In 2012, Sebastian Bartkowicz (Candle) asked if I could write a
PBI version of the SpartaDOS X soft-driver I had written the
previous year for the SIDE cartridge. The reason was that he was
considering adding PBI emulation to his
Ultimate 1MB RAM upgrade, to
be used in conjunction with the SIDE cartridge, which would then be
present merely to provide the IDE interface itself. It seemed almost
an obvious thing to do in retrospect, but in any case Sebastian made
the necessary amendments to the Xilinx firmware and fed my hungry
appetite for switchable PBI ROM banks and RAM under the hardware
registers. I'd already written an experimental APT (Atari Partition
Table) BIOS for the KMK/JZ HDD interface, and was able to get
something rudimentary working for U1MB in a few weeks.In the ensuing months, Sebastian thought of more and more things to add (such as the ability to read and write disk images mounted in the FAT partition of the CF card), and after weeks of coding and debugging, we had something approaching a final version. Yet more features were added at the beginning of 2013, at which point three of the four PBI ROM banks were nearly full of code.