Apple II EEPROM + DISK II 2-in-1 Card

What is it?

A drop-in replacement for Apple's long-unavailable DISK II interface card, using a modern SST29EE010 EEPROM instead of the obsolete 256-byte PROM.

The board keeps the original 2-drive Shugart pinout and 13-sector/16-sector firmware, so any Apple II, II+, or //e can boot and write 140 KB disks exactly as it did in 1978 — only now the firmware can be reflashed in seconds.

Why Was It Made?

Original DISK II PROMs (2316B/6332) have been out of production for decades. NOS parts are expensive, unreliable, and often already half-dead. By moving the 2 KB image into a single 5V EEPROM, this card restores the interface to "new" status, eliminates UV-erase headaches, and gives owners an upgrade path: simply re-flash the EEPROM to add speed-matching, half-tracking, or even 800 KB 3.5" support later.

What Makes It Special?

• 100% hardware-compatible: Same 20-pin IDC connectors, same boot ROM entry points, same timing — no software patch required
• Dual-drive ready: On-board termination and daisy-chain header let you run two original Disk II drives (or modern 5.25" replacements) without extra cards
• Future-proof: The 128 KB EEPROM is 98% free — add diagnostic tools, disk-copy utilities, or even a tiny OS in the unused space
• Reflashable in seconds: No UV eraser, no EPROM programmer — update firmware via standard EEPROM write cycle
• Modern reliability: SST29EE010 rated for millions of erase/write cycles vs. one-time-programmable original PROMs

Key Specifications

• Compatible systems: Apple II, Apple II+, Apple IIe
• EEPROM: SST29EE010 (128 KB, 5V, in-circuit reprogrammable)
• Firmware: 13-sector and 16-sector Disk II boot ROM
• Drive connectors: 2× 20-pin IDC (Shugart pinout)
• Drive support: Up to 2 drives (daisy-chain header included)
• Disk format: 140 KB 5.25" floppy (standard Apple II)
• Slot: Any Apple II peripheral slot
• Power: 5V from Apple II bus
• EEPROM free space: ~98% (126 KB available for custom firmware)

Upgrade Possibilities

The 128 KB EEPROM leaves enormous room for future firmware enhancements — all flashable without removing the card:

• Speed-matching firmware for modern drive replacements
• Half-tracking support for copy-protected disks
• 800 KB 3.5" drive support
• Built-in diagnostic and disk-copy utilities