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LZ-DOS 7.1 *IS* MSDOS 7.1 (Miscellaneous)

posted by tom Homepage, Germany (West), 22.11.2007, 12:39

> > Neither of those are particularly appealing to me, especially since I've
> > already proven this is the MS-DOS kernel (or the 0.0000001% chance that
> > it's merely reverse engineered & stolen code, which is no better).
>
> You proved that the small kernel loader is the same as in MS-DOS 7.10 (as
> is by the way the boot sector whose work it continues), but you can't
> prove anything about the real kernel itself until you can unpack it.
Lucho, I know that you don't accept the concept of 'copyright', but that
does mean you may act just stupid (or just lazy).

LZDOS can be easily unpacked - by booting it.

what I did:
create a MSDOS 7.1 floppy with
IO.SYS
command.com (freedos)
mem.exe (freedos)
debug.com (freedos)
autoexec.bat (empty)
config.sys (just containing DOS=LOW)

create a LZDOS 7.1 floppy with IO.SYS replaced by 'LZDOS' IO.SYS

boot this 2 maschines to compare

a:>MEM
says 488 KB free (DOS is loaded low) in both cases. so what ?

a:>MEM /D
lists addresses of all devices in the system. *ALL* devices are at the
same address. That's interesting, but maybe a really undocumented
secret requires that.

OK, lets look at the devices themself; lets look at the code of
the COM4 device handler (mem /d has provided the address).

a:>debug
-d 70:DC

strange, looks identical on both maschines.
take the 4'th word; it's the address of COM4->interupt handler
u 70:2b8
...

still identical, so the conclusion is inevitable:
the COM4 'interrupt' handler is identical (instruction for instruction),
which for me ends this discussion.

if you want to prove *YOUR* point (that LZDOS is created by some sibirian
genius),

do the same for the CON device, CLOCK device, or any other device.
disassmble the INT 21/INT 2f handler, and show us any (significant)
difference.

otherwise just admit, that this genius just removed some MS startup screen,
and compressed the MS 7.1 kernel (which is remarkable and welcomed,
nevertheless)

I hope that ends this war, and we can get back to technical issues.

Tom

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