[clug] Overriding the BIOS' impression of a disk

Andrew Pollock andrew-clug at andrew.net.au
Tue Oct 28 17:58:44 EST 2003


I've got an antediluvian motherboard that I recently discovered (the hard 
way) couldn't handle a disk >32Gb

This is after a bought a 120G disk at the fair to reinstall it with. So I 
bought a 40G disk on the weekend and set the jumper to limit the size to 
32G and just wore the loss of 8G. Motherboard was happy, booted Linux, and 
I was happy.

Until I booted the kernel and saw:

hda: Host Protected Area detected.
        current capacity is 66055248 sectors (33820 MB)
        native  capacity is 78165360 sectors (40020 MB)

and this got me thinking about some of the kernel parameters, and I went 
reading ide.txt in the kernel documentation and found:

Drives are normally found by auto-probing and/or examining the CMOS/BIOS 
For really weird situations, the apparent (fdisk) geometry can also be 
specifiedon the kernel "command line" using LILO.  The format of such 
lines is:
or      hdx=cdrom
where hdx can be any of hda through hdh

So this got me wondering as to whether I could jumper the 120G drive to 
32G so the BIOS will boot it, and then append the real geometry to the 
kernel and then I could have my cake and eat it?

Before I go pulling apart multiple machines *again* I thought I'd ask here 
if anyone else has done this successfully?



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