RL02-USB Controller Status/Problem

Johnny Billquist bqt at update.uu.se
Tue Apr 7 10:56:34 CDT 2015

On 2015-04-07 15:14, Pete Turnbull wrote:
> On 07/04/2015 11:21, Johnny Billquist wrote:
>> Sp, to get to the meat of it. No, bad blocks are not replaced, or mapped
>> away, or faked. The drive and controller can detect bad blocks, and when
>> you try to read one, you'll get an error back. Drivers try a few times,
>> and then give up, giving an error back to the user program.
>> You should not try anything different.
> Absolutely.
>> Copying RL disks with a block by block copy is not something you'd do.
>> You'd mount the disk and copy the contents.
> Actually COPY/DEV under RT-11 is commonly used, especially for non-RT-11
> packs.  I can't remember what RSX does, but RT-11 /does/ deal with the
> bad block table, by not copying the last track, and copying remapped
> blocks.

But that don't make sense. You cannot just move one block somewhere else 
because it is bad on the target device. Or just ignore a block because 
it is bad on the source device.

And "remapped" must be something very local to RT-11. RSX do not remap 
any blocks. A block that is bad, is bad. It is still there. No other 
block is substituted for the bad block. And where would those 
substitution blocks come from? There are no hidden extra blocks on an RL 

RSX simply deals with bad blocks on an RL pack by making sure no file 
accidentally gets them, by putting all the bad blocks into a specific 
file on the file system, intended to hold bad blocks.

>  But in general, under other OSs, yes, not a good idea.  It
> would be like using dd in Unix to copy an entire device, including the
> disk label, rather than the partitions.



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