The Replay board currently works a little differently to the minimig boot.
The board boots up an FPGA image which displays a boot menu, which lets you scroll through directories to chose a platform. (Actually, the boot platform is just the one it files in the \replay directory - it could be any core)
Each directory can contain a .ini file which sets up video standards, clocks and other core specific options (these also appear as on screen selections)
The ini file also gives a list of files to load into DRAM at specific addresses (think ROMs here).
Finally, the ini file also can select default image files to mount as floppy/hard disk images. The ini file can of course be easily edited by sticking the SD card in a PC.
This is all driven by the ARM controller. I am still developing this code, I'm not quite there at the moment, but close.
sorry a bit brief, on holiday at the moment so using the 'phone.
/MikeJ