From: ajb8886@ritvax.isc.rit.edu
Subject: Re: NEED:cylinder/sector information for FUJI FK309-39R disk drive
Reply-To: ajb8886@ritvax.isc.rit.edu
Organization: Rochester Institute of Technology
Distribution: usa
Date: Sun, 11 Oct 1992 16:43:08 GMT

In article <r=5-fN@engin.umich.edu>, magilla@engin.umich.edu (Reid Doyle Erickson) writes:
>Hi,
>
>I have a PC-XT with a 32 meg Fuji HDD that has bitten the dust.  I don't
>have any documentation on the drive itself, but I believe that the model
>is an FK309-39R.  If someone has information about this drive, specifically
>the number of cylinders and sectors per track, I would appreciate the help.
>

My reference manual doesn't list a FK309-39R (my manual is a little out of
date).  Closest match I could find was the FK305-39, and the FK305-39R 
(@ 615 cyls * 6 heads each).

If your drive >really< is 32MB (and not a larger capacity), then it's extremely
likely that the parameters would be one of the following:
      MFM drive : 614 cyls * 6 heads * 17 sectors/track (32MB)
      RLL drive : 614 cyls * 4 heads * 26 sectors/track (32MB)


I'm not sure, but I do believe that the 'R' extension on the Fuji part
number denotes an RLL rated drive (vs. MFM rated).


>Also, what is the difference between MFM and RLL drives (I looked for a FAQ
>listing in this group, but couldn't find one, so no flames please)?  

The difference between MFM and RLL drives is how the data is coded on a given
cylinder.  MFM divides the drive into 17 sectors per cylinder per head, with
512 bytes per sector.  (the number of tracks is the number of cylinders *
heads).  

An RLL (also referred to as 2,7 RLL) records at 50% higher data density per
track, or 26 sectors/track instead of 17.  Because of the higher data density,
for a given interleave the RLL controller also has a data transfer rate 50%
faster.

Also note that a given RLL or MFM drive are pretty much the same; the only
difference is that an RLL-rated drive is designed for the 50% higher data
density per track, and the 50% higher data transfer rate.  

The controller itself determines the actual format; an MFM controller would
format 17 sectors per track, irregardless of whether it is connected to an MFM
or RLL drive; conversely, an RLL controller will format 26 sectors per track,
irregardless of whether an MFM or RLL drive is connected.  Thus arose the
practice of trying to use RLL controllers with MFM drives to get 50% more space
and 50% higher capacity while paying for the MFM 'size'.  Certain MFM-rated
drives would indeed work flawlessly and error free formatted as RLL ; but there
are a few exceptions, so experiment at your own risk.  (Personally, I've
been using a control data 72MB MFM drive formatted as RLL to 109 MB for quite
a few years now without a single problem.)

Note that most XT controllers, whether MFM (unless they are VERY old MFM
full-length controllers such as the ones in the original IBM PC/XT) or RLL
generally have a routine in their BIOS extension you can call directly to
prepare the drive's low-level format prior to FDISK (partitioning) and FORMAT
C:/s (dos-level format).  For most non-ancient MFM or RLL controllers, the
optimum interleave is either 4:1 (or in the case of adaptecs 3:1).  If your
controller card isn't full length (ie. it's just a squarish card that doesn't
extend all the way back), you can usually assume it's fairly recent.

To access the routines on the BIOS ROM extension:
run DEBUG.COM from one of your dos diskettes.

at the debug prompt '-' type
- g = c800:5

If a menu comes up, then all is well.  If it freezes, reset and try again
with one of the following jump addresses :
 g = c800:ccc (for adaptec controllers)

 g = cc00:5 (rare)

 g = d800:5 (sometimes set this way)


Hope the info helps.

If you have any other questions, feel free to ask.

Alex



>
>I don't normally read this group, so please send all replies via e-mail.
>
>Thanks in advance,
>
>Reid
>
>(magilla@caen.engin.umich.edu)
Newsgroups: comp.sys.ibm.pc.hardware