Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!zaphod.mps.ohio-state.edu!sol.ctr.columbia.edu!ira.uka.de!ifistg!ifi!boegehol From: boegehol@informatik.uni-stuttgart.de (Harald Boegeholz) Newsgroups: comp.sys.ibm.pc.hardware Subject: Re: ESDI harddisk >512MB: WHY is there a 16head-limit? Message-ID: Date: 23 Nov 90 10:52:12 GMT References: <2351@sixhub.UUCP> Sender: news@ifistg.uucp Distribution: comp Organization: IfI, Univ. Stuttgart, W Germany Lines: 19 In-reply-to: davidsen@sixhub.UUCP's message of 23 Nov 90 02:21:10 GMT In article <2351@sixhub.UUCP> davidsen@sixhub.UUCP (Wm E. Davidsen Jr) writes: In the header on each sector there is a 2 byte field which holds the cylinder number in 12 bits, and the head number in 4 bits. Therefore you can't write a header for a head number > 15 or a cylinder number > 4096. The second doesn't seem to be a problem today. What kind of header do you mean? The one physically recorded on the hard disk? I'm not converned with that (at least I don't want to be :-) ). The hard disk needs to be remapped (by the controller) anyway, and I'd like to know why there can't be more than 16 heads _after_ remapping. At least I haven't found an ESDI controller that can do it. I thought the DOS mapper packages took care of this. You pay a penalty in performance by using the mapping. Yes, but I want to use OS/2! Harald Boegeholz