[LinuxBIOS] 2 Terabyte Limit of BIOS/MBR

Torsten Duwe duwe at lst.de
Fri Jan 11 01:21:35 CET 2008

On Thursday 10 January 2008, Martin Marcher wrote:

> the BIOS just can't handle disks that are larger than 2TB, in

In theory a legacy BIOS should be able to at least access the first 2TB. The 
limit stems from 512 bytes block size and counting blocks in 32-bit integers, 
which is done in a classic DOS disk label, in the MBR.

>  Fine so I convert the disk to a GPT and
> off I should go. 

Does your legacy BIOS support GPT? unlikely.

> OK, now the actual question(s):
> 1) Is this problem (if I understood it right) still there with linuxbios?

LinuxBIOS itself isn't directly considered with disks besides initialising the 
controller. Look at the section "Payloads" in the wiki. Most of them are open 
source, BTW 8-)

> 2) If so what plans are there to still be able to use a >2TB disk?

Make a DOS (legacy BIOS) _partition_ of small size to boot from, at the start 
of the disk. Make sure it's consistent with the GPT label. If that does not 
help, you _need_ LinuxBIOS and a capable payload, or a guru boot setup.

> 3) Last, not least I couldn't the Tyan GT20 in the supported hardware list,
> is that true or just missing.

Tyan is LinuxBIOS-friendly, behind the scenes, if the 2865(?) board is not 
supported maybe there's a way (the S2912 is supported).

> If it's missing I'll bug Tyan about this once a month or so, in case you
> don't have the specs available to send it to you (if you want me to do
> that).

Anyone here ready to do the port?

> apologies if that is totally OT but I think I'm right here :)

Not with questions about legacy BIOSes, but with datasheets you are ;-)


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