jms@tardis.Tymnet.COM (Joe Smith) (06/02/91)
The referenced article appeared in alt.sys.sun; I'm sure that the question has come up repeatedly in the ibm.pc groups as well. Hence the crossposting. In article <1991May15.092512.17375@iesd.auc.dk> dorf@iesd.auc.dk (Thomas Dorf Nielsen) writes: >At my site we have some programs that make it possible to read and write >MSDOS disks with the drives in our SPARC-stations. > >I just wondered: Does anybody know of programs for the SPARC that can read >and write Amiga-formatted disks? (Bypassing the SPARC->MSDOS->Amiga route.) Unless Sun has used a very weird floppy-disk controller chip capable of reading extremely non-standard sector formats, the answer is "no way". The MS-DOS format for 3.5 inch floppies is 8 or 9 sectors per track, 512 bytes per sector, single or double sided, 80 tracks. A particular pattern of bytes is written in the gap between sectors, and each sector has a sync byte and header that can be recognized by the disk controller. The Amiga also uses 3.5 inch disks with 80 tracks double sided, but that is where the similarity ends. To a standard floppy disk controller chip, each track looks like a single sector of 5874 bytes with no inter-sector gaps, and the start of the track is not synchronized with the index pulse. The Amiga sectors do have individual headers, but in a proprietary format. Since there are no gaps between sectors, an operation that changes a single sector on the disk has to rewrite the entire track. The advantage is that the Amiga can store 880K bytes per floppy (instead of 720K bytes), and can read/write large blocks of data about 50% faster than the standard format. The format per sector is: 4 bytes for sync (00, 00, A1*, A1*), 4 bytes for header (format, track, sector, rotation), 16 bytes reserved for OS use, 4 bytes of header checksum, 4 bytes of data-area checksum, 512 bytes data. Additional details can be found on page 922 of the "Amiga ROM KERNEL Reference Manual: Libraries & Devices", in the Floppy Boot Process section. In summary: No other computer can read an AmigaDOS formatted floppy. To transfer data to/from the Amiga and other computers, use MS-DOS 720K format. -- Joe Smith (408)922-6220 | SMTP: jms@tardis.tymnet.com or jms@gemini.tymnet.com BT Tymnet Tech Services | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms PO Box 49019, MS-C51 | BIX: smithjoe | CA license plate: "POPJ P," (PDP-10) San Jose, CA 95161-9019 | humorous dislaimer: "My Amiga 3000 speaks for me."