MFM/RLL data recovery

From: "Vintage Computer Festival" <vcf at siconic.com> Sent: Monday, April 04, 2005 6:14 PM With Vintage as a domain name you should be familiar with the fact that standards develop slowly. Hard drive interfaces for the PC "standardized" with the AT, before that people did what ever they wanted. Sometimes one controller would read a disk from a different type of controller but it was just luck. Most hard disk controllers formatted to 17 sectors of 512 bytes per track but that doesn't say much about how it is formatted at the hardware level (bit for bit). Another point is that before the AT the drive geometry was normally kept on the drive and different controllers stored the information differently. With the PC many people hooked up drives before the XT came out but once IBM came out with the AT they had chosen a "standard" hard drive controller everyone worked to emulate until RLL controllers came out. Even controllers like the Everex controllers that did track buffering to allow 1:1 interleave were still "compatible" with the AT formatting. If you have an MFM drive used on an AT or better you have a good chance of reading it on any AT or better system with most any controller. RLL or 8 bit based systems have no such "standard". Randy www.s100-manuals.com