[GLLUG] Laptop Hard Drive

[Thomas Hruska]

Charles Ulrich wrote:
> On Wed, 2007-08-29 at 19:44 -0400, Patrick Collora wrote:
>> Hey Everyone,
>>
>> My mother gave me her old Micron/Zeos Pentium laptop, which has an 800 
>> MB drive.  I'd like to install one with a higher capacity, but I'm not 
>> certain what it can support.  After searching the web I found that there 
>> are a number of potential BIOS limitations, but I haven't found a way to 
>> verify whether they are present or not other than to try a drive and see 
>> what happens.  Unfortunately, the largest 2.5" drive I own is the 2 GB 
>> one in my 486 notebook, which I'm sure this one can support as well.  Do 
>> any of you have any extra laptop drives I could test in it?  Barriers 
>> around 4 and 8 GB appear to be common, so I'd like to test one larger 
>> than 8 GB.  I wouldn't mind putting some more RAM in it also, but 
>> unfortunately the modules appear to be proprietary, so I may not be able 
>> to find any.  I'll probably be able to come to the meeting tomorrow, for 
>> a little while at least.
>>
>> Thanks.
> 
> If you're going to run Linux on it, BIOS disk size limitations don't
> matter. If you attach a 500GB drive to a BIOS that only supports a
> maximum of 8GB, the BIOS will only see an 8GB drive. But Linux will see
> the whole thing because it doesn't access the drive through the BIOS.
> The only real limitation is that you can't boot off any partitions
> higher than the 8GB boundary. Which is fine because most boot partitions
> are written to the front of the disk.

I'm pretty sure the 8GB limit doesn't apply on most modern BIOSes:

http://home.teleport.com/~brainy/diskaccess.htm

I've heard modern GRUB (possibly LILO) can boot from anywhere whereas 
previous incarnations had the 8GB limitation:

http://www.gnu.org/software/grub/grub-legacy-faq.en.html


Here's something really interesting:

http://www.ata-atapi.com/hiwtab.htm

A large gap of 254 sectors at the start of the hard drive immediately 
following the MBR (roughly 130K).  130K is a bit tight, but there is 
enough space to cram, well, pretty much anything - you just need a bit 
of code and a lightweight driver for the hard drive that has /boot. 
Dealing with the partition table is simple enough:  Point it at the next 
sector where part of a boot loader resides and use a different table to 
boot from that can handle any drive size.

It seems somewhat odd that most OSes just leave that section of the hard 
drive completely unused.

-- 
Thomas Hruska
CubicleSoft President
Ph: 517-803-4197

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