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Path: sserve!manuel!munnari.oz.au!uunet!bcstec!galileo!dmp3592 From: dmp3592@galileo.rtn.ca.boeing.com (Dean M. Phillips) Newsgroups: comp.unix.bsd Subject: Re: Endless boot cycle- suggestions? Summary: Watch out for geometry translation Message-ID: <1072@galileo.rtn.ca.boeing.com> Date: 19 Aug 92 16:28:05 GMT References: <Aug.14.12.34.42.1992.8037@action.rutgers.edu> <45240001@hpycla.kobe.hp.com> <Aug.18.17.41.42.1992.4915@action.rutgers.edu> Organization: Boeing Commercial Airplane Group, Seattle Lines: 45 A disk drive which does geometry translation will hopelessly confuse 386BSD. Background: MessDOS has a hard limit of 10 bits for a cylinder number. This prevents MessDOS from accessing cylinders beyond 1023. Most large hard disks have more than 1024 cylinders. So, to make these disks useable with MessDOS, the disk drive manufacturers invented geometry translation. The way this works is the drive says that it has more heads than it really does, and less cylinders than it really does, so that the total number of sectors comes out the same but with less than 1024 cylinders. When MessDOS asks for a particular track, sector, and cylinder, the drive silently translates this to the real location. "Brain damage begets brain damage." 386BSD gets the geometry and its partition info from the partition table and then TURNS OFF GEOMETRY TRANSLATION. If geometry translation was on in the first place, 386BSD will get hopelessly lost, fail to find its disk label and panic. Solution: Make sure that geometry translation is turned off. I was able to do this by running setup, specifying drive type 47 and keying in the real number of heads, etc. If you don't know what your disk's real geometry is, you can find out with a little hacking. I will post a patch when I get mwrite to work. Disclaimer: Not all reboot cycles are caused by geometry translation. On my system, it would still work with geometry translation if I let 386BSD have the whole disk. This is because the disk label is located on cylinder 0, head 0, sector 2 for both the real and the translated geometry. -- ---------------------------------------------------------------------- #include <standard_disclaimer.h> Dean M. Phillips (206) 393-9333 Boeing Commercial Airplane Group dmp3592@galileo.boeing.com