The SDcard is used primarily to boot the replay. ie: When the Replay powers on etc, eventually it looks to the sdcard for software to load or boot up like a real computer. Basically, it has to be formatted fat32 and then usually whats known as a core is loaded into the system or memory of the replay if you like so as to run different operating systems or games etc. eg: Commodore64 or Amiga / AtariST or Amstrad etc. It also uses what is commonly called .ini files which is like a .bat or script file in which it not only loads the Core or and OS it tells the replay how and what to boot up after the initial power on, basically this .ini file loads the reset of the core and dependent files which might also be rom or audio / gfx etc, its like the control…Follow this link to see how to setup an example of an Amiga sdcard to boot for gaming or the workbench.
Note: If you don’t have an SDcard in the replay when you power it on, it will come up with a default replay picture telling you to insert an SDcard.