Dne 06. 08. 22 v 19:30 Peter Stuge napsal(a):
> Kevin O'Connor wrote:
>>> SeaBIOS can be used for booting legacy OS and also Linux is still using
>>> CMOS address 0x10 to configure floppy controller. Under these assumptions
>>> it makes sense to allow boot from CMOS defined floppy drives.
>>
>> There was never really a standard for the layout of CMOS nor for the
>> encoding of floppy type.
>
> Ralf Brown's interrupt list disagrees:
>
> --8<-- CMOS.LST
> ----------R10--------------------------------
> CMOS 10h - IBM - FLOPPY DRIVE TYPE
> Note: a PC having a 5 1/4 1.2 Mb A: drive and a 1.44 Mb B: drive will
> have a value of 24h in byte 10h. With a single 1.44 drive: 40h.
>
> Bitfields for floppy drives A/B types:
> Bit(s) Description (Table C0007)
> 7-4 first floppy disk drive type (see #C0008)
> 3-0 second floppy disk drive type (see #C0008)
>
> (Table C0008)
> Values for floppy drive type:
> 00h no drive
> 01h 360 KB 5.25 Drive
> 02h 1.2 MB 5.25 Drive - note: not listed in PS/2 technical manual
> 03h 720 KB 3.5 Drive
> 04h 1.44 MB 3.5 Drive
> 05h 2.88 MB 3.5 drive
> 06h-0Fh unused
> SeeAlso: #C0007
> -->8--
>
I agree, these will be probably used by older OSes and having the floppy type
to be able to change without reflashing is definitely useful.
>
>> Currently, SeaBIOS doesn't use CMOS for anything when configured for
>> coreboot mode and I think we should keep it that way.
>
> The first either 15 or 48 bytes are explicitly reserved on all
> coreboot mainboards and coreboot checksums bytes 16-45 when built
> to use an option table.
>
>
>> If you have a machine with a floppy drive that you'd
>> like to use with coorboot+SeaBIOS then you can set the "etc/floppy0"
>> or "etc/floppy1" cbfs files to activate support in SeaBIOS.
>
> That's fine, but why reject the de-facto standard method?
>
Also few other bytes (14h) in this range could be used by legacy OSes too.
>
> Kind regards
>
> //Peter
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