11 Jan
2021
11 Jan
'21
6:21 a.m.
On Jan 9, 2021, at 4:55 PM, David Gesswein via cctalk
<cctalk at classiccmp.org> wrote:
On Sat, Jan 09, 2021 at 01:06:19PM -0700, Warner Losh wrote:
DEC Std 144 is for older disks, not MSCP. It is the format for telling the OS where the
bad sectors are, so the file system creation tool can mark those sectors as unavailable.
That doesn't involve remapping (at least not on the OS I know). The bad sectors still
exist in the address space, they are just not free so they won't be used.
The MSCP revectoring is a more complex mechanism where the controller tweaks the logical
block numbering address space so it appears to be error-free. I assume it's a
generalization of the spare-sector feature of the RM80, but as others have pointed out,
with MSCP this was an internal matter of the controller and I don't know of any DEC
standard for it. In fact, the details are likely to depend on the properties of
individual drives.
paul
DEC standard 144 of any help?
http://bitsavers.org/pdf/dec/standards/EL-00144_B_DEC_STD_144_Disk_Standard…
Warner
Thanks for looking.
That standard is only capable of marking bad sectors. It doesn't have the
information on where the bad sectors were remapped to. I took a quick look
at the DSM image. It looks like cylinder 511 is where the controller
tables are. This cylinder does have a different format. The data didn't
match this standard.