[iyonix-support] Re: 2nd harddrive problems

  • From: Kade Hansson <kade.hansson@xxxxxxxxxxxxxxxx>
  • To: iyonix-support@xxxxxxxxxxxxx
  • Date: Wed, 07 Mar 2007 16:51:15 +1100

Simon Smith wrote:

So, is there any chance of an update to DOSFS any time soon? Once DOSFS can
handle modern-sized discs, that would definitely help me justify paying for
an upgrade. There are a handful of other enhancements and bug fixes that
might also tilt the balance in favour of an upgrade, but a modernised DOSFS
would be a major factor. Other improvements I'm keeping an eye out for: bug
fixes to Edit so that it handles large files better; PNG support for
ChangeFSI; various other Adjust-like enhancements; a few other minor things
that don't currently come to mind. USB 2.0 and the other 5.12+ goodies
aren't really worth it for me, yet.
The limit in DOSFS is basically a FileSwitch limit (although, as is always the case in the tangled FS web woven in RISC OS, FileCore/ADFS is also involved.) A file pointer or address in FileSwitch is a signed 32-bit number. DOSFS works as an image file system, so it can only handle images as big as FileSwitch's file pointer can read. i.e. 2GB.

If someone wrote a FileCore-based FS which implemented Windows' filing system (FAT,) we could work around this limit. (ADFS is not constrained by the 2GB limit except in terms of file sizes.) However, for DOSFS itself to be upgraded:

- FileSwitch needs a >32-bit API (probably 64-bit) for file pointers (e.g. OS_Args, OS_GBPB etc.)
- FileSwitch needs a >32-bit (probably 64-bit) aware Image FS interface
- DOSFS needs to be rewritten to use both these new interfaces

That's quite a bit of work, right there. Until RISC OS Open, I had no hope personally.

Another issue is that from Windows 2000 (and that means XP and Vista as well,) HDs on Windows are actually NTFS, not FAT. So that's a whole new module anyway.



Simon Smith

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