The goal of this project (by Jorgen Bilander) is to make a cheap and easy to build SD-Card adapter that connects to the parallel port of any Commodore Amiga. Special driver software provided by Niklas Ekström will then allow AmigaOS to mount the SD-Card as a file system. This Amiga hack uses an Arduino Nano V3 and a common cheap MicroSd Card Adapter that has a voltage level shifter on board. The throughput of the adapter is limited by how fast the 68k CPU can access the CIA chips. The CPU can make one access (a read or a write) to a CIA chip per E-cycle. The protocol used by the SPI adapter can communicate one byte every two E-cycles which gives a theoretical upper limit of 350 kB/s.
new source: SD-BOX or SPI adapter tutorial / image source: Niklas Ekström / watch on Imgur