This article is from a FAQ concerning SCO operating systems. While some of the information may be applicable to any OS, or any Unix or Linux OS, it may be specific to SCO Xenix, Open There is lots of Linux, Mac OS X and general Unix info elsewhere on this site: Search this site is the best way to find anything.
This is a combination of TA 482436 and a procedure posted in comp.unix.sco.misc by a hardy adventurer. Use it at your own risk; it may not work with all hard drives, and you may not be able to have other OSes on your hard drive in some cases. Note also that there is an SLS, uod429a, which adds LBA support to 3.2v4.2, and should be used instead of this procedure where applicable.
OpenServer Release 5 is the first SCO operating system which supports LBA (Logical Block Addressing) mode, so to install on an older system the first thing you need to do is to disable this mode. This may involve jumpers or a BIOS setting change; check your hardware documentation.
Configure your BIOS to believe the hard drive has 1024 cylinders, 16 heads, and 63 sectors per track. Begin your installation, and make sure you run through the disk initialization section manually. Apparently, if you can select the "Preserve additional filesystems" option, this may be an easy way to do it. When you get the prompts dealing with the actual geometry of your hard drive (this program is dkinit), modify the current disk parameters, and set them to something larger. At 16 heads and 63 above) spt, every actual megabyte (1 048 576 bytes, or 1024 kB) of disk space takes about two cylinders; you could use this equivalence to calculate the number of cylinders you should enter. If in doubt, guess low; you do not want to have Unix trying to use disk space which isn't there.
When you've done this, you've basically told Unix to ignore the BIOS settings (which will be used only for booting), and that should lift the ~500 MB limit up to about a gig. Note that there is a limit of 2048 cylinders in SCO's hard drive drivers, which means you will not be able to access more than about a gigabyte.
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