Atari 800
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| Atari 800 home computer | |
| Specifications | |
|---|---|
| Manufacturer | Atari, Inc. |
| Type | Home computer |
| Released | November 1979 (first shipments)[1] |
| Discontinued | 1983 (production ended May 1983)[1] |
| Intro price | US$999.99 (1979 package with 8 KB and 410 recorder)[1] |
| CPU | 6502B (SALLY on late CPU boards), 1.79 MHz NTSC / 1.77 MHz PAL[1] |
| Memory | 8 KB or 16 KB RAM as shipped, later 48 KB, on plug-in modules in three slots; 10 KB operating system ROM on a plug-in module |
| Storage | Cassette or 5.25" floppy disk drive over SIO; two ROM cartridge slots |
| Display | 40 × 24 text, up to 320 × 192 pixels; RF and monitor outputs |
| Sound | POKEY: four audio channels |
| OS / Firmware | Atari Operating System on the ROM personality module; Atari BASIC on cartridge |
| Successor | Atari 800XL |
| Codename | Colleen |
| Model no. | 800 |
The Atari 800 is an 8-bit home computer made by Atari, Inc. from 1979 alongside the Atari 400. The two share a processor, custom chipset and operating system. The 800 is the larger model: it has a full-travel keyboard, a monitor jack, a second cartridge slot, and slots under a lid for its operating system ROM and its RAM modules.[2][1]
Atari's field service manual of June 1982 documents the 400 and the 800 together.[2]
History
[edit | edit source]The "Colleen" project produced two machines: the full "Colleen", released as the Atari 800, and the reduced "Candy", released as the 400. The first consumer units shipped in November 1979, 400s to Sears first and 800s shortly after. The launch package, with the 800 and an 8 KB RAM module, a 410 program recorder, the Educational System Master and BASIC cartridges and manuals, listed at US$999.99.[1]
In summer 1980 the package changed to 16 KB, without the recorder, at US$1,080. Atari cut the price to US$899 at the end of 1981 and made 48 KB standard in autumn 1982 at US$679, then US$499 without BASIC from January 1983.[1] When Antic published its first issue in April 1982, an 800 with 16 KB and an 810 disk drive cost US$1,679.95.[3] Production of the 400 and 800 ended in May 1983, and both were announced as discontinued when the 600XL and 800XL were shown at the Summer CES in June 1983.[1]
Early 800s have the CTIA video chip; the GTIA became standard in November 1981, together with operating system Revision B. Late machines have a revised CPU board with Atari's SALLY version of the 6502. The 800 was made in the USA.[1]
Architecture
[edit | edit source]The 800 is modular. Atari lists seven functional modules: the motherboard, the CPU board, the ROM personality board (800 only), one or more RAM boards, the keyboard, the power supply board and the program cartridge. The boards plug into the motherboard and share its address bus, data bus and clock lines.[2]
The motherboard generates the 3.58 MHz master clock for the CPU board and the power-on reset, drives the keyboard-click speaker, converts the hand-controller signals, buffers the data bus, does the first stage of memory-map decoding into 8 KB blocks, and builds the composite video and the television sound subcarrier.[2]
| Location | Atari P/N | Device | Function |
|---|---|---|---|
| A303 (CPU board) | C014377 | 6502B | Microprocessor |
| A302 (CPU board) | C012296 | ANTIC | Display list processing, bus control and DRAM refresh |
| A301 (CPU board) | C014805 | GTIA (CTIA on early machines) | Colour and luminance, player/missile graphics, collision detection |
| A101 (motherboard) | C012294 | POKEY | Keyboard scanning, serial I/O, four audio channels |
| A102 (motherboard) | C014795 or C014812 | 6520 PIA | Two 8-bit ports for the four controller jacks |
| A103 (motherboard) | C010816 | CD4050 | Hex buffer |
| Z101 (motherboard) | C014361 | 74LS42 | One-of-ten decoder |
| Z103, Z104 (motherboard) | C014336 | 4051B | Keyboard key-in and key-out multiplexers |
| Z105, Z106 (motherboard) | C014347 | 74LS243 | Data bus transceivers |
| A401, A403 (ROM module) | C014599, C012499 | 4 KB ROMs | Operating system: I/O, interrupts, initialisation |
| A402 (ROM module) | C012399 | 2 KB ROM | Floating-point package |
Part numbers and locations are from Atari's 800 parts list; functions are from the theory-of-operation section.[2] The CPU board is the same assembly (CA017173) as the 400's.[2]
On the 800 motherboard the CPU board plugs into J101 (28/56-way edge connector), the three RAM slots are J102, J103 and J104 and the ROM personality module is J107 (all 22/44-way). The cartridge slots are J108 and J109, the four controller jacks J110–J113 and the keyboard header J106.[2]
Memory and storage
[edit | edit source]Atari's manual describes the 800 with 8 KB to 16 KB of RAM as standard and two further sockets for RAM modules, to a maximum of 48 KB.[2] The first slot holds the CX801 10 KB ROM module (CX801.P on PAL machines); the other three take CX852 8 KB or CX853 16 KB RAM modules.[1] Atari rated the machine at 48 KB because that seemed enough at the time, leaving the top 16 KB of the address space for the operating system and the I/O block.[4] Early 800s have plastic cases on the ROM and RAM modules; later 48 KB machines have bare cards held by a plastic strip.[1]
The ROM personality module occupies $D800–$FFFF. Its two 4 KB ROMs hold the I/O subsystem, interrupt handling and power-up and reset initialisation; the 2 KB ROM holds the floating-point package used by BASIC and other programs.[2] The 400/800 operating system has no built-in self-test. Atari's service tests use the SALT II diagnostic cartridge.[2]
The left cartridge overlays $A000–$BFFF and the right $8000–$9FFF.[2] The right slot was meant for 16 KB programs; once 16 KB fitted in a single cartridge it went unused, and the 1200XL and later machines have one slot.[4]
Mass storage is external, on the SIO bus: the power supply board's peripheral jack J204 is daisy-chained to program recorders, disk drives and other devices, each with its own address.[2]
Display and sound
[edit | edit source]ANTIC with the CTIA or GTIA gives text up to 40 columns by 24 rows, bitmap modes up to 320 × 192 pixels, four players and four missiles with collision detection, and programmable display lists. The motherboard sends composite video, luminance, chroma and the modulator signal to the power supply board. There the RF module A203 produces the television signal on channel 2 or 3, and the monitor jack J205 carries composite chroma, luminance and video and audio out.[2]
POKEY provides four semi-independent audio channels, each with its own frequency, noise and volume control. The motherboard mixes its output with the cassette audio track.[2]
Input and output
[edit | edit source]The right side panel has the monitor jack, the peripheral (SIO) jack, the channel 2/3 switch, the power switch and the power jack. The four controller jacks are on the front. The two cartridge slots are under the top door, and an interlock switch cuts power when it is opened.[2] The 400 and 800 are the only Atari 8-bit machines with four controller ports, a keyclick speaker and +12 V on pin 12 of the SIO port.[1]
The keyboard has 57 normally-open switches, scanned and encoded by POKEY.[2] The four console keys to its right, SYSTEM RESET, OPTION, SELECT and START, are switches S204–S207 on the power supply board, wired to the motherboard through J202.[2]
Power
[edit | edit source]The external adaptor (Atari C014319) is a transformer that supplies 9 V AC to the power jack J206. The power supply board rectifies it and produces the console's rails:[2]
| Rail | J201 pin | Use | Source |
|---|---|---|---|
| +5 V A | 18, 19 | Logic boards | A202, 7805 (C014348), with R203 (33 Ω 2 W) across it |
| +5 V B | 17 | Video circuitry, specially filtered | +5 V A through L201, with C209 and C210 |
| +12 V | 21 | Dynamic RAM; also SIO pin 12 | Doubler CR204/CR205 with C204/C205, then A201, printed 78M12 (C014349) |
| −5 V | 1 | Dynamic RAM | CR202/CR203 with C201/C202, zener CR201 |
The power switch S202 and the interlock S201 both open the 9 V AC input, so a machine with the top door open appears dead.[2]
 | The regulated 5 V DC supplies made for the XL and XE machines do not fit the 800. The 800 needs 9 V AC at the power jack; its rectifier, regulators and filter capacitors are on the power supply board inside the console.[2] |
Checking a machine
[edit | edit source]Atari's power-up check needs no test equipment. With no cartridge fitted, switch on: "ATARI COMPUTER - MEMO PAD" should appear. A snowy, black or grey, green or yellow, or solid blue screen each has its own flowchart in section 7 of the manual. The deeper tests, including the RAM, ROM, colour bar and keyboard tests, use the SALT II cartridge in the left slot.[2] See the Atari 800 Troubleshooting Guide.
Antic gives PEEK(65527) = 221 for 400/800 OS Revision A and 255 for Revision B.[4] The FAQ gives PEEK(65528) instead: 221 for Revision A NTSC, 214 for Revision A PAL and 243 for Revision B NTSC.[1]
Schematics and service manual
[edit | edit source]| Schematics | Field service manual |
|---|---|
| File:Atari 400 800 Home Computer Schematics.pdf | File:Atari 400 800 Field Service Manual June 82.pdf |
The manual also has its own page: Atari 400 800 Field Service Manual June 82.
Related pages
[edit | edit source]- Atari 800 General Maintenance
- Atari 800 Troubleshooting Guide
- Atari 800 Capacitor Replacement Guide
- Atari 400
- Atari 800XL
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 Michael D. Current (ed.), Atari 8-Bit Computers: Frequently Asked Questions, comp.sys.atari.8bit FAQ, last modified 29 November 2009, section 1.3 "What is the Atari 800?" and the history timeline for 1978–1983. faqs.org. Community reference, used for dates, prices, codenames, model variants and clock rates.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 Atari, Inc., ATARI Home Computer Field Service Manual 400/800, June 1982. Section 1 (theory of operation, pp. 1-2 to 1-17), Section 2 (800 power supply schematic, Figure 2-8, p. 2-13), Section 3 (testing with and without the SALT II cartridge), Section 7 (800 diagnostic flowcharts) and Section 9 (800 parts list, pp. 9-7 to 9-13). Hosted here as Atari 400 800 Field Service Manual June 82 (PDF).
- ↑ Nat Friedland, "Editorial: Ever-Changing Atari Marketplace", Antic Vol. 7 No. 1 (May 1988), atarimagazines.com.
- ↑ 4.0 4.1 4.2 Robert DeWitt, "Inside Atari: Evolution of the XL Computers", Antic Vol. 3 No. 2 (June 1984), atarimagazines.com. Source for the 48 KB rating, the right-hand cartridge slot, the loss of joystick ports 3 and 4 on the XL machines and the PEEK(65527) values.