On at 2024-06-02 18:19 +0200, Bernd Böckmann via Freedos-devel wrote:
5. SYS C: /FORCE:CHS
And that boots without problem on the Pocket386!
Also: you asked about FDISK /XO output. It reports "W95B INT LBA
FAT32" in the upper left corner. This is running FDISK 1.3.15.
To Jim: Are you sure you ran FDISK /XO on the Pocket386 system? If FDISK
says it detects LBA there but the LBA loader from FreeDOS doesn't work
that'd be quite the bug.
Well, this is good on the one hand, but bad on the other. It means that the
system (supposedly) supports LBA access, but the FAT32 LBA loader for a reason
yet unknown to me fails to boot the thing. LBA in general seems to be working.
Otherwise FDISK would also fail in one way or another.
Have to think about what might be the cause. Looking at the source of FAT32 LBA
loader, it passes the disk access packet to the BIOS by pushing it onto the
stack and setting SI=SP, instead of reserving some space for it in its data
area. Not exactly sure that this is a good idea, as it makes this susceptible
to stack corruption, depending on how the BIOS mishandles the packet.
The packet on the stack trick is used by some lDOS MBR/boot loaders as
well, and it generally works.
https://github.com/FDOS/kernel/blob/c0127001908405d30d90f1755ad10c1b59ea8c90/boot/boot32lb.asm#L384
The BIOS may also trash some registers...
Anyone a suggestion?
If it really turns out that FDISK /XO detected LBA support *on the
Pocket386* but the LBA loader fails, I could cough up some debugging
hints as to how to install bootable lDebug on the system then debug the
failing loader. For instance:
1. Rename kernel.sys to fdkernel.sys (exact name doesn't matter)
2. Copy ldebug.com to working drive (using CHS loader) as kernel.sys
3. Boot lDebug
4. Boot FreeDOS using "BOOT PROTOCOL FREEDOS fdkernel.sys" then "Q"
5. Write loader to file: "SYS C: /BOOTONLY /FORCE:LBA BOOTSECT.DOS"
6. Reboot into lDebug
7. Try "BOOT PROTOCOL CHAIN" and then trace the loader
You could install the FAT32+FSIBOOT loader for lDebug as well but when
you already have a working boot loader then this would just be the
possible cause of more headaches. Not impossible, but not worth it
probably. As I have oft repeated lDebug can be loaded as a number of
kernel formats, most recently including the FreeDOS and the original
Enhanced DR-DOS (v7.01.07) kernel load formats.
I will advertise the lDOS FAT32 loader more in another subsequent email.
Regards,
ecm
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