[syslinux] Re: Problem with FreeDOS + himem64 + PXELINUX + memdisk

[Patrick J. LoPresti]

The following reply was sent only to freedos-devel.  I do not know the
answers to his questions (although I suspect the "keeppxe" flag has
something to do with it).

Any help would be appreciated.  Feel free to CC
freedos-devel at lists.sourceforge.net.

 - Pat


From: Eric Auer <eric at CoLi.Uni-SB.DE>
Message-Id: <200401262148.WAA03293 at gnome.at.coli.uni-sb.de>
To: freedos-devel at lists.sourceforge.net
Subject: [Freedos-devel] re: Problem with FreeDOS + himem64 + PXELINUX + memdisk
Date: Mon, 26 Jan 2004 22:48:36 +0100 (MET)
Lines: 48


Hi Pat, are you sure that you do not for example have a virus on
that system? Well, maybe it is just the PXE software but:

> Old dos memory at 0x8fc00 (map says 0x9f800), loading at 0x8f400
> old: int13=e1f74d1a  int15=f000f859
             **** Something in the UMB / ROM area hooks BIOS disk int

Further, the "old DOS memory" information tells us that according to
int 15, 638k of 640k (rest is BIOS EBDA I guess) should be avail, but
that actually 63k less than that are available in low memory. MEMDISK
then allocates 2k more there.

> Ramdisk at 0xfe60000, length 0x00168000
> e820: 0000000000100000  000000000fef0000  1
> e820: 000000000fff0000  000000000000ec00  3
> e820: 000000000fffec00  0000000000001400  4
> e820: 00000000fff80000  0000000000080000  2

Not sure how to read this, but looks like for example you have some
59k used at the end of the first 16 MB - maybe an overlay of some sort,
special disk driver, ROM, BIOS data area for suspend...? Then there are
5k more to round up to 16 MB. Finally you have 512k of something much
later, maybe a framebuffer or something. The MEMDISK (again, if I do
understand things right) uses 1.5 MB at the end of the first big chunk
in the first 16 MB. This seems to overlap other things, but I do not hope
that MEMDISK would have such an obvious bug...

As I do not know whether I have to subscribe to SYSLINUX for mailing there
and as I do not know whether it has address hiding in a possible web archive,
I am not CCing SYSLINUX at zytor - but feel free to forward.

Hope this is not a too unqualified posting... Maybe PXELINUX or some BIOS
or driver thing is an easy explanation for the extra memory areas, and
maybe I misinterpreted the int 15.e820 information completely and there is
no overlap, but you never know 8-].

Eric