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When I built my home desktop five years ago my AMD M4A88TD-V motherboard had 4x2GB GSkill DDR3 RAM. When I would click on Computer->Properties, it would say 8GB installed, 7GB usable.

Tonight I upgraded memory to 4x8GB GSkill DDR3 SDRAM.

When I power up 64-bit Windows 7 and click on Computer->Properties, it says 32GB installed but only 16GB usable.

Is this a limitation of my motherboard? Or is there a BIOS setting that I need to change? (I'll check memory remapping per this answer.)

Hennes
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duffymo
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    If it is this one, it only supports 16GB: https://www.asus.com/Motherboards/M4A88TDV_EVOUSB3/specifications/ – Paul Dec 17 '15 at 01:14
  • D'oh! Should have checked. – duffymo Dec 17 '15 at 01:15
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    Sometimes a bios update will allow more memory. Read the notes carefully as some Raid drivers need to be updated after bios upgrade. https://www.asus.com/Motherboards/M4A88TDV_EVOUSB3/HelpDesk_Download/ – Moab Dec 20 '15 at 00:50
  • Thank you @Moab, but the link you cited is the EVO motherboard. That's the one I'd have to upgrade to in order to address all my memory. I appreciate your effort, though. – duffymo Dec 20 '15 at 14:35
  • Thats all google returned when searching AMD M4A88TD-V – Moab Dec 21 '15 at 00:25
  • And that all that shows on the Asus site https://www.asus.com/search/results.aspx?SearchKey=AMD%20M4A88TD-V – Moab Dec 21 '15 at 00:26
  • My motherboard is five years old. It's probably not made anymore. – duffymo Dec 21 '15 at 00:51
  • I found out that my motherboard does allow 32GB of RAM without a BIOS upgrade or any other changes. It was the hobbled operating system that was the problem all along. – duffymo Feb 06 '16 at 22:55

2 Answers2

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Many motherboards have this limitation - the vendor just saved cost by not connecting more address lines, assuming that it wouldn't matter ever (there are years between motherboard design and productive use, so it's difficult to predict what is normal when it's ready for selling).

I actually paid full 400 $ more - just last month - for my ASUS laptop (with otherwise equal specs) just to have the ability to upgrade memory to 32 GB (and I did not spend another 800 $ to be able to upgrade to 64 GB...). So, chances are, your motherboard does not allow it. You should be able to find this in the vendor's specs, they don't advertise such limitations in the large-print, but they do have them in the spec.

Aganju
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  • Turns out that it wasn't the motherboard, it was the operating system. Upgrading to Windows 7 Professional did the trick. – duffymo Feb 06 '16 at 22:57
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If you're running Windows 7 Home Premium, then the operating system is limiting you to 16GB usable RAM.

More here: 16 GB of my 32 GB of memory is unusable, marked as "hardware reserved"

Community
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Andy McKenzie
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  • How about quoting the relevant information? – Ramhound Jan 29 '16 at 19:23
  • This was the right answer. I realized that my motherboard was detecting 32GB of installed RAM. I found a copy of Windows 7 Professional on eBay, upgraded, and now I have all of my installed RAM available to me. It was simple, thanks to you. – duffymo Feb 06 '16 at 22:54