jms@tardis.Tymnet.COM (Joe Smith) (10/04/89)
I created an 850K zoo file on a Unix system, copied it to my hard disk, and
then tried to copy it to a floppy. It didn't fit! I know you can't put an
880K file onto an 880K floppy, but I hadn't added up the overhead until now.
After subtracting the two reserved blocks (boot blocks), a freshly formatted
floppy has 1758 blocks before the file system overhead is taken into account.
That is not 879K, it is 1758*488=857904 data bytes (with 24 bytes of
AmigaDOS overhead per block). But the root directory takes one block, and
the file header takes another block, and additional file list blocks are
required to describe each set of 72 data blocks. The maximum size file
needs 25 of these; the file header plus 24 extensions.
2 reserved blocks (boot blocks)
1 root directory block
1 file header block (file name and pointers to first 72 data blocks)
24 file list blocks (each with pointers to up to 72 more data blocks)
1731 data blocks with 512-24=488 useable bytes per block
1 bitmap block (optional, 1732 data blocks means an unvalidated disk)
----
1780 blocks total on an 880K OFS floppy
If you punt off the bitmap and go for a 100% full floppy, then it is
1732*488 = 845216 bytes, but the disk-validator will run every time the
floppy is inserted.
1731*488 = 844728 bytes = largest single file on a standard Amiga floppy.
--
Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com
McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms
PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P,"
San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga did!"post@cpsc.ucalgary.ca (The Postman) (10/06/89)
Joe Smith writes: >I created an 850K zoo file on a Unix system, copied it to my hard disk, and >then tried to copy it to a floppy. It didn't fit! I know you can't put an >880K file onto an 880K floppy, but I hadn't added up the overhead until now. [stuff deleted about block calculation etc...] To get around this problem, you might try using a program called DosKwik. The two programs Readkwik, Ritekwik write directly to tracks in amigados format (ie you can diskcopy them) but don't have any file overhead (ie not a legal dos disk, sorta like kickstart) just the raw image. I have found that a disk holds over 900K this way. The program is found on a Fish Disk somewhere. Lenny Post Member/Exec of AMUC (The AMiga Users of Calgary) >-- >Joe Smith (408)922-6220 | SMTP: JMS@F74.TYMNET.COM or jms@tymix.tymnet.com >McDonnell Douglas FSCO | UUCP: ...!{ames,pyramid}!oliveb!tymix!tardis!jms >PO Box 49019, MS-D21 | PDP-10 support: My car's license plate is "POPJ P," >San Jose, CA 95161-9019 | narrator.device: "I didn't say that, my Amiga Did!