cfe...@freeremoveuk.com.invalid wrote:
> In message <76v*
Nq...@news.chiark.greenend.org.uk>
> Theo Markettos <
theom...@chiark.greenend.org.uk> wrote:
> > It's not a problem with 512 byte sectors (the USB floppy standard
> > includes options for different sizes), it's that the standard
> > provides no means to read sectors numbered below 1 (ADFS numbers from
> > 0, DOS numbers from 1).
> >
>
> Does this mean that it can't read from a particular part of the disc?
Yes... floppies have two sides, which are divided into tracks (eg 80
tracks), a track being a circle on the disc. Each track is divided into
sectors, a sector being a small arc of the circle. The number of sectors
varies depending on the data density and sector size - it's five 1024-byte
sectors numbered 0-4 for an E format disc. Due to the numbering issue, a
drive that can't read sector 0 can only read 1-4 and will miss out on every
fifth sector... in other words big chunks of data will be inaccessible.
> Have a program '!InitDisc' - that initializes (not formats) a DOS 1.4
> floppy into a RISC OS one of the same size.
>
> If the PC floppy drive can read the DOS disc - why can't RS read the RO
> version?
You can make an ADFS disc with a peculiar sector sizing and numbering that
happens to match DOS, and ADFS should cope with that. Back in the 90s there
were some 'special' ADFS formatter programs that did similar things to squeeze
out more space from a disc by pushing the drive hardware past the advertised
limits - like having 82 tracks and similar. Such a disc should be readable
on a USB drive.
But this is a 'special' format... might be handy for copying things from an
A5000 without other connectivity, but not for reading old floppies you
already have (which is what most people want to do).
> In lots of cases - it is just as easy to use DOS format disc - just put
> the file in a Zip.
Indeed.
Theo