Discussion:
Legacy Firmware/INT 13H supporting >512 byte sectors?
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Mihai Moldovan
2018-08-17 14:59:06 UTC
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Hi


Just a quick question: did anyone ever come up a BIOS firmware that supports
sector sizes higher than 512 bytes (say 4096 bytes)?



Mihai
Vladimir 'phcoder' Serbinenko
2018-08-17 16:11:21 UTC
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Post by Mihai Moldovan
Hi
Just a quick question: did anyone ever come up a BIOS firmware that supports
sector sizes higher than 512 bytes (say 4096 bytes)?
Sure. Any BIOS able to read CD supports 2K sectors.
If you mean HDD then I have never seen one. I wrote support for non-512B
sectors in GRUB but so far it's untested as I couldn't find such a BIOS
Post by Mihai Moldovan
Mihai
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Mihai Moldovan
2018-08-17 18:01:11 UTC
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[resent to list, since I forgot to add a CC header]
Post by Vladimir 'phcoder' Serbinenko
Sure. Any BIOS able to read CD supports 2K sectors.
If you mean HDD then I have never seen one. I wrote support for non-512B sectors
in GRUB but so far it's untested as I couldn't find such a BIOS
Ah, of course. CD sectors are 2K big. Yeah, that makes sense.

I meant HDD sectors, yes.


My firmware is doing weird things: it always reports a sector size of 512 bytes,
reads and outputs data in 512 byte chunks, but sector addressing is actually
HDD-dependent (i.e., for 4Kn drives 4K-based).

I'll work around that using some heuristic, but that's only part of the problem.


The bigger issue will probably be the boot image, which likely is too small to
incorporate sophisticated code. I guess I could trick THAT into behaving
correctly by spreading the core image file out over several sectors and only
using the first 512 bytes of each sector.



Mihai
Toomas Soome
2018-08-17 18:07:46 UTC
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Post by Mihai Moldovan
[resent to list, since I forgot to add a CC header]
Post by Vladimir 'phcoder' Serbinenko
Sure. Any BIOS able to read CD supports 2K sectors.
If you mean HDD then I have never seen one. I wrote support for non-512B sectors
in GRUB but so far it's untested as I couldn't find such a BIOS
Ah, of course. CD sectors are 2K big. Yeah, that makes sense.
I meant HDD sectors, yes.
My firmware is doing weird things: it always reports a sector size of 512 bytes,
reads and outputs data in 512 byte chunks, but sector addressing is actually
HDD-dependent (i.e., for 4Kn drives 4K-based).
I'll work around that using some heuristic, but that's only part of the problem.
The bigger issue will probably be the boot image, which likely is too small to
incorporate sophisticated code. I guess I could trick THAT into behaving
correctly by spreading the core image file out over several sectors and only
using the first 512 bytes of each sector.
Yes there are systems supporting BIOS INT13, see https://www.illumos.org/issues/8303 <https://www.illumos.org/issues/8303> for reference.

rgds,
toomas

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