XP memory detection problem at 4 GB


E

Eddie

Hi Everyone,

I have an Athlon Fx-53 (939) system with 4GB of dual-
channel memory filling the memory banks of an Asus A8V
motherboard.

For some reason XP doesn't seem to detect the full 4GB of
memory installed. In the System Information tool it
claims a "Total Physical Memory 2048.00MB" and "Available
Physical Memory of 2.64GB", which is incorrect (not to
mention seemingly illogical).

The system's BIOS, drivers, and windows patches have all
been updated. I've checked the memory settings in the
BIOS and the only setting that seemed to be relevant (the
others were all related to timings and bank/node
interleaving) was the "4GB mapping" setting, which I
toggled between enabled and disabled and got different
but incorrect results (with it disabled System
Information claimed a "Total Physical Memory 2048.00MB"
and "Available Physical Memory of 3.16GB", with it
enabled it was as above).

I have also installed the XP 64-bit beta and it returns
similar, yet different again, results. With the 4GB
mapping enabled, System Information claimed a "Total
Physical Memory 2048.00MB" and "Available Physical Memory
of 3.28GB", while disabled it claimed a "Total Physical
Memory 2048.00MB" and "Available Physical Memory of
2.85GB" -- very strange results.

What makes these results even more strange is that the
BIOS claims 4096MB of memory, the CPU-Z application
claims 4 DIMMS of 1GB, SiSoft Sandra's System Summary
tool claims 4096MB of total memory. Also, Windows Task
Manager claims a total physical memory of 3144948 bytes
and an available physical memory of 2769732 bytes...very
strange.

Perhaps Windows views a dual-channel pair as a single
DIMM? If so, why does it say there is 3.16GB of
available physical memory?

To be honest, it matters little what all these tools
report. What I'm concerned with is whether the system
actually has access to all four GB and how I can ensure
this is the case. This system is intended to run
scientific simulations and all four GB of memory are very
necessary. Any help would be greatly appreciated.

Thanks,

Eddie
 
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C

Carey Frisch [MVP]

How to Use the /USERVA Switch in the Boot.ini File to Tune /3GB Configurations
http://support.microsoft.com/default.aspx?scid=kb;EN-US;316739

Correct your boot.ini file:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /3GB /Userva=2900

Windows XP SP1 May Not Start with the /3GB or /USERVA Switch
http://support.microsoft.com/default.aspx?scid=kb;en-us;328269&Product=winxp

"Stop" Error Message When You Start Windows XP by Using the /3GB Switch
http://support.microsoft.com/default.aspx?scid=kb;en-us;829364&Product=winxp

--
Carey Frisch
Microsoft MVP
Windows XP - Shell/User

Be Smart! Protect your PC!
http://www.microsoft.com/security/protect/

-----------------------------------------------------------------------------------


| Hi Everyone,
|
| I have an Athlon Fx-53 (939) system with 4GB of dual-
| channel memory filling the memory banks of an Asus A8V
| motherboard.
|
| For some reason XP doesn't seem to detect the full 4GB of
| memory installed. In the System Information tool it
| claims a "Total Physical Memory 2048.00MB" and "Available
| Physical Memory of 2.64GB", which is incorrect (not to
| mention seemingly illogical).
|
| The system's BIOS, drivers, and windows patches have all
| been updated. I've checked the memory settings in the
| BIOS and the only setting that seemed to be relevant (the
| others were all related to timings and bank/node
| interleaving) was the "4GB mapping" setting, which I
| toggled between enabled and disabled and got different
| but incorrect results (with it disabled System
| Information claimed a "Total Physical Memory 2048.00MB"
| and "Available Physical Memory of 3.16GB", with it
| enabled it was as above).
|
| I have also installed the XP 64-bit beta and it returns
| similar, yet different again, results. With the 4GB
| mapping enabled, System Information claimed a "Total
| Physical Memory 2048.00MB" and "Available Physical Memory
| of 3.28GB", while disabled it claimed a "Total Physical
| Memory 2048.00MB" and "Available Physical Memory of
| 2.85GB" -- very strange results.
|
| What makes these results even more strange is that the
| BIOS claims 4096MB of memory, the CPU-Z application
| claims 4 DIMMS of 1GB, SiSoft Sandra's System Summary
| tool claims 4096MB of total memory. Also, Windows Task
| Manager claims a total physical memory of 3144948 bytes
| and an available physical memory of 2769732 bytes...very
| strange.
|
| Perhaps Windows views a dual-channel pair as a single
| DIMM? If so, why does it say there is 3.16GB of
| available physical memory?
|
| To be honest, it matters little what all these tools
| report. What I'm concerned with is whether the system
| actually has access to all four GB and how I can ensure
| this is the case. This system is intended to run
| scientific simulations and all four GB of memory are very
| necessary. Any help would be greatly appreciated.
|
| Thanks,
|
| Eddie
 
G

Guest

Hi Carey,

Thanks for you help. I tried what you recommended but to
no avail. Nothing changed at all with respect to my
original post. When System Information (and Task Manager
for that matter) display the total physical memory, is it
read from the BIOS or does it have it's own method of
determining what the physical memory amount is? Does XP
see a dual-channel pair as a single DIMM? Is there
another way I can test/tell whether all 4GB are actually
going to be used by the system?

If anyone else has an answer or suggestion please feel
free to post.

Thanks,

Eddie


-----Original Message-----
How to Use the /USERVA Switch in the Boot.ini File to Tune /3GB Configurations
http://support.microsoft.com/default.aspx?scid=kb;EN- US;316739

Correct your boot.ini file:

[boot loader]
timeout=30
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft
Windows XP Professional" /fastdetect /3GB /Userva=2900
 
B

Bob Day

Eddie said:
Hi Everyone,

I have an Athlon Fx-53 (939) system with 4GB of dual-
channel memory filling the memory banks of an Asus A8V
motherboard.

For some reason XP doesn't seem to detect the full 4GB of
memory installed. In the System Information tool it
claims a "Total Physical Memory 2048.00MB" and "Available
Physical Memory of 2.64GB", which is incorrect (not to
mention seemingly illogical).

Right click on the task bar at the bottom of your Windows XP
screen and click on "Task Manager", then on the "Performance"
tab. What does it say for "Total" under "Physical Memory (K)" ?

-- Bob Day
http://bobday.vze.com
 
E

Eddie

Hi Bob,

It says 3144948. So it's only showing around 3 GB.

I think this might be related to the memory map. XP only
sees a 4GB memory map, but my bios has a setting DRAM
over 4G Remapping. What this seems to do (based on what
I've seen from running memory diagnostics) is that it
takes the last GB of 4GB of memory to the map above the
4GB boundary. So we have,
----------------------
| 0-3072 | 4096-5120 | equalling 4GB total,
----------------------
instead of,
----------
| 0-4096 |
----------

This is why I only see 3GB in XP with this set (i.e. the
first map section). When I don't have this BIOS setting
enabled one would think that I would get all four GB
before the first boundary, but nope, Windows and the
memory diagnostics see,
----------
| 0-3584 | , so it shows 512MB less than 4GB.
----------

I don't know if this is a mobo issue or what, but for
some reason the full 4GB cannot fit in the first map.
Has anyone else had any experience with 4GB of memory
behaving in this way?

I'd appreciate any help,

Eddie
 
N

Nathan McNulty

A 32bit processor cannot address over 4 GB of memory. Your 64bit
processor can address up to 64 GB of memory
(http://www.lostcircuits.com/cpu/amd_a64fx51/3.shtml).

I have seen this problem on similar setups, but most of them have been
because of BIOS shortfalls. Just a thought, maybe try updating your
chipset drivers.

As for Windows only showing 2048 MB of memory, you are correct in
assuming that sometimes Windows views Dual Channel as one module per
channel. This means that your 4 GB shows up as 2 GB. This can usually be
fixed by a BIOS update, but in your case, you already tried this :(
 
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N

Nathan McNulty

There is no setting in XP 32bit to allow XP to see beyond the 4GB
threshold. If you want to have Windows see beyond that, install a 64bit
version of Windows XP. Also, large amounts of memory are a known
problem for XP. There are so many factors that can cause improper
displaying of memory size it makes it difficult to pinpoint the actual
problem. It could be the BIOS, it could be the chipset, it could be the
memory itself, it could be an actual Windows setting such as the
finetuning of the boot.ini file by adding /3GB to the string. Many
things could be causing this.
 

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