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Apple IIc Plus Secret Disk II SmartPort

In the course of disassembling the Apple IIc Plus firmware, I discovered a secret ProDOS block device and SmartPort implementation for the Disk II.

The implementation is complete, including read/write/format, minus a few bogus values in the SmartPort device information.

The entry points are:

Address Implementation
$C64E ProDOS Block Device
$C651 SmartPort

It is possible to replace the ProDOS 8 device driver address for slot 6 ($BF1C for drive 1, $BF2C for drive 2) with the block device driver address $C64E, and ProDOS will then operate the Disk II using the firmware driver.

I wrote up the discovery here.