Problems with AMD64 and 8 GB RAM?

Jon Noack noackjr at
Wed Mar 30 22:00:37 PST 2005

On 03/30/05 23:49, Greg 'groggy' Lehey wrote:
> On Wednesday, 30 March 2005 at 22:27:43 -0700, Scott Long wrote:
>>Jon Noack wrote:
>>>On 03/30/05 23:14, Greg 'groggy' Lehey wrote:
>>>>On Wednesday, 30 March 2005 at 21:28:36 -0700, Scott Long wrote:
>>>>>Greg 'groggy' Lehey wrote:
>>>>>>On Wednesday, 30 March 2005 at 23:01:03 -0500, John Baldwin wrote:
>>>>>>>It would be interesting to see the contents of your MADT to see if
>>>>>>>it's trying to use a 64-bit PA for your APIC.
>>>>>>Any suggestions about how to do so?
>>>>>man acpidump
>>>>How do you run that on a system that won't boot?
>>>You said the system worked with 4 GB (albeit detecting only 3.5
> Yes, this is correct.  A number of people have explained why it only
> detected 3.5 GB in this configuration.
>>>My perception of this whole ACPI thing is that it is fixed in your
>>>BIOS (although it can be overridden by the OS).  As such, the
>>>amount of RAM you have in the machine shouldn't change acpidump
>>>results.  Is that not correct?
>>This is absolutely correct.
> Ah, so you meant to say that the output from the system running with 4
> GB memory is useful?  That wasn't in the man page you pointed to.
> What it does say is:
>>When invoked with the -t flag, the acpidump utility dumps contents of
>>the following tables:
>>...       MADT
> This may be the case, but between man page and output some terminology
> must have changed.  I can't see any reference to anything like an MADT
> there.  Does that mean that there isn't one, or that ACPI can't find
> it, or does the section APIC refer to/dump the MADT?  Here's the
> complete output of acpidump -t, anyway:
> <snip acpidump output>
> Since I don't know anything about ACPI, this doesn't say too much to
> me.  Suggestions welcome.  If the APIC section is the MADT, it looks
> as if we should update the docco.

My limited research (as in, Google) shows that the MADT was defined as 
part of ACPI 2.0:

According to your previous link the motherboard specs, it supports both 
ACPI 1.0A and 2.0.  Perhaps there is a BIOS knob to toggle between the two?


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