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FreeDOS on SBC188 (Announce)

posted by Rugxulo Homepage, Usono, 13.09.2020, 22:16

Resident FreeDOS guru Eric Auer writes via private email:

> The BTTR thread about that self-designed PC needs more
> details... For example, the PC designer could post the
> version numbers, md5sums, binaries, sources of the used
> kernels and boot sectors. The self-designed BIOS could
> show error messages on attempts to call unimplemented
> interrupts or functions of interrupts.
 >
> The LBA version of our boot sector for FAT32 only works
> with 386, but I assume we talk about FAT16 or FAT12?
 >
> How much RAM is available? FreeDOS probably needs 256k
> or more to even boot.
 >
> A FAT16/FAT12 boot sector could show, using int 10 ah=0e
 >
> FreeDOS
 >
> err (then call int 16 ah=0, then int 19 to reboot)
 >
> It would use int 13, ah=41, bx=55aa to check for LBA
> support (if carry set or bx not aa55: none?) and use
> int 13 ah=42 or int 13 ah=2 to read sectors. Also
> int 13 ah=0 after errors.
 >
> The BTTR thread mentions a boot process showing ".", so
> it probably refers to the newer boot sector version here:
 >
> https://sourceforge.net/p/freedos/svn/HEAD/tree/kernel/trunk/boot/boot.asm
 >
> If I am not mistaken, that one needs MORE than 256k RAM.
 >
> There also is Jeremy's flexible OEM boot sector:
 >
> https://sourceforge.net/p/freedos/svn/HEAD/tree/kernel/trunk/boot/oemboot.asm
 >
> That one would only use "):" and "." as messages while
> the normal boot sector would use "Error!" and "." so
> either of the two could be in use.
 >
> An easy test for the PC builder on BTTR would be to swap
> only the KERNEL SYS files. If this fails to solve the boot
> crash, then the problem is probably in the boot sector and
> easily fixed by using another SYS, but we should also check
> whether our newest SYS has the bug :-)
 >
> If swapping KERNEL SYS however breaks the case which works
> (print FreeDOS, then load kernel) then the kernel itself is
> not working on 80186 in one of the tested kernel versions.
 >
> The screenshots show that the boot sector which says "..."
> eventually proceeds to print itself and crash, while the
> boot sector which says "FreeDOS" proceeds to successfully
> löad and boot FreeDOS kernel 2040 with FAT32, Apr 7 2012,
> "C: HD1 Pri 1 CHS 0 1 1 start 0 MB size 122 MB", FreeCOM
> version 0.82 pl 3 XMS Swap Dec 10 2003 version but after
> booting from A: not C: interestingly?

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