8.16) What programs can I use to host a BBS on the Atari?

Atari Media Image Formats
9.1) What file formats for entire disks/tapes/cartridges are there?

For Other Computers
10.1) How can my PC's internal floppy disk drive use Atari diskettes?
10.2) How can my PC with USB floppy disk drive use Atari diskettes?
10.3) How can my PC use Atari diskettes using my Atari disk drive?

Timeline
11.1) What is the history of Atari's 8-bit computers platform?

To do? list:
- Finish building complete parallel interface list
- Build complete RS-232 interface list
THIS INFO TO MOVE TO NEW RS-232 INTERFACE SECTION:
(Datatari / Multi-Viewterm by Miracle Technology, later by
Gralin International, used to access Prestel online service in the UK;
DATARI will open up the full world of VIEWDATA systems including
PRESTEL, TELECOM G0LD and others.
Datatari RS-232 interface, software by Matthew Jones
hardware also supported by the Communications module of Mini Office II
by Database Software (1987)
Digital Devices U-Call Model A
- SIO bus - move info from 1.17 to its own section
- Atari Cartridge
- Diagnostic cartridges, eg Star Raiders, Basketball
- In his Antic Podcast interview, Crane calls bit 7 of the option byte
the "Al Miller bit"
- Boot cartridge/disk/cassette formats
- DOS 2 binary file format
- Commercial telecommunications programs
- programs supporting Axlon or Mosaic banked memory
Axlon list: OmniWriter,
Mosaic list: RAMbrandt
- How can I run CP/M on the Atari?
Note: SDX 4.46+ can read Indus CP/M disks
- Mass Storage: Re-Writable Cartridges
- Persistent RAM by Intra-Tech Computer Products
http://atariage.com/forums/topic/287343-the-persistent-ram-cartridge/

------------------------------

Subject: 1.1) What is an Atari 8-bit computer?

Based in Silicon Valley in the USA, the company known as Atari produced a line of home computers from 1979 to 1992 often referred to collectively as the "Atari 8-bits," the "8-bit Ataris," the "400/800/XL/XE series," etc.

The computers included the 400, 800, 1200XL, 600XL, 800XL, 65XE, 130XE, 800XE, and the XE game system.

For basic marketplace context, here are the release years of the 8-bit Atari computers alongside release years of significant competing home/personal computers. Note: Market dynamics varied substantially around the world.
1977: Apple II, Commodore PET, Radio Shack TRS-80
1978: ARI Cybervision 2001
1979: Atari 400/800, Apple II Plus, Texas Instruments TI-99/4
1980: Radio Shack TRS-80 Model III, TRS-80 Color Computer, Sinclair ZX80
1981: Acorn BBC Micro, Commodore VIC-20, IBM PC, Osborne 1, Sinclair ZX81,
Texas Instruments TI-99/4A
1982: Commodore 64, Kaypro II, Sinclair ZX Spectrum
1983: Atari 1200XL/600XL/800XL, Acorn Electron, Apple IIe, Coleco Adam, MSX,
IBM PC XT, Radio Shack TRS-80 Model 4, TRS-80 Color Computer 2
1984: Amstrad CPC, Apple IIc, Apple Macintosh, IBM PCjr, IBM PC AT
1985: Atari 65XE/130XE, Atari 520ST, Commodore 128, Commodore Amiga
1986: Atari 1040ST, Apple Macintosh Plus, Tandy Color Computer 3
1987: Atari 800XE, Acorn Archimedes, Atari Mega ST, Apple Macintosh II,
Apple Macintosh SE, Commodore Amiga 500, IBM PS/2

1987 also saw the release of the Atari XE game system, competing alongside Atari's own 7800 (released in 1986) and legacy 2600 (available since 1977) systems, and competing directly against the leading home gaming consoles of
the time, the Nintendo Entertainment System and the Sega Master System.

In marketing their computers to the public, Atari always had to contend with their company history and reputation as a maker of video games. While the 8-bit Atari computers in their heyday were technically quite comparable if not superior in the worlds of home and business personal computing, they also live up to the name "Atari" with a huge library of video games which were often outstanding for their time.

The 8-bit Atari computers do not use the same cartridges or floppy disks as
any other Atari platforms, such as the 2600 Video Computer System (VCS), the 5200 SuperSystem, the 7800 ProSystem, or the ST/TT/Falcon computers.

The controller ports of the 8-bit Atari computers are 100% compatible with the joystick ports of the 2600 VCS, allowing controllers to be used with either platform. The Atari 7800 and Atari ST/TT/Falcon also share very similar controller ports, as do the Commodore VIC-20, Commodore 64, Commodore Amiga, Commodore CD32, Amstrad CPC, MSX, Sega Master System, and Sega Genesis/Mega Drive. Simple controllers (single-button joysticks) may work across all of these platforms, while more advanced controllers may work with only a subset
of these systems.

The Atari 5200 hardware platform is very closely related the 8-bit Atari computers, including use of the same custom chipset (SALLY/ANTIC/GTIA/POKEY). Differences in the 5200 include a fixed 16KiB of RAM, fixed 32KiB ROM
cartridge size, physically different cartridge and controller ports, and a
much smaller 2KiB operating system.

Here are some of the hardware performance specifications of the 8-bit Atari computers:

6502 MICROPROCESSOR:
MOS Technology MCS6502A or equivalent (most NTSC 400/800 machines)
Atari SALLY (late NTSC 400/800, all PAL 400/800, and all XL/XE)

6502 CLOCK RATE:
1.789773MHz (NTSC machines; engineering target = 1/2 the standard
NTSC color subcarrier frequency of 315/88 Hz, or
3.57954545MHz)
1.7734475MHz (PAL/SECAM machines; engineering target = 2/5 the PAL
color subcarrier frequency of 4.43361875MHz

COLOR CLOCKS per MACHINE CYCLE
2

MACHINE CYCLES per SCAN LINE
114

COLOR CLOCKS per SCAN LINE
228 (2 color clocks/machine cycle * 114 machine cycles/scan line)

SCAN LINES per FRAME
262 (NTSC machines)
312 (PAL/SECAM machines)

MACHINE CYCLES per FRAME:
29,868 (NTSC machines: 114 machine cycles/scan line * 262 lines/frame)
35,568 (PAL/SECAM machines: 114 cycles/scan line * 312 lines/frame)

FRAME REFRESH RATE:
59.92Hz (NTSC machines) (1.789773MHz / 29,868 cycles/frame)
49.86Hz (PAL/SECAM machines) (1.7734475MHz / 35,568 cycles/frame)

MAXIMUM RESOLUTION = GRAPHICS PIXEL
0.5 color clock (width) x 1 scan line (height)

MAXIMUM HORIZONTAL FRAME RESOLUTION (Standard Playfield)
320 pixels (160 color clocks * 2 pixels/color clock)

MAXIMUM VERTICAL FRAME RESOLUTION (Standard/Narrow/Wide Playfields)
192 pixels (192 scan lines)

MAXIMUM HORIZONTAL FRAME RESOLUTION (Wide Playfield)
352 pixels (176 displayable color clocks * 2 pixels/color clock)

MAXIMUM VERTICAL FRAME RESOLUTION (custom display list)
240 pixels (240 displayable scan lines)

GRAPHICS MODES
The ANTIC chip supports 14 graphics modes (2-F), and the GTIA/FGTIA chip
supports 4 color interpretations for each mode (1 normal and 3 alternate),
for a total of 56 combinations. However, only ANTIC modes 2, 3, and F are
capable of fully expressing the color palettes of the alternate color
interpretations, for a total of 23 distinct fully-functional graphics modes.
(Atari marketing and consumer documentation often only acknowledged the 16
modes supported by the Operating System, referenced as 11 graphics modes and
5 text modes.)
Explore all 56 modes: https://www.atarimagazines.com/v3n5/allmodes.html

ANTIC GTIA AtariOS Display Resolution Colors
Mode Mode + Mode Type screen / each char (Color Registers) ------------------------------------------------------------------------------
2 0 Char 40 x 24 8x8 3 *
2 1 - Char 40 x 24 2x8 16 or 8 **
2 2 - Char 40 x 24 2x8 9
2 3 - Char 40 x 24 2x8 16 ***
3 - Char 40 x 19 8x8 3 *
3 1 - Char 40 x 19 2x8 16 or 8 **
3 2 - Char 40 x 19 2x8 9
3 3 - Char 40 x 19 2x8 16 ***
4 12 ++ Char 40 x 24 4x8 5
5 13 ++ Char 40 x 12 4x8 5
6 1 Char 20 x 24 8x8 5
7 2 Char 20 x 12 8x8 5
8 3 Map 40 x 24 4
9 4 Map 80 x 48 2
A 5 Map 80 x 48 4
B 6 Map 160 x 96 2
C 14 ++ Map 160 x 192 2
D 7 Map 160 x 96 4
E 15 ++ Map 160 x 192 4
F 8 Map 320 x 192 3 *
F 1 9 Map 80 x 192 16 or 8 **
F 2 10 Map 80 x 192 9
F 3 11 Map 80 x 192 16 ***
+ GTIA Modes require GTIA chip or FGTIA chip
(With CTIA these modes are considered valid by the OS but do not work.)
++ Supported by the XL OS (not supported by the 400/800 OS)
* 2 of the 3 available color registers share the same color/hue in this mode
* Modes capable of color artifacting on the NTSC Atari
** GTIA: 16 luminances of one color/hue
FGTIA: 8 luminances of one color/hue
*** 16 colors/hues all sharing the same luminance

GRAPHICS INDIRECTION (COLOR REGISTERS AND CHARACTER SETS):
Nine Color Registers are provided:
- Background (used in all graphics modes)
- Playfield 0-3 (at least one used in all graphics modes except GTIA 1&3)
- Player-Missile 0-3 (used in GTIA Mode 2; Player-Missiles discussed below)

Each color register holds both a color/hue setting and a luminance/brightness setting. In most graphics modes, each of the available color registers may hold any one of 16 colors/hues combined with any one of 8 luminance/brightness settings, for a total palette of 128 possible colors.

In GTIA Mode 1 only, with the GTIA chip only, the 16 available colors/hues can each be combined with 16 different luminance/brightness settings, for a total palette of 256 possible colors.

Character sets of 128 8x8 characters, each with a normal and an inverse
video incarnation, are totally redefinable.

PLAYER-MISSILE GRAPHICS:
The Atari term for "sprites" where a sprite is a graphical video display
object handled independently from the memory bitmap of the video display.

Four 8-bit wide, 120 or 240 byte high single color Players, and four
2-bit wide, 120 or 240 byte high single color Missiles are available.
A mode to combine the 4 Missiles into a 5th 8-bit wide Player is also
available, as is a mode to OR colors or blacken out colors when Players
overlap (good for making three colors out of two Players!) Players
and Missiles have adjustable priority and collision detection.

DISPLAY LIST:
Screen modes can be mixed (by lines) down the screen using the Display
List - a program which is executed by the ANTIC graphics chip every
screen refresh.

DISPLAY LIST INTERRUPTS (DLIs):
Other screen attributes (color, player/missile horizontal position,
screen width, player/missile/playfield priority, etc.) can be adjusted
at any point down the screen via DLIs.

SCROLLING:
Fine scrolling (both vertical and horizontal) can be enabled on any
line on the screen.

SOUND:
Up to 5 distinct sounds can be produced simultaneously: four main voices
plus the Console Speaker.

Sound output is monaural/monophonic/single channel, except for the
400/800 where Console Speaker sounds are output separately to a speaker
inside the computer.

The four main voices can be configured in one of the following three ways:
- 4 voices, each with one of 256 unique frequencies/pitches
- 2 voices, each with one of 65,536 unique frequencies/pitches
- 1 voice with one of 65,536 frequencies/pitches and 2 voices with one of
256 frequencies/pitches each

Each of the main voices may produce 8 types of tones: pure tones (square
wave type), or tones produced with one of 7 types of "noise" which is
known as "distortion" on the Atari.

Each of the main voices may be produced at one of 16 volumes.

Direct control of the position of the speaker cone, known today as pulse-
code modulation or PCM, is available at a bit depth of 4 bits, for a
volume resolution of 16 possible values (4-bit PCM). This is known as
"Volume Control Only" or "Volume Only" sound on the Atari.

The Console Speaker was intended only for system keyclick and buzzer, but
it may also be programmed as 1-bit PCM.

VERTICAL BLANK INTERRUPTS (VBIs):
A software routine may be designed to execute as a VBI. There are two
varieties of VBI: Immediate and Deferred. An Immediate VBI completes
execution within the vertical blank time, which is the time allotted for a
CRT display to shut the electron beam off at the lower-right of the
display and reposition it back on the top-left of the display to commence
drawing of the next frame. A Deferred VBI routine completes execution
between the initiation of one vertical blank and the next.

Atari 8-bit computers were supplied with the proprietary Atari Operating
System contained in Read Only Memory (ROM) as an integral feature of the computer. The Atari OS is described elsewhere in this FAQ List.

------------------------------

Subject: 1.2) What is the Atari 400?

Introduced at a New York news conference on December 14, 1978 alongside the Atari 800 and shipped the following fall, the Atari 400 was the reduced
feature set version of the new Atari personal computer system.

The 400 is the only 8-bit Atari with a membrane keyboard rather than a full- stroke keyboard, and is one of the few 8-bit Atari computers lacking a composite monitor port. Controller Jacks #1-3 on the 400 are the only ones on any 8-bit Atari that do not support a light pen / light gun. The 400 was originally released with just 8KiB RAM, but most were sold with 16KiB RAM. As of June 1983 Atari released the 48K RAM Expansion Kit for the 400, installed through Atari service centers or offered as a kit through the Atari Program Exchange (APX).

Any internal plug-in RAM board for the 400 can also be used in the front RAM slot of the 800.

Features unique to the 400/800 models relative to other Atari computers:
- Television (TV) connecting cable, not designed to be removable, emerges
directly from center of rear of computer case
- Four controller (joystick) ports
- Internal speaker for keyclicks and system buzzer
- Memo Pad / Blackboard mode
- 12 volt supply on pin 12 of the SIO port
- Internal plug-in 400/800 CPU Board (28/56 pin edge connector)

System initialization types supported:
- Memo Pad: Turn on computer with no cartridge inserted and no powered disk
drive #1.
- Cartridge: Turn on computer with cartridge inserted.
- Cassette boot: (boot cassette may or may not require cartridge inserted)
1. Hold down [START] while turning on the computer. (system buzzer sounds)
2. Press [PLAY] on the program recorder with boot cassette inserted.
3. Press [RETURN] on the computer.
- Disk boot: (boot disk may or may not require cartridge inserted)
Turn on computer with boot disk inserted in powered disk drive #1.

Versions of the Atari 400:
o Domestic version ("DOM") for NTSC M television (North America)
- 1979-1981 systems shipped with:
- 8KiB of RAM
- Atari BASIC Programming Language cartridge CXL4002
- Atari BASIC (Wiley Self-Teaching Guide) book C014385
- Atari 400 Operator's Manual C014768
- 1981-1983 systems shipped with:
- 16KiB of RAM
- The Basic Computer Owner's Guide C017711
- Microprocessor
- Most units: 6502 (MOS Technology MCS6502A or equivalent), C014377
- Late units: 6502 (Atari SALLY), C014806
- ANTIC NTSC version, C012296
- Early units: CTIA, C012295
Most units: GTIA NTSC version, C014805
- 10KiB Operating System ROM
- 400/800 OS, C012399 Floating Point Package (FPP) + C012499 + C014599
- Early units: 400/800 OS Rev.A/NTSC
- Most units: 400/800 OS Rev.B/NTSC
- No Monitor port
- Built-in TV connecting cable for TV antenna input
- Switch (unlabeled) on back of computer selects TV output RF channel:
2 or 3
- TV Switch Box supplied with computer
o "PAL"/"UK" versions for PAL B/G television (Western Europe) or PAL I
television (United Kingdom), respectively
- Shipped 1981-1983
- 16KiB RAM
- 6502 Microprocessor (Atari SALLY), C014806
- ANTIC PAL 'A' version, C014887
- GTIA PAL version, C014889
- 10KiB Operating System ROM
- 400/800 OS Rev.A/PAL, C012399 (FPP) + C015199 + C015299
- No Monitor port
- Built-in TV connecting cable for TV antenna input
- Switch (unlabeled) on back of computer selects TV output RF channel:
- Some units: 36 (PAL/UK) or 4 (PAL)
- Some units (Germany): 3 or 4
- Some units: Channel is fixed to either 36 or 4
- Manual: The Atari 400 Computer Owner's Guide C060200
- Peritel version (France) is the same as the "PAL" version (for PAL B/G
television) but has a second built-in TV connecting cable for RGB TV
input.
- Visual tour:
http://www.atari800xl.eu/hardware/computers/peritel-atari-400.html
- Other links:
- http://www.atariage.com/forums/index.php?showtopic=62346&st=25
- http://preview.tinyurl.com/ngsxhd8
- Rare! See L'Atarien #7 p33 for further reference.
- Speculation: Few units exist, hand-made by Atari France based on the
Peritel Atari 800

Technical manuals:
- Atari 400/800 Personal Computer System Service Manual
- August 1980
- May 1981
- Atari 400/800 Home Computer Field Service Manual FD100001
- June 1982
- Rev. 02 May 1983
- Atari 400/800 PAL-UK field service manual FD100002

Power: Used with an external 9 volt AC transformer power supply rated for at least 19 watts: Atari CA014748 or equivalent (including the Atari CA017964).

Atari marketing used the trademark, The Basic Computer, as an alternative name for the 400 from 1981-1982.

The 400 was manufactured at Atari's plant at 1173 Borregas Ave., Sunnyvale CA

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