I suspect the problem is just the boot sector.
There are tools which will write various boot sectors (possibly including freedos' sys command).
The issue might simply be compatibility, or attaining the correct 512b boot sector file.

This might help
https://teaching.idallen.com/dat2343/09f/note … skStructure.htm

It seems that this guy had a similar problem, he used a real MS-DOS 4 floppy to get correct boot sector:
https://www.youtube.com/watch?v=BR6F0EdyulA

Azarien wrote on 2024-05-22, 08:26:

It seems that this guy had a similar problem, he used a real MS-DOS 4 floppy to get correct boot sector:
https://www.youtube.com/watch?v=BR6F0EdyulA

I watched that video and the Freedos video on compiling DOS 4 from source beforing starting on this. While using an existing system disk in the process would work, the ideal would be to generate the bootable image from scratch.

myne wrote on 2024-05-22, 05:32:

I suspect the problem is just the boot sector. There are tools which will write various boot sectors (possibly including freedos […]
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I suspect the problem is just the boot sector.
There are tools which will write various boot sectors (possibly including freedos' sys command).
The issue might simply be compatibility, or attaining the correct 512b boot sector file.

This might help
https://teaching.idallen.com/dat2343/09f/note … skStructure.htm

You are correct, writing a boot sector is the problem (or more specifically writing a boot sector that boots DOS 4). I did get Freedos's sys.com to write to a floppy image using the build's io.sys file in place of the freedos kernel but the resulting image did not boot. Using sys with the Freedos command interpreter and kernel on the disk image boots in the VM, as does a random DOS 4 install disk from the Internet Archive, so I know I can create a bootable thing and I know I can boot the target OS, I just need to make a bootable thing that boots with the target OS.

I wonder how installing a development build worked back in the day; someone would have had to install the first DOS 4.0 system for the first time....

https://home.mnet-online.de/willybilly/fdhelp … rd/base/sys.htm

/oem:Ms ?

myne wrote on 2024-05-22, 14:18:

https://home.mnet-online.de/willybilly/fdhelp … rd/base/sys.htm

/oem:Ms ?

It would be awesome if that was the case. The documentation online for Sys.com has /oem:ms listed but the command itself doesn't seem to support it and I can't tell if the executable is newer and the functionality removed or if the executable is older than the documentation. If it's the latter, then I need to hunt down a new freedos kernel package.

I did find a copy of the 512 bytes MS DOS writes to the boot sector of a disk in the source itself (boot.inc). The media type descripter is not correct but if I munge that together with a blank formatted disk image, the VM at least starts booting from floppy and then hits the error handler in the boot disk that display's the boot disk's "non-system disk" error, which feels like progress. At this point it seems like either I need to alter the bootloader code to point to where io.sys is located or locate io.sys to where the bootloader expects it.

wouldn't it be possible to remove the dos version check from sys, and use that to write the bootsector and other files(io,msdos,command) to disk ?

Seems easier to do it that way
or if freedos has some functionality like SETVER , use that

weedeewee wrote on 2024-05-22, 18:04:

wouldn't it be possible to remove the dos version check from sys, and use that to write the bootsector and other files(io,msdos,command) to disk ?

Seems easier to do it that way
or if freedos has some functionality like SETVER , use that

Freedos has the "callver" command which works in terms of allowing executables to run, but the DOS 4 tools like FORMAT and SYS running from Freedos seem confused either by what the virtualized hardware is telling it or confused by their interactions with the Freedos kernel. I already tried that approach and it did not seem to pan out.

Attached GDB to QEMU and did hbreak at *0x7c00.

Looks like the C/H/S calculation for the sector to read from disk is wrong:

----------------------------[ CPU ]----
AX: 0201 BX: 0500 CX: 0002 DX: 0100
SI: 6027 DI: 7C49 SP: 7BF6 BP: 0000
CS: 0000 DS: 0000 ES: 0000 SS: 0000

=> 0x7d90: int 0x13

Basically, the VM is about to call interrupt 13h function 2 to read 1 sector from cylinder 0, sector 2, head 1. I don't think that is right so something is messing up the calculation from sector number to a c/h/s tuple (CH/DH/CL or 0/1/2)

Hopefully I can track down the errant byte sequence...

Why do you think that's wrong, e.g. what LBA do you think that will attempt to read vs. which LBA should it be reading? The sector parameter for that BIOS call is based at 1, not 0... so the head parameter is what you should probably be focusing on but without knowing how the disk is partitioned it's impossible to say if it's correct or not.

Are you sure /oem doesn't work?

It's still in there. Typo? Case sensitive?

https://github.com/FDOS/sys/blob/master/docs/sys.txt

myne wrote on 2024-05-23, 02:59:

Are you sure /oem doesn't work?

It's still in there. Typo? Case sensitive?

https://github.com/FDOS/sys/blob/master/docs/sys.txt

The OEM arg is present in the SYS.COM distribute d on the FD13Full live image but supports fewer options. I might try to pull the newer version and build it and give that a shot.

It hasn't changed in over 10 years. Just how much newer can it be?

myne wrote on 2024-05-23, 05:02:

It hasn't changed in over 10 years. Just how much newer can it be?

I hear you, it looks like the /oem:ms option is part of a feature set that is not enabled by default (https://github.com/FDOS/kernel/blob/master/sys/sys.c#L34).

Looks like the source tree for sys.com as a standalone is not used and sys.com is compiled with the freedos kernel.

so using sys with the additional OEM types enabled at compile time worked! now to wrap it all up with something to package up some disk images and I'll have myself a regular DOS factory.

Seems weird to disable it, but whatever.
Glad it's working.

Now you've made the first, you've chicken and egged it, right? You can use 4.0 sys now.