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Adding large disk support to INT13h (Users)

posted by bretjohn Homepage E-mail, Rio Rancho, NM, 04.04.2024, 19:33

> That for sure is correct. To be specific, EDD-2.1 is supported.
EDD back as far as version 1.1 (I have a copy of the spec) supports 64-bit LBA. If yours isn't doing that, it doesn't _really_ support EDD.

> I am using these functions right now with FDISK in LBA mode.
If you're using FDISK and EDD works, why do you say it doesn't work?

> ...
> Therefore I want to substitute the INT 13 routines, and not the BIOS as a
> whole (which btw. is more than INT13).
The BIOS is indeed more than INT 13h and is also more than disks. But INT 13h is the BIOS interface to the outside world for disk-related items.

If you end up writing your own, you'll need to do it at the hardware-specific level (PATA, SATA, etc.). While that's possible to do, it defeats the purpose of having a BIOS.

> ...
> Well, the disks get only detected as 8.4GB in the BIOS setup screen, and
> there is no way for me to manually enter larger sizes. CHS access will NOT
> fail because of cylinder values >1023, because there is no exposed cylinder
> 1023.
The "standard" setup for disks larger than 8.4 GB is to set CHS to the maximum 8.4 GB (CHS = 1024-256-63). That is supposed to work as a "flag" that tells the rest of the world (including the BIOS) that the disk is actually larger than 8.4 GB. Does that not work for you?

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