Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!yale!mintaka!ogicse!emory!hubcap!ncrcae!sellers From: sellers@ncrcae.Columbia.NCR.COM (Todd Sellers) Newsgroups: comp.sys.mac Subject: Re: Beware formating HD floppies in DSDD drives Keywords: GCR vs. MFM Message-ID: <5827@ncrcae.Columbia.NCR.COM> Date: 16 Mar 90 21:20:10 GMT References: <1567@diamond2.UUCP> <1408@bridge2.ESD.3Com.COM> Reply-To: sellers@ncrcae.Columbia.NCR.COM (Todd Sellers) Distribution: comp Organization: NCR Corp., Engineering & Manufacturing - Columbia, SC Lines: 17 [Discussion of using 800K formatted HD floppies in Apple's FDHD deleted] The problem with using an 800K formatted HD floppy in the FDHD is that they use two different recording technologies. The FDHD uses MFM (modified frequency modulation, I believe) for recording on HD floppies. It uses GCR (group coded recording) for writing on other floppies. I don't think there is any truth to the signals being stronger on one over the other. I can't believe that the erase head wouldn't be able to do its job. I do agree that it is annoying. +--------------------------------+--------------------------------------------+ | Todd Sellers | EMail to (sellers@ncrcae.Columbia.NCR.COM) | | NCR E&M Columbia | or (todd@pibtest.Columbia.NCR.COM) | | West Columbia, South Carolina | | | 29169 | | +--------------------------------+--------------------------------------------+