Largest ST-506 (MFM or RLL) type HDD?

Philip Pemberton classiccmp at
Wed Oct 14 15:45:23 CDT 2009

Hi guys,
   Does anyone know what the largest capacity MFM or RLL (i.e. 
ST-506/ST-412 type interface) hard disk was? I know the AT drive types 
go from 0 to 46 (plus user defined type 47), and the largest of these is 
  #46: 1224 cyls, 15 heads, 17 secs (152MB). Question is, did anyone 
ever make an MFM drive that big, or was that strictly IDE territory?

   I know 80MB and 120MB IDE drives existed -- I used to have a Conner 
120MB that was an utter pig to make work with any other drive, and I 
still have an IBM WDA-L80 80MB IDE drive. Thus far, the largest MFM 
drive I've found is the Micropolis 1325 (85.3Mbytes unformatted).

   Reason I'm asking is that I'm working on the seek logic for the disc 
analyser. At the moment, you can seek 127 cylinders at a time in either 
direction (there isn't a track-counter on the hardware, so all seeks are 
relative) and I was wondering if there's any point in increasing this 
further to accommodate drives with higher track counts.

classiccmp at

More information about the cctech mailing list