Problems with AMD64 and 8 GB RAM?

John Baldwin jhb at
Thu Mar 31 05:39:19 PST 2005

On Mar 31, 2005, at 12:27 AM, 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:
>>>>>> On Mar 30, 2005, at 8:54 PM, Greg 'groggy' Lehey wrote:
>>>>>>>> lapic0: LINT1 trigger: edge
>>>>>>>> lapic0: LINT1 polarity: high
>>>>>>>> lapic1: Routing NMI -> LINT1
>>>>>>>> lapic1: LINT1 trigger: edge
>>>>>>>> lapic1: LINT1 polarity: high
>>>>>>>> -ioapic0 <Version 0.3> irqs 0-23 on motherboard
>>>>>>>> +ioapic0 <Version 0.0> irqs 0-23 on motherboard
>>>>>>>> cpu0 BSP:
>>>>>>>>   ID: 0x00000000   VER: 0x00040010 LDR: 0x01000000 DFR: 
>>>>>>>> 0x0fffffff
>>>>>>>> lint0: 0x00010700 lint1: 0x00000400 TPR: 0x00000000 SVR: 
>>>>>>>> 0x000001ff
>>>>>> This shows that in the - case the APIC is broken somehow (0.0 
>>>>>> isn't a
>>>>>> valid I/O APIC version).
>>>>> You mean the + case, I suppose.  Yes, that's what I suspected.
>>>>>> It would seem that the system has mapped RAM over top of the I/O
>>>>>> APIC perhaps?
>>>>> That's what I suspected too, but imp doesn't think so.
>>>> I'd be more inclined to believe that there is an erroneous mapping
>>>> by the OS, not that things are fundamentally broken in hardware.
>>> Agreed.  This has been my favourite hypothesis all along.  But isn't
>>> that what jhb is saying?
>>>> Your SMAP table shows everything correctly.  It's becoming hard to
>>>> break through your pre-concieved notions here and explain how things
>>>> actually work.
>>> No, there's nothing to break through.  I think you're just having
>>> problems
>>> 1.  expressing yourself, and
>>> 2.  understanding what I'm saying.
>>> I have no preconceived notions.  All I can see here is an 
>>> antagonistic
>>> attitude on your part.  What's the problem?  You'll recall from my
>>> first message that I asked for suggestions about how to approach the
>>> issue.  jhb provided some; you haven't so far.  From what you've
>>> written, it's unclear whether you disagree with jhb or not.  If you
>>> do, why?  If you don't, what's your point here?
>>>>>> 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 GB).  
>> 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?
>> Jon
> This is absolutely correct.

It might though.  Notice the change in APIC version with 4GB of RAM vs 
8GB.  The APIC hardware is the same, so that's already indicative of 
something fishy going on.  I think that his APIC address is correct 
though as otherwise no interrupts at all would work and it wouldn't 
claim to have 24 IRQs on the APIC in both cases.  One can always boot 
an i386 non-PAE kernel with 8GB in the machine and get an acpidump 


John Baldwin <jhb at>  <><
"Power Users Use the Power to Serve"  =

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