The FocusDrive3 device driver supports the Focus IDE interface card in the Apple /// as part of the SOS operating system. SOS is very much like ProDOS in terms of filesystem layout; however, most Apple /// interpreters use a signed integer to represent blocks, so the standard maximum size of partition for ProDOS (65535 blocks, ~32MB) is halved in SOS as 32767 blocks (~16MB).

There's no ///-based partitioning software avaialble, so you will want to have a pre-partitioned CF card or IDE drive with partitions of size 32767 blocks (~16MB) or less for best results. As of this writing, the partitioning software only runs on the IIgs.

• Read
• Write
• Up to 8 partitions
• Integrated formatter

The driver is built via the ca65 assembler (part of the cc65 toolchain). Rob Justice's excellent a3driverutil enables rapid development by not requiring the developer to ever run SCP! It's a modern marvel.

Tools required:

• Ant
• ca65/ld65
• Python

Tools included as part of the build:

• a3driverutil
• AppleCommander