DEC Rainbow disks - help

[Allison]

>
>Subject: Re: DEC Rainbow disks - help
>   From: Paul Koning <pkoning at equallogic.com>
>   Date: Thu, 28 Jul 2005 15:24:29 -0400
>     To: cctalk at classiccmp.org
>
>>>>>> "Tony" == Tony Duell <ard at p850ug1.demon.co.uk> writes:
>
> >> I just acquired a Rainbow with ~10 boxes of disks.  Most are for
> >> DOS it seems, though some for cpm/86.  Could someone explain the
> >> differences between the types of media meant to run on this puter,
> >> whether it has to do with os, or physical properties (soft
> >> sectored, hard sectored, RX50...). I also have access
>
> Tony> The RX50 drive (used in the Rainbow, and for that matter the
> Tony> Pro) is a 80 cylinder single-sided drive. The Rainbow (and Pro)
> Tony> have soft-sectored double-density controllers, and store about
> Tony> 360K on each disk.
>
> Tony> These parameters are independant of the OS used.
>
>That makes it fairly tricky to read, because 10 sectors per track is
>not a normal PC floppy mode.  It can be done in DOS (int13 level I/O)

I'd add tht at the time of the Rainbow and pro 80track drives were not 
common to PCs yet.

>and in Linux (by telling the driver to use nonstandard format
>parameters).  I have all that in the "rstsflx" utility for
>reading/writing RSTS file systems; I can post selected bits if that's
>of interest.
>
>The other confusing point is the addressing: logical block 0 is at the
>start of track 1, the sectors are 2:1 interleaved, and physical track
>0 holds the LAST 10 logical sectors...

????  CP/M disks nominally start logical block 0 after system tracks.
Dos disk are different and I never paid much attention to them.
POS for the PRO was same media but file allocation was different again 
from CP/M or DOS [or RT11 and VMS as well] on RX50.

Allison