>>>>> "AR" == Richardson,Anthony <[EMAIL PROTECTED]>
>>>>> wrote the following on Wed, 17 Jun 1998 13:52:00 -0400
AR> 1024 is the maximum number of cylinders that may be stored in a
AR> partition table entry (10 bits). 1024 is also the maximum
AR> cylinder that can addressed using the standard BIOS
AR> routines. (With a tranlating BIOS this limits you to 8 GB, with
AR> an old BIOS the limit was 504 MB). Fortunately Linux doesn't use
AR> the BIOS functions to talk to the disk or use the CYL/HEAD/SECT
AR> addresses in the partition table to locate partitions. You can
AR> tell Linux that you've got more cylinders with the
AR> hd=cyls,heads,sects boot option. (cfdisk will ask the kernel for
AR> the disk geometry. You can also tell cfdisk that you've got more
AR> than 1024 cylinders with the -c option. See the man page.) Make
AR> sure the number of heads and sectors match the numbers used by
AR> the BIOS.
Okay, now we are getting to the meat of the problem. As you say,
Linux doesn't use the BIOS functions or C/H/S addresses to locate
partitions. That is why the kernel can see all of my disk at boot.
So why does cfdisk see only 8 GB? Why doesn't it get its info the
same way the kernel does? Why does cfdisk have to ask the BIOS for
this info?
Good to know about the -c option to cfdisk, I missed that one.
Last night I set the cylinders in cfdisk. I had two choice on what to
set:
C/H/S: 16383/16/63 (what my harddisk label says)
or
C/H/S: 1229/255/63 (the shifted equivalent. Very close to what
cfdisk reported. What Partition Magic reported.)
I chose the latter so that my Linux partition might line up with my
Win95 partition. But after I had made all my partitions, written the
partition table, and rebooted (arghh) so that cfdisk could re-read the
partition table, cfdisk would not come up because it said I had a Bad
Partition Table. Probably due to my last partition extending beyond
the 1023 cylinder boundary. So I tried fdisk and it let me in fine
and then allowed me to re-set the cylinder number. I'll try "cfdisk
-c" tonight.
AR> One note: Since most (all?) boot managers use the BIOS to load
AR> the OS, you should make sure the kernel stays under the 8 GB
AR> limit by having your root partition lie entirely under the 8 GB
AR> limit. (With an old, non- translating BIOS this limit is only
AR> 504 MB.) How do you know if you have a translating BIOS? If you
AR> can make a partition greater than 504 MB under DOS, you've got
AR> one.
Thanks, I did this.
AR> See the following for detailed info:
AR> 1) Large-Disk mini HOWTO
I read this and found it did not explain this problem very well. It
seemed geared toward the 504 MB limit. Only under SCSI does it
reference the 8 GB problem and there it give no solution.
Mark Mabry
Avici Systems
[EMAIL PROTECTED]
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