On Wed, Jul 15, 1998 at 03:26:00PM -0400, Richardson,Anthony wrote: > On Wed, 15 Jul 1998, Nils Rennebarth wrote: > >The last sentence is wrong. In case of LBA, BIOS as well as LILO to use > >linear sector numbers. The conversion is made in the drive itself, in a > I'll stand by my last sentence based on the LILO documentation and my > understanding of disk access through the BIOS (which comes from The > Undocumented PC). Ok. I stand corrected. > When LBA mode is enabled in the BIOS, the BIOS converts the CHS > address to an LBA one to talk to the disk. In summary, programs > communicate to the BIOS using CHS, if LBA is enabled the BIOS communicates > to the disk using LBA. The BIOS has to convert the CHS address to an LBA > one. The "linear" LILO option doesn't solve or fix anything. It causes > sector addresses to be written to the map file in LBA form. At boot time > LILO gets the CHS geometry from the BIOS and converts the LBA addresses to > CHS ones so that it can call the BIOS routines to read sectors from the > disk. (The BIOS then converts this to LBA to communicate with the disk if > LBA is emabled.) If I understand this correctly, LILO gets a fake geometry from the bios, at boot time, uses this to convert linearly numbered sectors to CHS form. The BIOS takes this CHS form, converts it back to a linear number again and uses this to talk to the drive. This at least guarantees (barring grossly faulty BIOSes) that the linear number LILO starts with is the same that is finally communicated to the drive. (What a mess btw.) > I'd rather get the geometries to match not only for LILO but also for > fdisk/cfdisk. fdisk is important if you are also running DOS on the same > machine. But I never had problems with fdisk nor cfdisk and big harddrives. And I never specified any geometry anywhere. I would like to mention that I do have a lot of old mainboards around, that will be put to good use eventually, using Linux of course, and very much appreciate the fact that it is possible to still use those with larger disks. Some of them even do not even have a flash eprom, so BIOS upgrade isn't an option. But you shouldn't scare newbies that usually have modern hardware away with all these talks about geometries, 1024 cylinders etc. Nils -- *-----------------------------------------------------------------------------* | Quotes from the net: L> Linus Torvalds, W> Winfried Truemper | | L>this is the special easter release of linux, more mundanely called 1.3.84 | | W>Umh, oh. What do you mean by "special easter release"?. Will it quit | * W>working today and rise on easter? *
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