12 Oct
1999
12 Oct
'99
1:11 p.m.
Ok, so not as much as at 7:00 this morning... HD media
has a higher
coercivity, thus requires more write current to put a bit on the
disk. If you use that much write current with LD media (lower
coercivity) you will get a larger bit. The larger bit will partially
overwrite adjacent bits, leading to low amplitude, and read errors.
The "bit" size has more to do with the gap and physical construction of
the head, as I remember from my magnetics courses. Yes, the current
is obviously interrelated, but the primary factor is the head gap.
Ok, I wasn't aware of any 96tpi drives except the
HD ones... Were
they ever used in the PC marketplace, or was it mostly a DEC thing?
Yes, there were a few not-quite-100%-PC-compatible clones that used
DD media at 96 TPI. There were even 100 TPI drives, just to be incompatible
with nearly everybody! (Well, they also eked out a bit more capacity
from the same media, which was a selling point when few
had hard drives.)
After re-reading my uVAX manual about the RX50, I agree
it is a
96tpi single sided drive, though the manual says: "Use only formatted
RX50 diskettes, available from DIGITAL or its licensed distributors"
So there are four drives using the same media:
SSDD 180K,48tpi,40tracks/side
DSDD 360K,48tpi,40tracks/side
RX50 360K,96tpi,80tracks/side
???? 720K,96tpi,80tracks/side - What was (is) this called? DSQD?
Some aftermarket third-party DEC-compatible controllers have a
double-sided RX50 mode that they call "RX52".
--
Tim Shoppa Email: shoppa(a)trailing-edge.com
Trailing Edge Technology WWW: http://www.trailing-edge.com/
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