A604 RAM Expansion 1 MB for Amiga 600 (upgrades the A600 to 2 MB ChipMem) clock ports

[Colani1200]

however, superior communist technology designed by russian comrade NedoPC allows you to add a whopping 8MB of fastram (or 5.5MB keeping PCMCIA)!

But not for the trapdoor (can't be done).