RE: memory detection problems: 2.0.x vs. 2.2.x

nathan.zook@amd.com
Mon, 6 Dec 1999 15:29:49 -0600

Okay, this looks like the problem we are having with some Athlon boards. My
guess is that the board supports ACPI, which includes SMAP (int 15/e820) for
memory reporting. Depending on the configuration, SMAP compliance may
require that int 15/e801 memory reporting change. At least one bios vendor
has decided to remove int 15/e801 memory reporting instead, which is
permitted. 2.2.x does not support SMAP (although it may, if I can get
things together), so we end up with int 15/88 reporting.

POSSIBLE FIX: It may be that if ACPI is turned off, int 15/e801 reporting
is restored. Since 2.2.x does not support ACPI, this should not result in
any performance degredation. If this does not work, you are stuck with
using mem=XXX.

WARNING: Using mem=XXX, where XXX is the total ram, may lead to undefined
behavior in SMAP systems. Leave at least 1M at the top of RAM for system
reserved space. If you use a bios with integrated video, leave 1M + video
ram space.

MAXIMUM SAFETY: Install a kernel version >2.3.18, and look at the top of
/var/logs/dmseg for the output of the e820 calls. Setting mem=XXX is
equivalent to telling the system that all of the memory from 1M to XXX is
available for use. You can safely use the ACPI memory (type 3), but
RESERVED and NVS memory must not be used. Do not specify mem=XXX if XXX is
above the start of the first RESERVED or NVS region.

Nathan

-----Original Message-----
From: roel@grobbebol.xs4all.nl [mailto:roel@grobbebol.xs4all.nl]
Sent: Monday, December 06, 1999 2:51 PM
To: Khimenko Victor
Cc: set@pobox.com; linux-kernel@vger.rutgers.edu
Subject: Re: memory detection problems: 2.0.x vs. 2.2.x

On Sun, Dec 05, 1999 at 05:36:15AM +0300, Khimenko Victor wrote:
> Linux 2.2 uses new int 15 subfunction to detect more then 64MiB of RAM
(and
> fallback to old method if that subfunction is not there) and you have
broken
> BIOS where that same call is used for completely other purpose. That's
all.

the abit BP6 NJ release has changed this function apparently -- my MB
doesn't report the correct amount of memory right now.

could you (privately) tell me where I can find this call and params so that
I can ask abit to fix this ?

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