19 Apr
2009
19 Apr
'09
12:13 p.m.
Chuck Guzis wrote:
I also considered an "embedded sector"
solution wherein a disk would
be pre-formatted with a unique pattern) that could be easily detected
by external circuitry, conditioned by a timing window. (Isn't that
called an "Address Mark? :) )
The issues as I see them are:
- If you use the B-side of a 5.25" DSDD disc, you need something to write
that formatting
- If you add something to sync to the index marks and generate a
hard-sector "emulation" index pattern from that, you can't put a HS disc in
that drive
What about just detecting the speed of the input index pulse? If they're
turning up faster than, say, once every quarter-second, then bypass the
index-pulse multiplier. Basically have a multiplexer that allows the output to
be sourced from /Index_In, or /Index_Generated.
Whether or not the system using it would over-write
the pattern is
another issue.
True. You'd probably have to jack into WRGATE and force-disable it to stop the
address mark getting overwritten.
And you still need to build something to format these crazy discs. And I'd
appreciate it if someone was kind enough to document the format :)
But there's more than one way to skin a cat, eh?
Depends if you want the skin, the meat, or just a Mythbusters-style big
explosion... <very_big_grin> :)
--
Phil.
classiccmp at philpem.me.uk
http://www.philpem.me.uk/