On Wed, Nov 7, 2018 at 9:09 AM <ron@ronnatalie.com> wrote:

> The DEC drivers just left off the last 72 sectors.   There was no
> provision using them for block replacement.
>
Minor update -- *no dynamic replacement provision*.  There was a standard
alone utility called BAD144 that implemented DEC Standard 144 (Bad
Blocks).   What would happen is that the format was messed with the point a
bad block at on the reserved sectors.

This scheme caused nasty performance issues because seek schedualing was
defeated; and since UNIX did not originally obey DEC STD144, the standard
UNIX scheme in those days was buy 'perfect' media.  BTW: the Ultrix team -
Fred Canter IIRC -- added support for BAD144, and I think DEC gave that
code to BSD evetually.

Clem
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