Super Magic Drive file format information
 by Charles MacDonald
 WWW: http://cgfm2.emuviews.com

 Introduction
 ------------

 I've verified all of this information on a real SMD, though I'll say
 the usual and warn that using any of this is at your own risk. :)

 1.) 68000 program files
 -----------------------

 Files generated by the copier are either single files as large as the
 floppy disk being used (720K to 1.6MB supported), or split files in
 units of 512k.

 Most SMD utilities will merge split files into single files larger
 than a single disk. These can still be used by the SMD by splitting
 them again or sending them through the parallel port.

 The files consist of a 512-byte header, and then several 16k blocks of
 interlaved 68000 program data. Each block is comprised of an 8K section
 of all the even bytes, and then an 8K section of all the odd bytes.

 Here is some "C" pseudocode for a function to convert a single block
 to a raw binary format.

    void smd2bin(char *inblk, char *outblk)
    {
        for(int n = 0; n < 0x2000; n += 1) {
            outblk[(n * 2 + 0)] = inblk[(0x0000 + n)];
            outblk[(n * 2 + 1)] = inblk[(0x2000 + n)];
        }
    }

 The SMD does not assign an extension to single format files, though
 by tradition people give the '.SMD' extension. Split files range
 from '.1' to '.8'. The last file in a split set has byte 02h of the header
 set to 00h, while other files have the same byte set to 40h.

 Header format:

 Byte 00h : Size of file in 16K blocks.
 Byte 01h : 03h
 Byte 02h : Split file indicator (00h=single or last file, 40h=split file)
 Byte 08h : AAh
 Byte 09h : BBh
 Byte 0Ah : 06h

 The remainder of the header should be set to zero.

 2.) Z80 program files
 ---------------------

 The SMD can accept Z80 programs, which are executed by the machine
 in the Mark-III compatability mode. For some reason, these files only
 work when loaded via floppy, as opposed to the parallel port. This
 could be a limitation of the SMD's firmware or an issue with the
 transfer utility, which may only expect to send 68000 programs.

 The files consist of a 512-byte header, and then the raw Z80 program data.

 Header format:

 Byte 00h : Size of file in 16K blocks.
 Byte 01h : 02h

 The remainder of the header should be set to zero.

 3.) Save RAM files
 ------------------

 Cartridge games can store data in battery-backed RAM or EEPROM.  Battery
 backed RAM is 8-bits wide, and can be wired to even or odd addresses.

 The SMD handles this by having a 32k SRAM chip wired to both addresses,
 which gives 16k of usable memory. The SMD does not support EEPROM for
 storing data.

 The files consist of a 512-byte header, and then a 32k image of the
 raw battery-backed RAM data.

 Header format:

 Byte 00h : 00h
 Byte 01h : 00h
 Byte 08h : AAh
 Byte 09h : BBh
 Byte 0Ah : 07h

 The remainder of the header should be set to zero.

 3.) Acknowledgments
 -------------------

 Thanks go to Bart Trzynadlowski for information on the SMD format.