paul@cs.utexas.edu (Supoj Sutanthavibul) (08/23/90)
Is 1024 the maximum number of cylinders that dos 4.01 can handle? What should I do if I have a drive with more than 1024 cylinders? supoj
prs@io.UUCP (Paul Schmidt) (08/28/90)
In article <11478@cs.utexas.edu> paul@cs.utexas.edu (Supoj Sutanthavibul) writes: >Is 1024 the maximum number of cylinders that >dos 4.01 can handle? What should I do if I have a >drive with more than 1024 cylinders? 1024 is the maximum number of cylinders a standard, compatible _BIOS_ can handle. With the appropriate device drivers, I should think that virtually any version of DOS could handle larger drives. I expect that when you purchase a large drive, that the supplier should provide a compatible device driver.
scjones@thor.UUCP (Larry Jones) (08/30/90)
In article <1742@io.UUCP>, prs@io.UUCP (Paul Schmidt) writes: > 1024 is the maximum number of cylinders a standard, compatible _BIOS_ > can handle. With the appropriate device drivers, I should think that > virtually any version of DOS could handle larger drives. I expect that > when you purchase a large drive, that the supplier should provide a > compatible device driver. Rumor has it that the next release of DOS after 5.0 will provide support for disk with more than 1024 cylinders. ---- 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 I always have to help Dad establish the proper context. -- Calvin
bmarsh@cod.NOSC.MIL (William C. Marsh) (08/31/90)
In article <145@thor.UUCP> scjones@thor.UUCP (Larry Jones) writes: >In article <1742@io.UUCP>, prs@io.UUCP (Paul Schmidt) writes: >> 1024 is the maximum number of cylinders a standard, compatible _BIOS_ >> can handle. With the appropriate device drivers, I should think that >> virtually any version of DOS could handle larger drives. I expect that >> when you purchase a large drive, that the supplier should provide a >> compatible device driver. > >Rumor has it that the next release of DOS after 5.0 will provide >support for disk with more than 1024 cylinders. 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. Bill -- Bill Marsh, Naval Ocean Systems Center, San Diego, CA {arpa,mil}net: bmarsh@cod.nosc.mil uucp: {ihnp4,akgua,decvax,dcdwest,ucbvax}!sdcsvax!nosc!bmarsh "If everything seems to be coming your way, you're probably in the wrong lane."
scjones@thor.UUCP (Larry Jones) (09/03/90)
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