Atari 2600 Hardware Acceleration | Big Mess o' Wires

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2023-01-24 08:00:14

Atari 2600 programming techniques are fascinating. The hardware is so very limited, and programmers must use every possible trick to scrimp and save the last CPU cycle and byte of RAM. For a refresher on the 2600 hardware, check out my previous Atari overview. The console’s longevity is remarkable, with new games and demos still being produced today – over 100 new titles last year alone. The quest for the ultimate Atari 2600 programming techniques has continued all this time, in order to wring out maximum performance.

Atari programming requires racing the beam, updating graphics registers just before the instant they’ll be used to paint the next pixels on the current scan line. With only 76 CPU cycles per scan line, there just isn’t enough time for the poor 6502 to do very much. Want to update the foreground color multiple times at different horizontal positions? OK, but there might not be enough time remaining to also update the pixel bitmap during the scan line, or set the sprite positions. It’s a series of difficult tradeoffs and code optimization puzzles.

To create better-performing Atari games, programmers may need to think outside the box – literally. The 2600 console consists of a 6502 CPU (actually a 6507), a 6532 RIOT, and an Atari custom graphics chip called TIA. But what about the game cartridge? What’s inside that? The Atari’s designers envisioned cartridges as simple 4KB ROMs in a protective plastic shell, but there’s no reason aside from cost why there couldn’t be other hardware inside a cartridge too.

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