DEC Rainbow disks - help

[Allison]

>
>Subject: Re: DEC Rainbow disks - help
>   From: Paul Koning <pkoning at equallogic.com>
>   Date: Thu, 28 Jul 2005 17:42:48 -0400
>     To: cctalk at classiccmp.org
>
>>>>>> "Allison" == Allison  <ajp166 at bellatlantic.net> writes:
>
> >> 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...
>
> Allison> ????  CP/M disks nominally start logical block 0 after
> Allison> system tracks.  Dos disk are different and I never paid much
> Allison> attention to them.  POS for the PRO was same media but file
> Allison> allocation was different again from CP/M or DOS [or RT11 and
> Allison> VMS as well] on RX50.
>
>I'm not talking about the file system, I'm talking about block
>numbering -- the linear block numbers (0 to 799) which sit underneath
>the file systems.  All the DEC PDP11 and VAX OSs use linear block
>addressing; the sector/track/cylinder structure of the drives exists
>below the file system only, and is mapped to LBA by the disk device
>driver.
>
>For example, on all disks, LBA 0 is the boot block.
>
>Ok, so where physically is LBA 0?  On most disks it is cyl 0 track 0
>sec 0.  But not on the RX50; there it is cyl 1 track 0 sec 0.
>
>So what LBA lives on cyl 0 track 0 sec 0?  Answer: I'm getting too
>confused in the arithmetic, but it's an LBA in the range 790 to 799. 

snipped...

OK, that applies to NON CP/M and DOS disks and I can see how it would be
a PITA to create DOS or CP/M media from other DEC systems.  Having done 
it in the past those memory bits were lost. ;)  Mostly due to trying to 
do the reverse (DEC OSs from CP/M hardware).

I see no other impact to the Rainbow from the RX50.

Allison