Hi! > te> My computer BIOS INT 13 is able to access up to 4096 cylinders > te> in a hard disk. > te> by using bits 6 -7 of DH in INT 13 requests as bits 10-11 of cylinder > te> number.
I remember having a 386 (NeAT mainboard) which had this kind of BIOS feature. It means you can have 4k cylinders but only 16 (in theory 64, but at least my BIOS only allowed 16) heads. As Tom points out, this is incompatible to modern style disk access, so you will only be able to use the first 1024 cylinders with FreeDOS. There are other INT 13 extensions which allow you to use cylinder numbers of up to 65535. Those come in two flavors: One is a call which tells "add CX to cylinder number for next disk access" (int 13.ef, supported by "Ontrack Drive Rocket", "SWBIOS" and "Disk Manager", and the other just adds a constant value of 1024 to the cylinder number (int 13.ee). SWBIOS is a TSR by OnTrack. For all three special "more cylinder" things, I can tell you that they are very outdated. Please install something more fancy (e.g. newer OnTrack or EzDrive driver, which you put into the MasterBootRecord) which provides a modern LBA (all sectors on disk are just accessed by linear number, not by a position in terms of cylinders, heads and sectors) interface. I even wrote something like that myself for that 386 (must have been AMI or AWARD BIOS). It mapped access to the "second" harddisk to access to the first harddisk, after adding 1024 to the cylinder number. Very ugly but allowed me to use all of my 850 MB disk for a while (until something went really wrong and the simulated 2nd harddisk contents got screwed). Yet another reason why you should use LBA: With LBA, you can have up to 255 (+/- 1, depending on OS) heads, so with a smart LBA driver in place, even CHS based access, using translation to LBA positions, can squeeze 8 GB of disk space into the first 1024 cylinders! Much better than having 16 heads and some incompatible (even to standard partition table format) cheat to allow 4096 cylinders (to reach 2 GB instead of 500 MB). Eric ------------------------------------------------------- This SF.Net email is sponsored by: Sybase ASE Linux Express Edition - download now for FREE LinuxWorld Reader's Choice Award Winner for best database on Linux. http://ads.osdn.com/?ad_id=5588&alloc_id=12065&op=click _______________________________________________ Freedos-kernel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/freedos-kernel
