The Atari 800 had 4 user accessible slots for adding RAM and a ROM card. Normally, your machine came with at least two cards from what I understand.

The question is, if I removed all the cards from the machine, would it power up at all? Could you run a cartridge without the ROM card perhaps? As well, would it work without any RAM cards installed? What would the machine do if nothing was in there?

I'm asking this question since I need to diagnose an 800 which recently stopped working and displays only a dark gray screen. Since one of the diagnostic steps is to remove the cards to see if they're at fault, I'm curious if I can remove them all to determine some state.

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    I had forgotten/never known about the funky module system in the 800 for the ROM and RAM. I found this but haven't read through it yet for your specific question: archive.org/details/Atari_400-800_Service_Manual
    – Joe
    Commented Oct 27, 2016 at 20:02
  • I'm guessing however you need at least the ROM module and one RAM module in there, given the 6502 boot sequence (which would hit the RESET vector and expect enough RAM for things like zero-page etc.) But that's supposition.
    – Joe
    Commented Oct 27, 2016 at 20:08
  • This document also looks promising: atarimania.com/documents/… especially starting on page 25 which describe boot sequences.
    – Joe
    Commented Oct 27, 2016 at 20:11

1 Answer 1


I just booted mine with the three 16KB RAM packs removed. At power up it displayed a green screen. With a Centipede cartridge, the 10K ROM pack, and no RAM packs, it just displayed two medium grey, inch-wide vertical lines on a black background.

I then removed Centipede and the ROM pack (RAM still removed). It still displayed a green screen. I then installed the RAM packs without the ROM pack and it still displayed a green screen.

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