Re: IDE disk geometry + patch

Gerhard Mack (
Fri, 4 Dec 1998 12:12:24 -0800 (PST)

Please be carefull, last time changes like that were made it killed my

This is a WD Caviar 2100 with no translation enabled. hda1 is mounted as
/boot this way I can avoid translation since on as some of the setups I've
installed on have buggy translation that is noticably slower (IPC

I've had had to haul out bootdisks twice, in the deval series over changes
such as the one being discussed.

output from cfdisk:

Heads: 16 Sectors per Track: 63 Cylinders: 2100

Name Flags Part Type FS Type Size (MB)

/dev/hda1 Primary Linux 5.42
/dev/hda2 Primary Linux Swap 20.18
/dev/hda3 Primary Linux 1008.00

On Fri, 4 Dec 1998 wrote:

> From Fri Dec 4 06:19:55 1998
> The reason the IDE driver does NOT do what you suggest
> is to ensure 100% compatibility with the BIOS view when
> using programs (like LILO and fdisk) which interact with
> the BIOS.
> The code is very careful to correctly use the BIOS view
> of the drive under such circumstances, and it is a little
> too risky to try changing it at this stage of
> (it could break many systems through some unforeseen interaction).
> Hmm. It sounds like you react without thinking.
> Look at the code I want to replace. It corrects bios_cyl
> under certain circumstances. I want to correct bios_cyl
> under a wider set of circumstances.
> It is not at all the case today that the Linux kernel
> preserves the BIOS view on the number of cylinders.
> Now think about the fdisk and LILO interaction.
> What is the effect of a too small number of cylinders?
> That part of the disk is inaccessible.
> For LILO one may live with that - there have always
> been restrictions on the place of the kernel on disk.
> But for fdisk that is inacceptable - people struggle
> with this, and - as far as I can see - there is no
> reason at all to inflict these problems unto them.
> The number of people with 8+ GB disks increases quickly.
> The handling of large IDE disks has always been broken,
> but in 2.0.35 and 2.1.90 this problem was partially
> corrected by inserting the test for C/H/S=16383/16/63.
> However, this only solves the problem if the BIOS is
> not using a translation (`LBA' or `Large' or so).
> People with a large IDE disk and translating BIOS
> still cannot use the entire disk (without overriding
> the kernel view by giving LILO additional hda=C,H,S
> parameters, or going into expert mode of fdisk, etc.).
> The sooner this is corrected, the better.
> Andries
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Gerhard Mack

As a computer I find your faith in technology amusing.

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