Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!cs.utexas.edu!uunet!sdrc!thor!scjones From: scjones@thor.UUCP (Larry Jones) Newsgroups: comp.os.msdos.misc Subject: Re: Max cylinder in DOS 4.01? Keywords: DOS 4.01 Message-ID: <150@thor.UUCP> Date: 2 Sep 90 22:12:46 GMT References: <11478@cs.utexas.edu> <1742@io.UUCP> <145@thor.UUCP> <2086@cod.NOSC.MIL> Distribution: usa Organization: SDRC, Cincinnati Lines: 36 In article <145@thor.UUCP> I wrote: > Rumor has it that the next release of DOS after 5.0 will provide > support for disk with more than 1024 cylinders. In article <2086@cod.NOSC.MIL>, bmarsh@cod.NOSC.MIL (William C. Marsh) writes: > I can't see how this could be accomplished, since the BIOS interface is > limited to 10 bits for cylinder address (and, for that matter, the WD1003 > chip set had the same limitation) > > It is the controller manufacturer who needs to provide the driver/support > for more than 1024 cylinders. With sector mapping, WD, Adaptec, and DTC > support more cylinders, but even with sector mapping this still leaves a > maximum of 512M per drive. Right -- it's the BIOS interface that currently limits disks to 1024 cylinders. All modern disk controllers are already capable of handling it. Unfortunately, the BIOS is usually on the motherboard rather than being supplied with the controller, so the controller manufacturers can't really change it, and there's no point since DOS wouldn't use it anyway. I presume that what is going to happen in DOS 5.1 (or whatever) is that DOS will officially adopt one of the extended INT 13 interfaces that uses some of the currently unused bits here and there for extra cylinder address bits (On Track's BIOS extension for Disk Manager works this way and I presume Speed Stor does something similar). Whether DOS will also include a replacement for the BIOS's INT 13 routine like it already does for floppy drives or if they just leave it to Phoenix, AMI, Award, and friends to do their own updates, I don't know. ---- Larry Jones UUCP: uunet!sdrc!thor!scjones SDRC scjones@thor.UUCP 2000 Eastman Dr. BIX: ltl Milford, OH 45150-2789 AT&T: (513) 576-2070 Life's a lot more fun when you're not responsible for your actions. -- Calvin