Boot up without Harddisk or Floppy drive
The replay2 can boot on whats know as an sdcard, similar to whats in a camera or videocamera.
It uses a fullsize sdcard slot. cards might come in common sizes, 4/8/16/32gig etc. (SD or SDHC).
The sdcard will need to be formatted fat32 file system and will also need to be formatted with an operating system to boot up with.
Eg: For an Amiga boot, it will need to be partitioned using ffs/pfs3 file system. You will also need a workbench to be installed on top of this.
Partitioning can be done in winuae or on the Amiga directly. See the more information link below.
Also note, for an operating system to boot eg; Amiga (Workbench) or AtariSt (Tos), it will need a core loaded initially which is what the replay/replay2 looks for when you switch it on. These might commonly known as a .bin file. The replay looks for these files and if found will automatically load this after power on. eg: if you want to use the Amiga core, you will need at least the Amiga core files for example (noting you are also providing initially your own workbench and kickstart), and write them onto your fat32 formatted sdcard. (Always look for the latest core.)
Also note: you will need to edit the replay.ini etc on the sdcard for relevant configuration etc and whether the sdcard will then go onto boot to in Amiga’s case, to a kickstart only or and workbench as well. See this link for more information on how to do this. note: this will be the same Principal for most cores and games etc.