7 Apr
2007
7 Apr
'07
7:49 p.m.
Steven N. Hirsch wrote:
I have an extensive collection of MFM/RLL drives and
have _never_ run
across one with that interface in a 3.5" form-factor. Not sure that
anything of this sort existed. 5.25" 1/2-ht. was about as sophisticated
as they got.
I've got quite a few Rodime ones here - can't remember the model number
without going and digging them out, I'm afraid. I *think* they're 30MB.
They came amongst a pile of ex-Torch Computers stock, but I've never actually
*seen* one in a customer Torch system, so I'm not sure what (if any)
conclusion to draw from that.
The largest MFM drive ever made was _probably_ the
Maxtor 2190 at 190MB
unformatted. ISTR that there was a logical limit to the number of
cylinders due to the control protocol (or perhaps limitations in the PC
BIOSes of the time) and physical limits to the number of
sectors/cylinder and the number of platters (the 2190 had 15 or 17?)
Actually, I wondered this the other day; ESDI got a lot bigger (around 600MB I
think) but IIRC was pretty much the same interface. So quite what limited the
capacity of ST412 drives I'm not sure. I believe that cylinder seeking was
done by a sequence of single steps (rather than asking the drive: "seek to
this cylinder"), so there's probably an upper limit in the ST412 spec of how
fast step pulses can be sent (and beyond a certain size a drive will either
become slow as mole-asses, or some other timeout will come into play :-)
cheers
Jules