Atari's belated 2600 successor wrapped a 6502 around a smart graphics chip called MARIA that could throw far more sprites at the screen with little CPU help — and it kept the old TIA chip inside for full Atari 2600 backward compatibility. Good hardware, undone by arriving years late into Nintendo's era.
The Four Natures
each piece emerges by one of four natures
The Idea
the three-beat story
The MARIA chip reads display lists and uses DMA to composite many movable objects per scanline largely on its own — so the modest 6502 ('Sally') is freed up. Lots of flicker-free sprites, a real step past the 2600.
The original TIA chip is retained, so the 7800 plays the entire Atari 2600 library natively and uses the TIA for most of its own sound. An instant back-catalogue baked into the hardware.
Designed in 1984 but shelved during Atari's turmoil and released in 1986, it landed well into the NES era with weak third-party support — capable silicon overtaken by the market.
The Teardown — Click a Block
the machine, laid out as a block diagram — the main processor on top, the rest of the silicon beneath, buses showing what talks to what. Click any block to read its spec. An accurate architecture diagram (a teardown illustration, not a schematic).
The Spec Sheet
the headline numbers — the spec edition
~1.79 MHz.
display-list DMA · many sprites.
also enables 2600 audio.
cartridge ROM.
full native library.
The Reckoning
the teardown, and the honesty about it
The Domain: Open It and Spec It
the teardown
- EXEREÚNESIS takes a real, made machine apart down to the chip and writes the honest spec — not a story-world but a technical anatomy.
- >One of a growing series of console teardowns; siblings link from the marquee.
Two-Layer Honest
datasheet vs lore
- Settled: the Sally 6502, the MARIA graphics chip, the retained TIA, and 2600 backward compatibility are documented.
- Flagged: MARIA's strength was sprites/objects; the system was comparatively weak on sound and arrived late — stated, so it's not overclaimed against the NES.
Render, Not Invent
sourced
- Summarized from the public technical record for the ATARI 7800; the manufacturer and its engineers are cited, not minted.
- No ROMs, BIOS, or copyrighted code are reproduced. Emergents are physical components; the block diagram is an illustration, not a schematic.
The Roster
every chip and part as an ACI .agent — each a birth certificate & a nature (6)
