| Name | ATARI 7800 PRO System |
| Codenames | 'Maria' (the whole project and name of the graphics-chip), 'VCS 3600' (planned name in early development stage), 'CX-9000' (planned name later in development) |
| Made by | ATARI Corp.
Sunnyvale, California |
| Released | 1986 (although developed in 1983, see misc) |
| Serial-No. | X2 1 6 5 056939 |
| Additional Info | ATARI MODEL NO. 7800 PAL-B
FCC ID: EBA72R7800
ATARI CORPORATION
MADE IN CHINA |
| Board-info | - ATARI CORP.
C300633-001
REV C - © ATARI
CORPORATION
C300452 REV.C (on daughterboard) - 300633-001 REV C (board's lower side)
- this 7800-board seems to be PAL & NTSC-capable - there are certain unfitted part locations on the board, with 'NTSC' printed next to them (unfitted, since this machine's PAL)
- while Rev. A boards still had a side-expansion port, it was ommited
in Rev. B/C boards (making the 7800 keyboard useless, by the way)
- also see the board overview
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| CPU | UMC UM6502I 'SALLY'- also referred to as 6502C. It's an ATARI-customized 6502, which comes with only one additional feature: a HALT line. With that, the CPU can be completely halted, allowing other devices to fully access the system bus (required for MARIA's DMA-mode)
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| Speed | 7800-mode: 1.773447 MHz (PAL)/ 1.79 MHz (NTSC)
2600-mode: 1.182298 MHz (PAL)/ 1.193 MHz (NTSC)- generated by dividing the machine's 14.187576 Mhz (PAL)/ 14.28 Mhz (NTSC) crystal by 8 (7800-mode) or 12 (2600-mode)
- since TIA and RIOT can only be clocked at VCS 2600-speed, the 6502C has to be slowed down to 1.182298/ 1.193 MHz when accessing them in 7800-mode (where they are required for sound and I/O). In 2600-mode, the whole machine runs at that speed, and MARIA is disabled
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| RAM | - 4 KBytes:
- 2 pcs. STC 8828 (2Kx8 CMOS SRAM) on daughterboard
- can be used for storing data and code (e.g. MARIA's display list)
- can only be accessed in 7800-mode
- 128 Bytes (128x8 SRAM) integrated in UM6532
- called 'SARA'; the only RAM available in 2600-mode
- can only be used for storing data, not code
- unavailable in 7800-mode
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| ROM/ Native OS | C300558-01B '7800 PAL OS-ROM' (16Kx8)- the NTSC OS ROM contains an encryption check: when a cartridge is inserted, the 7800 searches for a valid encryption key in it. If that isn't found, it means either the game is a 2600-cart (so the 7800 stays in '2600 compatibility mode' with MARIA disabled), or it is a pirated game (which will not run in 2600-mode, of course). Clever! However, the PAL OS ROMs don't seem to contain such an
encryption check, because of the USA's export regulations on encryption
- like all european 7800s, this machine's OS ROM contains the game Asteroids, launched when no cartridge is present upon power-up. The NTSC machines came without it, and thus only had 4 KB ROM
- external ROM:
- cartridges with up to 144 KB capacity ('Atari Super Game Cartridge'), theoretically more
- bankswitching was needed for carts greater than 32 KBytes
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| Keyboard/ Layout | - none, but there was a keyboard-expansion that, in connection with a special cartridge, turned the ATARI 7800 into a fully-functional 8 bit-computer (which was neither compatible with the ATARI 400/ 800s nor with the XL/ XE-series, due to the very different hardware of the 7800). However, the keyboard is only usable with earliest 7800 revisions - later boards (like that of this particular machine) lack the required expansion port
- unit has SELECT-, PAUSE- and RESET-buttons (all three on its top), as well as a Channel 2/ 3 switch (on its back) and two more to set thr difficulty level for each port (front)
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| Graphics | C025718-30 'MARIA' @ 7.093788 MHz (PAL)/ 7.16 MHz (NTSC)
C398052-001 'TIA' (in VCS 2600 compatibility mode)- Max.Res.: 320x192 pixels in 2 colors
- theoretically, a maximum of 262 scanlines can be displayed. But for compatibility with the variety of TV sets and standards, ATARI recommended 192 scanlines (with the rest VBLANKed). Furthermore, MARIA features pre-defined display modes (the 2600's output depends on the 6507 CPU cycles) and bitmapped graphics
stored in two framebuffer-like circuits (the so-called 'Line-RAM', part of MARIA)
- in 2600-mode, display output is, of course, limited to TIA's graphic capabilities (see VCS 2600)
- Max. Colors: 16 at 160x192
- from a 256 colors palette (16 hues * 16 luminances)
- like ANTIC (used in 400/ 800/ XL/ XE), MARIA can combine two display-modes via display-lists (although MARIA's display lists work different from ANTIC's); that allows to display all 256 colors at once (mostly used for demos)
- also similar to ANTIC is that MARIA is DMA capable.
By halting the CPU it gains full access to RAM and ROM (i.e. to read the display-list or access the cartridge), and acts like a second CPU in the 7800-design. In the NTSC 7800, by the way, MARIA is also responsible for running the initial encryption check (see 'ROM')
- this is a PAL-B version of MARIA; NTSC-versions were C024674, C025349 and C025314. C025718 was the SECAM-variant
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| Sound | generated by TIA- TIA contains two independant audio-circuits. Each can be programmed
- in volume (16 levels possible)
- to output sound at a given frequency (1-30 KHz) or
- to output various noises (noise-tone generator)
However, although both circuits can be used simultaneously, they only output to one speaker (i.e. mono) - in PAL-machines, sounds are generated with a lower pitch, since TIA's clocked slower here (1.182298 MHz)
- because many complained about the TIA-sound in the otherwise advanced 7800,
some later games came with their own POKEY-soundchip (like Ballblazer), which was also used in 400/ 800/ XL/ XE. This was made possible by adding AUDIO- and CPU-lines to the cartridge slot
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| Media | cartridges via 32 pin slot on its top (see 'ROM')- can also handle the 24 pin VCS 2600-cartridges (which start the machine in 2600 mode, since they don't have a 7800 encryption key)
- very interesting is that in the 7800 design, the cartridge slot features additional audio-, address- and CPU-lines (such as HALT, CLOCK, READ/ WRITE and even composite video). Some carts made use of these by coming with their own POKEY-soundchip; theoretically, additional videochips or even CPUs are possible!
- an official 7800 Development Kit was available for the ST-series.
It came with a programmable development cartridge, which was connected to the ST via parallel cable. It also included 'game standards', which made clear how a 7800-game should look like. Compared to the 2600's game standards (coming with the 2600 DevKit), the 7800's were more technical (i.e. how to handle memory and encryption circuit), and they didn't contain info on NTSC/ PAL/ SECAM compatibility anymore. As a result, ATARI 7800 games running on the wrong console don't just behave strangely (like many 2600 games that depend on a certain timing) - they just crash...
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| Input/ Output | UMC UM6532 RIOT/ PIA (interval timer/ timer IRQ, two 8 bit I/O-ports)
TIA (to trigger the joystick-buttons with its I/O-ports)- in 7800-mode, RIOT is only used for joystick & switch I/O, its timers and RAM can only be used in 2600-mode. TIA's I/O-functions (i.e. fire buttons & paddle controllers) are utilized in both modes
- Machine connectors:
- 32 pin cartridge connector (on its top)
- 2x 9 pin controlpad/ lightpen/ lightgun
- RF-out (for TV)
- 2 pin power supply connector
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| Miscellaneous | - The ATARI 7800 PRO System was successor to the 5200 SuperSystem (1983); in comparison with the 5200, the 7800 is fully VCS 2600-compatible without additional hardware (i.e. there's a handful of 2600-carts, which won't work in later NTSC 7800 board revisions - probably ATARI had changed some parts for cost-reduction). The 7800 Development Kit calls it a 'product which combines the ATARI 2600 hardware with a new graphics chip called MARIA'
- The name also contains information on that: '7800' = the 5200's graphics capabilites + 2600-compatibility! It was additionally called PRO System because of the new CX24 'Pro Line' controllers (however, this machine, like most others sold in Europe, has the newer CX78 'Nintendo-style' controlpads)
- Although the machine's MARIA-chip was already designed in 1983 and the VCS 3600-prototype was functional, ATARI decided not to release it at first. Reasons were the crash of the videogame market ('videogame shakeout' in 1983), and that ATARI had been bought by Jack Tramiel (1984), who was more interested in producing his computer-system, the ATARI ST,
to rival his 'ex'-company, Commodore
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