30 Aug
2006
30 Aug
'06
10:29 a.m.
On Tuesday 29 August 2006 05:27 pm, Ethan Dicks wrote:
In a PC-only context, think of this real example - the
ST-225 was nominally
a 21.4MB MFM drive. The ST-238 was nominally a 30MB RLL drive. With
the exception of manufacturer surface quality verification (checking for
bad spots), the drives are identical. If you stuck an ST-238 on an MFM
controller, it formatted to 21.4MB. If you stuck an ST-225 on an RLL
controller, if formatted to 30MB (but you might or might not have any luck
keeping your data intact, depending on how good the platters were). In
other words, it was all about the controller - the drives were,
essentially, identical.
I don't recall it being a difference in the platters, but rather one in terms
of the bandwidth of one of the read amplifier chips. My recollection is that
the MFM drives used a 5 MHz data rate while the RLL stuff used a 7.5 MHz
rate. This may have been the case only after a certain point in time,
though, I'm not sure.
I know of people who took "MFM" drives and used them as "RLL" and had
no
apparent problems, while others who tried this were either unable to get it
to work or else got it working and then all of a sudden had *no* access to
their data. There were enough scary stories going around back then that I
wasn't personally inclined to try it. I did, however, manage quite nicely
with a pair of ST251s that I used with a PerStor card, giving me roughly
156MB. Those drives worked well, and I still have them, only stopped using
them because the bearing noise got pretty bad after running them 24/7 for a
while.
--
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space, a critter that can
be killed but can't be tamed. --Robert A. Heinlein, "The Puppet Masters"
-
Information is more dangerous than cannon to a society ruled by lies. --James
M Dakin