RL02-USB Controller Status/Problem

[Paul Koning]

> On Apr 7, 2015, at 3:25 PM, Johnny Billquist <bqt at update.uu.se> wrote:
> 
> On 2015-04-07 20:54, Pete Turnbull wrote:
>> On 07/04/2015 19:26, Johnny Billquist wrote:
>>>> Well, yes, it's still bad, and still there, but all the RT-11 utilities
>>>> use the substitute block.
>>> 
>>> So COPY/DEV is essentially only usable for opying RT-11 disks on RT-11
>>> systems. :-)
>>> Nothing wrong with that, mind you.
>> 
>> Well, no, actually; I've been using it (under RT-11 V5.7) to copy other
>> OS disks (mainly 7th Edition Unix) because it does that perfectly well
>> :-)  When the DL.SYS driver sees a disk changed, it reads the
>> manufacturing defect list so it's still good to copy most disks.
> 
> But since the 7th edition Unix most likely do not treat the bad blocks the same way as RT-11 does (skipping bad blocks), that means blocks will get renumbered, and 7th edition will end up with a very corrupt and broken file system.
> Essentially, this will only work well if you don't have any bad blocks on the device.

Not necessarily.  I don’t know the RT11 details, but suppose it works this way: a few blocks at the end are spares.  All good blocks have their native address.  All bad blocks are redirected to one of the spares.

If so, some other file system, one that avoids the bad blocks, will work fine.  All good blocks are where expected.  The bad blocks aren’t, but those aren’t in use.  The only trouble would be if the spare region is actually used for data.  If it’s free, then you’re basically ok.

	paul