the hard drive icon that appears on the screen when an HD-20 is running is actually stored in the HD-20's ROM
How has this been verified? Is there a dissected HD-20 ROM dump somewhere? Or is it referenced in some Apple literature?
I can tell you I've been disassembling the HD-20 driver in the Plus ROM and there are 256 bytes dedicated in the HD-20's status reply message for storing an icon. There is also a status bit that tells the Mac whether the HD-20 actually has an icon in that location. The HD-20 driver, when asked for an icon by the operating system (or whoever else), will happily return the icon sent from the HD-20 if it exists, or otherwise an error code.
Does anyone know if it has support for folders? Could I label different folders ( games, apps, ect) and select them From the EMU or does it only support images located in the root directory of the SD card.
Yep, bigmessowires added support for folders in one of the later updates. Works great!