Date   : Mon, 05 Apr 2010 15:28:15 +0200
From   : rick@... (Rick Murray)
Subject: ADFS & 512 byte sectors

On 05/04/2010 02:22, Mark Usher wrote:

> Does anyone know at what stage did ADFS start using 512byte sectors, if
> it ever did. I presume it was at one of the RISC OS stages, v3.xx
> onwards,

I don't think they ever did.


I am open to correction, but my brain says (for 3.5" floppies):

   ADFS S (160K)         - 256 byte sector
   ADFS M (320K)         - 256 byte sector
   ADFS L (640K)         - 256 byte sector
   AFS0   (640K?)        - 256 byte sector

   ADFS D (800K) old map - 1024 byte sector
   ADFS E (800K) new map - 1024 byte sector
   ADFS other (HD, F...) - 1024 byte sector

Essentially, the 6502 based machines use a 256 byte sector, the ARM 
based machines use a 1024 byte sector. It's MS-DOS that uses 512 byte 
sectors. Dunno about Unixy formats, but those aren't natively supported 
by RISC OS.


 > when Acorn started to integrate IDE interfaces in their machines.

This was with the introduction of the A4/A5000 when they moved from 
discrete logic and specific controllers (i.e. 6551 serial, logic 
parallel, 1770 FDC...) to a single ISA-ish combi-IO chip that did "all 
the usual".

This is also when the ARM range moved from SCSI and/or ST506 (both via 
expansion) to using IDE natively on-board.


Best wishes,

Rick.

-- 
Rick Murray, eeePC901 & ADSL WiFI'd into it, all ETLAs!
BBC B: DNFS, 2 x 5.25" floppies, EPROM prog, Acorn TTX
E01S FileStore, A3000/A5000/RiscPC/various PCs/blahblah...