Re: Seeing beyond the 1024 cylindar?

[Agustin Navarro <anavarro vip eniac com>]

On Tue, 2 Feb 1999, Fred Whipple wrote:

> All,
> 
> I realize that Linux cannot be booted from beyond the 1024'th cylinder
> on a hard disk, but can it *see* beyond that?  I've been doing an
> install on a system with a ~14.5Gb hard disk and was sure to leave room
> for Linux before the dreaded 1024.  However, when fdisking the disk I
> can't seem to peer beyond the 1024 cylinder, and fdisk reports that
> there're no more than 1024 there.  This would imply a total of about 8GB
> on the disk, but of course it's larger (and Win '95, believe it or not ,
> can see the whole thing :-)
>  ........ 

I have just had this same problem after installing a 12.7 GB HD.

To sum it up:

If you have Linux 2.0.36 and you do not plan to have windows see this drive, you
can have use the entire disk area if you:

1. Use LDA in the BIOS setup. (make sure you have a recent upgraded BIOS)
2. FDISK the HD with the COMPATIBLE WITH DOS SWITCH off (It is option c in
   FDISK)

NOTE that you will LOSE ALL the DATA  in the HD with this change and that the
boot portion of linux should still be in the first 1024 =cylinder= area.

The requirement for linux 2.0.36 and the recent BIOS comes because at sometime
time there was a patch for the BIOS and the ide driver to support > 8 GB HD

You can check before hand if you have a recent enought BIOS by looking at the
boot mesg when the kernel identifies the HD it finds. At the end of the msg it
will say something like (in may case for example):

    CHS=24704/16/63 

You should have hugh number of cylinders, and a small number of heads and
sectors, in fact they should be less that 255.

To check the ide driver, look in /usr/src/linux/drivers/block/ide.c
At arround line 610 there should be a comment with

/* very large drives (8GB+) may lie about the number of cylinders */

HTH

Agustin

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Agustin Navarro P.
anavarro vip eniac com
58.2.9630746