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  Asus P5B only sees 3 GB of 2x2GB PC6400 [SOLVED] 
 
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Reason   Apr 14, 2009, 04:22pm EDT Reply - Quote - Report Abuse
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Edited: Oct 21, 2010, 05:44pm EDT

Replies: 7 - Views: 13702
Has 4 slots, manual says 8 GB capable. I was running 2x1 + 2x512 for a total of 3. I swapped out the 2x512 for the 2x2 and started Memtest. Memtest only showed 5 GB, wtf?

Further testing shows that either 2GB stick will show as 2GB in any slot when installed alone, but if I put both 2GB sticks in, the BIOS only shows 3 GB.

Where it gets even weirder is that I booted into Windows with both sticks, and CPU-Z recognizes both sticks as 2GB, even though BIOS (and XP) only recognize a total of 3GB.

Still have to run every possible combination of sticks + slots, and maybe a BIOS update will fix it, but has anyone run into this before?

Edit: added mobo info:
If you install four 1 or 2GB memory modules, the system may only recognize less than 3GB because the address space is reserved for other critical functions. This limitation appears on Windows XP 32-bit operation system which does not support Physical Address Extension (PAE)


That shouldn't apply to the BIOS, though, correct? And when I have all 4 slots populated, the BIOS does show 5 GB.

Edit: clarification that problem is in BIOS.


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Meats_Of_Evil Apr 14, 2009, 04:43pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
Well in the Operating system unless it's 64-bit it will only read 3gb.

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Michael C Apr 14, 2009, 05:13pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
Yep the problem looks to be in the BIOS. Either way, XP 32bit is only going to detect 3.2GB of it. Same for Vista 32bit. I have 4gb but only 3.2 is being used, sucks :(

Reason   Apr 14, 2009, 05:14pm EDT Reply - Quote - Report Abuse
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Edited: Apr 14, 2009, 05:17pm EDT

 
>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
Here's what CPU-Z shows with all 4 DIMMs installed. Those timings on Slot 1 for the Mushkin are kind of weird. I've never had any problems with that RAM, ran Memtest overnight when I got it.

http://img162.imageshack.us/img162/5078/6gb.jpg

I don't get why CPU-Z can see all 6 GB but the BIOS won't. Wouldn't it need to "go through" the BIOS to get that info? I'm pretty ignorant of low-level computer operations so I don't really know where or how CPU-Z gets its info.

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Michael C Apr 14, 2009, 05:25pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
I'm not sure either. But why do you have 6GB of ram on the 32 bit OS?

I would trust CPU-z.

Reason   Apr 14, 2009, 05:31pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
Price was right, $30 for 2x2GB of PC6400, and i might try Ubuntu 9.04 x64 and use VirtualBox when I really need XP.

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Reason   Apr 14, 2009, 08:12pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
I was googling something else and found this:

http://www.tomshardware.com/forum/255376-28-asus-issue
(User had 4x1 GB DIMMs)
With that motherboard, you have 3 options:

1. Disable Memory Remapping and have 3GB detected by the BIOS and 3GB available for Windows 32-bit;
2. Enable Memory Remapping and have 4GB detected by the BIOS and 2GB available for Windows 32-bit;
3. Enable Memory Remapping and have 4GB detected by the BIOS and 4GB available for Windows 64-bit;


Basically I can enable Memory Remapping, and the BIOS should see all of the RAM but XP will only see 2 GB. I haven't confirmed this, I'll test it later and add the result to this post.

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Reason   Oct 21, 2010, 05:43pm EDT Reply - Quote - Report Abuse
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>> Re: Asus P5B only sees 3 GB of 2x2GB PC6400
So, a year and a half later, I upgraded to Win 7 x64 and decided to add these two sticks.

Enabled Memory Remapping and installed both 2gb sticks. Got a crash/reboot loop when Windows was loading, either stick. It was late so I just reverted to my 2 x 1GB + 2 x 512 MB. The next day I re-enabled M/R and took out the 512s, rebooted, all good. Added one 2G stick, booted, all good. Added the other one, booted, all good. So it works now, although I'm a little leery of that first boot issue.

In conclusion, memory remapping!

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