[LinuxBIOS] ACPI NVS and last 64k-ish area of RAM?

Lu, Yinghai yinghai.lu at amd.com
Wed Oct 4 21:04:39 CEST 2006

What's your total RAM installed? 4G or more. With HW memory hole enable?





From: linuxbios-bounces at linuxbios.org
[mailto:linuxbios-bounces at linuxbios.org] On Behalf Of Alan Mimms
Sent: Wednesday, October 04, 2006 11:28 AM
To: linuxbios at linuxbios.org
Subject: [LinuxBIOS] ACPI NVS and last 64k-ish area of RAM?


We have AMD dual Opteron hardware with AMD 8131+8111 chipsets attached.
Using LinuxBIOS, we have a slight problem, that APPEARS to be related to
the last 64Kbytes of RAM.  Our kboot based environment, running in 32
bit instruction set, seems to randomly crash, and the implicated area of
memory is this last 64KB.


When we run a commercial BIOS on nearly identical hardware, we see that
that BIOS has created in the E820 table an ACPI Non-Volatile-Storage
area covering this last 64KB.  LinuxBIOS is NOT doing that; LinuxBIOS is
treating all of the space as simple USABLE space.


In trying to figure this out, we have used the AMD HDT tool to read the
last 64KB.  We (SOMETIMES) the system crashes when we read this area
using HDT.


Can someone please explain what this area is for and why it's strange to
read even using a hardware debugging tool?  Is it REALLY in use for the
ACPI NVS, and can we simply tell Linux to ignore it (map it out) by
creating an entry in E820 table so it won't be used (we don't use ACPI


Thanks very much for any information.


Alan Mimms, Senior Architect
F5 Networks, Inc.  Spokane Development Center
1322 North Whitman Lane
Liberty Lake, Washington   99019

v: 509-343-3524   f: 509-343-3501


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