Frodo offers four possibilities for the 1541 emulation:
1. Host system directory, setting "Dir"In this mode, the C64 programs and files are stored in a directory on your hard disk and can be LOADed and SAVEd as usual from the emulator. The paths to the directories of the simulated drives are given in the settings window in the path entry fields of the "Drives" box.
You can also load the directory with LOAD"$",8. All files are displayed as "PRG", all subdirectories as "DIR". To get into a subdirectory, you have to open the settings window and change the path for the drive, as the operating system of the C64 doesn't know about subdirectories. However, it is possible to use a "/" in the C64 file name to access these subdirectories (e.g. LOAD"GAMES/ELITE",8), unless the '/' translation setting is turned on.
For the opening of files, the file types "P" and "S" and the access modes "R", "W" and "A" are supported. Wildcards (*,?) can be used, but you have to remember that files in BeOS/Unix/AmigaOS directories have no determined order and the result of LOAD"*",8 is rather random. Files are always overwritten even if they are not opened with "@:". Floppy commands other than "I" and "UJ", relative files and direct block access are not implemented. You can however read the error channel.
2. .d64/x64 disk image file, setting "D64"Most C64 programs available on the Internet and on CD-ROMs, expecially demos and games, are stored in files with the ending ".d64". Such a file holds all 683 blocks of a complete side of a 1541 disk, so that direct block accesses are possible from within the emulation. However, Frodo only supports read accesses. The path name of the disk image file must be given in the settings window in the path entry fields of the "Drives" box.
Apart from .d64 files, Frodo can also use image files of the "x64" emulator, automatically detecting the file type.
3. .t64/LYNX archive file, setting "T64".t64 and LYNX (.lnx) files are archive files like "tar". .t64 files are also often found on the Internet and on CD-ROMs; LYNX is a native C64 archiver. Frodo's .t64 support is a bit special in that it doesn't treat the .t64 file like a tape image (that's what the .t64 format was designed for), but rather like a disk image file. .t64's are not accessed with device number 1 (Frodo doesn't have any tape emulation), but with numbers 8..11 like a disk drive.
When loading the directory with LOAD"$",8, Frodo creates a listing of all files within the archive. You cannot write to .t64 or LYNX files, they are read-only under Frodo.
4. Processor-level 1541 emulationThe 1541 is an "intelligent" disk drive bearing its own CPU and memory that can even be programmed and execute code concurrently to the C64. Frodo is able to emulate a 1541 on this level, but as this slows down the whole emulation notably, the 1541 processor emulation can be turned on and off from the settings.
If the 1541 processor emulation is turned on, the "Dir"/"D64" drives 8..11 are no longer available. They are replaced by a single drive with number 8 that operates in "D64" mode (regardless of the state of the type setting for drive 8). The path name of the .d64/x64 file to be used must be given in the path entry field of drive 8.
In contrast to the standard "D64" mode, the 1541 processor emulation is able to write to the disk. There is no way to "virtually write-protect" the disk image file, so be careful.