13 Mar
2007
13 Mar
'07
12:17 p.m.
As hinted at in another post a few days ago, I'd like to add an 8" drive (or
possibly more than one if necessary) to my Imagedisk machine in order to be
able to archive 8" media.
My knowledge of 8" drives is practically non-existent, so what are the gotchas
involved? Things like:
Do 8" drives exist in both hard and soft sector variants? Is one far more
common than the other (as with 5.25")?
YEs, but it's not a big problem. The hard sectored drives include a
little circuit to separate the index and sector pulses, it can normally
be 'jumpered out'.
Do 8" drives exist with wildly different track counts (40, 77, 80 etc.) and
again is any one particular flavour far more common than the others?
All common 8" drives are 77 cylinder. I can well believe others were
made, but I've yet to see one.
Are there any problems with some particular drives that'll make interfacing
them to a '765 type FDC more difficult?
The biggest problem (and it only applies to writing) is the TG43 signal.
This is s signal that is Asserted _by the controller_ when the head is
closse to the spidnle that cylinder 43 (The name is Track Greater than
43, of course). It's used to reduce the write current.
A few drives generate it internally. There have been various solutioned
mentioned here (using a PIC to count step pulses, etc, for exampe) to
generate it.
-tony