Editing Apple IIc (section)

===UniDisk 3.5 support (ROM version '0')===
This update, introduced in November 1985, doubles the ROM firmware in size from 16&nbsp;KB to 32&nbsp;KB. The new ROM supports "intelligent" devices such as the [[Macintosh External Disk Drive|Apple UniDisk 3.5]]-inch (800&nbsp;KB) floppy drive and Smartport-based hardisks, in addition to an external 5.25-inch floppy drive. A new self-test diagnostic is provided for testing built-in [[Random-access memory|RAM]] and other signs of logic faults. The Mini-Assembler—absent since the days of the [[Apple II Plus]]—returned, and new Monitor "Step" and "Trace" commands. The upgraded ROM adds rudimentary support for an external AppleTalk networking device. When attempting to boot virtual slot 7, users see "APPLETALK OFFLINE", but no compliant device was ever released. The upgrade consists of a single chip swap and minor motherboard modification, which Apple provided free only to persons who purchased a UniDisk 3.5 drive. A small sticker with an icon of a 3.5-inch floppy diskette was placed next to the existing 5.25-inch diskette icon above the floppy drive port indicating the upgrade.