Fedora Core 2 wishlists
Sam Varshavchik
mrsam at courier-mta.com
Thu Dec 18 03:46:52 UTC 2003
Giacomo Magnini writes:
> Sam Varshavchik ha scritto:
>
>> My old Atari ST computer used FAT on floppies. I think Amiga did to.
>> No. Amiga used a very funny filesystem for their floppies.
>
> Maybe AFFS is funny by today's standards, but at the time it was much
> more advanced than fat:
> - long filenames
> - more data on a floppy (880K instead of 720K)
That had nothing to do with the filesystem format per se. The additional
room was obtaining by completely eliminating inter-sector gaps.
FAT-formatted floppies have gaps placed in-between sectors on a track, in
order to take into account the setup time needed to place the R/W head into
write mode, and to take into account variations in recording speeds between
different drives.
Amiga floppies didn't have inter-sector gaps, which is where the additional
storage came from. Amiga floppies were read and written a whole track at a
time.
> - much faster (even for todays standard: ever tried formatting a floppy
> under Win?)
You've got to be kidding. Do you even recall the experience of trying to
open a folder from a floppy, in Workbench? Amiga's filesystem used hashed
directories. Reading a directory meant, essentially, traversing hash chains
all over the floppy. One block per file. Meaning that each directory entry
usually required a floppy head seek.
Each file block itself had a header. I think that each 512-byte block had
only 488 bytes of file data, the rest was the header. I forgot the exact
byte count, I think it was 488. That didn't really matter much with
floppies, but that meant that you couldn't exactly use DMA to read/write
data to/from a hard drive. An intermediate buffer had to be used for
processing the header and reading/writing it from the hear drive.
A “Fast File System” was added to a later revision of AmigaOS, which
basically removed headers from data blocks, allowing for much faster DMA
to/from hard drives.
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