🚀 go-pugleaf

Tim Jackson (tim_jackson@bigfoot.com) wrote:
> The other day I had a nasty hard drive crash (power cable came loose).
> I ended up with a bad block (when validating the drive, AmigaDOS
> reported an error on that block; unfortunately I've forgotten what it was
> but it wasn't something like a checksum). DiskSalv couldn't fix it so I
> had a look at HDToolbox to try to map the block out. However, HDToolbox
> asks for:
>
> Cylinder:
> Head:
> Sector or Bytes from Index:
>
> How do I convert a block number (32708 or something) to the appropriate
> values?  I guess it will depend on the BlocksPertrack etc. (DiskSalv gives
> you all those kind of values) but I don't really know enough about the
> physical layout of HDs to work it out.

The trouble with someone like me answering a question like this is that
there's a fair chance that I'm completely wrong :-(

You'll have to make your own mind up on that.

In the case of my particular HD, HDToolBox tells me that there are 15
heads, 63 blocks per track.  That gives 63x15=945 blks per cyl, which
makes sense, because I supposedly have a total of 8940 cylinders (even
though I can't use them all), giving 4.3GB.

So: typically, the last block error *I* got was blk 1089826.
Divide by 945, gives cylinder 1153, remainder 241 (blks)
Divide remainder by 63 (bl/track) gives head 3, remainder 52 (blks).

So it's cylinder 1153, head 3, blk 52.

HOWEVER, I'm pretty sure that when DOS reports the error it is talking
about a specific partition.  It surely has to be, because I've had errors
which, if the given block no is absolute, fall far below the named
partition. IYSWIM.

So you need to add the start cylinder for that partition.  In my case that
was cyl 558, giving 1711/3/52.

If you tell HDToolBox the Cylinder and Head, it'll work out the other
thing for itself.

I did this, and it hasn't failed since, but that of course doesn't mean
that I'm right -- it could just be that DOS hasn't tried to use that area
since for some secret reason of its own :-)

Suck it and see, I guess ....

DaveB