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My current set up is below

enter image description here

I bought this computer build from a 3rd party, they self built it. I reinstalled windows.

At the time I did not know about Home edition not recognizing all 24 GB ram. So when I finally got it working it said, 16 GB usable, 24 GB installed.

I bought the upgrade to professional and it went from 16 GB to 24 GB installed.

Now I have restarted the computer and it does not recognize the 24 GB RAM, it does not even say it's installed, just that 16 GB RAM is installed.

Fixes I've tried:

  • Boot Menu and making sure Memory is unticked and at 0,
  • BIOS does not recognize it,
  • Re-seating the RAM to no avail.

How do I get all 24 GB of RAM recognised and working?

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  • Possible duplicate of: superuser.com/q/50138/180465 or superuser.com/q/27086/180465
    – Jet
    Aug 2, 2015 at 16:34
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    run memtestx86 if it does not show up in there then you have a dead stick.
    – Ramhound
    Aug 2, 2015 at 16:39
  • "BIOS does not recognize it," says it all.
    – Moab
    Aug 2, 2015 at 17:01
  • After running memtestx86 I will conclude that the two sticks are most likely dead. I find it odd they both died at the same time and only worked for 3-4days after upgrade to Win Pro 7. Thank you for your help.
    – Shan
    Aug 2, 2015 at 17:21
  • @Shan those sticks might not be dead. look at my answer below.
    – Keltari
    Aug 2, 2015 at 17:33

1 Answer 1

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First off, you fixed the first issue of upgrading Windows 7 to the Professional version. Windows 7 Home only supports up 16GB on x64 hardware. Windows 7 Professional, on x64 hardware supports up to 192GB of RAM.

Secondly, I googled your motherboard. My first assumption, was that your MSI MS-7666 did not support 24GB of RAM. However, it does. The manual shows that it supports 6 DDR3 DIMMs of the following type: DDR3 2133*(OC)/ 1800*(OC) /1600*(OC)/ 1333/ 1066 / 800DRAM, with a max of 24GB.

At that point, I assumed you were having a hardware issue. Either you had bad memory, or a bad memory controller. However, something nagged at me and then I googled your processor.

Your Intel® Core™ i7-990X Processor Extreme Edition supports 24GB of RAM, however that is only if the memory is DDR3 1066.

My feeling is not all your RAM is DDR3 1066. Take all your memory out and hopefully, the stickers tell you the type and speed. If not, you might have to google the part numbers. If any of them are not DDR3 1066, they will not let your machine support 24GB of RAM.

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  • I am pretty sure that memory type frequency is the minimum not the maxmium because literally every CPU I have ever looked at on Intel's website gives the same number.
    – Ramhound
    Aug 2, 2015 at 17:45
  • I have seen this issue before, granted it was only on server hardware.
    – Keltari
    Aug 2, 2015 at 19:02

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