Date   : Tue, 21 Apr 2009 00:25:32 +0100
From   : jgh@... (Jonathan Graham Harston)
Subject: ADFS on a CF card

"Mark Usher" wrote:
> Can any of the programs that can read a BBC ADFS CF card, also read one that
> is using a larger sector size. Ie. I have changed the IDE hard drive in a
 
I keep banging on about this and it never seems to get through.
 
BBC/Master ADFS using IDE devices uses native IDE 512-byte sectors,
only half those 512 bytes are used. More specifically, there are
256 16-bit words in each sector, and only 8 bits of each 16 bit
word are used. At the byte level, 8-bit ADFS uses each even
numbered byte and ignores each odd numbered byte.
 
It is in the ATA/IDE specification that sectors are 256 16-bit
words (ie, 512 bytes). There is no way to "reformat" an IDE device
with a different sector size.
 
> RISC PC 3.71 to a CF card. It is also formatted with ADFS, but I presume
> using the 512k sector size. Can any of these programs around cope with this?
 
Anything that can access an IDE device will access a Compact Flash
card regardless of what's on it. If you use a program that expects
to see an 8-bit ADFS 'L' format filesystem on it, it will not
understand te 32-bit ADFS 'F' format filesystem that RISC OS will
have put on it.
 
I have tried putting an 'L' format ADFS hard drive into a RISC OS
machine, but it isn't recognised. Elsewhere I've been told that
RISC OS is incapable of recognising 'L' format hard drives, only
floppies.
 
-- 
J.G.Harston - jgh@...                - mdfs.net/User/JGH
RISC OS Choices System - http://mdfs.net/Software/RISCOS