DEC RD53 hard - test-drb@ccmp.vtda.org

15 Jan 2014

On 2014-01-15 21:13, Al Kossow <aek at bitsavers.org> wrote:
...
  On 1/15/14 7:37 PM, Glen Slick wrote:
> >Does this apply to the RQDX3 disk format?
> >
> >Disk format for secondary storage system
> >US 4434487 A
> >https://www.google.com/patents/US4434487 
It sortof do. This is a description of how the disk logically appears in 
an MSCP subsystem. RQDX controllers are MSCP. I can't see that it holds 
enough low level detail to actually be used as a source to figure out 
how each block on an RD53 will look like. (But I have only read through 
it cursory.)

...
  Did the RQDX3 come out of Colorado Springs? 
I don't think so.

...
    From the dates, it looks more like something for
 the RA8x/RA6x 
This actually applies to MSCP, so it is used on both RQDX controllers, 
as well as SDI and others.

...
  The stuff at the end would be BAD144 data, or did
 they stop using that when they switched to MSCP? 
BAD144 predates MSCP, and MSCP do not use BAD144. With BAD144, the bad 
blocks of a media are visible to the system, and needs to be dealt with 
by the OS itself. With MSCP bad blocks do not exist. They are hidden 
(replaced) by the disk controller in combination with the disk itself, 
so that the OS never sees any bad blocks.

(But the actually operation of mapping out a bad block might require 
handling by the OS, depending on the controller.)

	Johnny