ROM 4X and 5X

ROM 4X and 5X are enhanced firmwares for the Apple //c and Apple IIc Plus.

Main features:

  • Initializes memory expansion card without erasing it if it already contains a boot sector. This is intended for battery-backed memory expansions made by A2Heaven.
    • Allows dropping into the monitor immediately.
    • Allows clearing memory expansion card.
    • Allows launching diagnostics.
    • Allows selecting boot device.
      • 4X: Allows booting external 5.25 drive if disk supports it.
  • 5X: Replaces accelerator firmware.
    • CTRL+ESC+RESET toggles accelerator speed and persists across ordinary resets.
    • CTRL+TAB+RESET brings up a menu that lets you set accelerator state and some option.

In development:

  • 4X - available in pre-release: Configure ordinary boot to behave as if one of the menu options was selected.
  • 5X - in the works: additionally, set accelerator state (disable/speed/paddle delay/speaker delay).

See ROM 4X and 5X on GitHub.