I have Windows 7 Home Premium (64 bit) OS installed. My motherboard is able to handle up to 32 GB of RAM.

I recently upgraded my computer to 20 GB of RAM, but the computer says installed RAM is 20 GB (16 GB usable).

I have four slots on the MB, and I installed two 8 GB RAM closest to the CPU and two 2 GB RAM on the remaining slots.

I made sure the RAM are the same (DDR3 1600 MHz)

What am I doing wrong? Why am I seeing this issue in my computer's Control Panel Home?

Just in case it matters, I also installed GTX 770 GPU 2 GB memory.

Here is the specification on my motherboard: http://www.asus.com/Motherboards/P8P67_LE/specifications/.

  • 1
    Could you post more info, like chipset and mobo? The GTX 700 series will use up to 2GB of system RAM but not unless it needs to. Sep 14, 2014 at 2:30
  • 5
    Dream on. I would personally upgrade to windows 8, which handles resources much better then windows 7 anyway AND makes the last 4GB available too. win-win situation. Sep 15, 2014 at 13:29
  • 1
    I'm so used to working with Windows 7 I don't have the patience to learn Windows 8. My parents have Windows 8 and it's been frustrating for me to use. Sep 15, 2014 at 16:30
  • 13
    FWIW it appears you don't have the optimal install for your RAM. According to the user manual for your motherboard the slots are labeled A1 (closest to CPU), A2, B1, B2 (farthest from CPU). In other words you have dual channel setup. For fastest (dual channel) operation, you should install the memory in alternating order 8GB (closest to CPU), 2 GB, 8GB, 2GB (farthest). See also Multi-channel Memory. I believe that on Intel boards, the order only affects the speed of the RAM, and does not affect the amount of RAM the OS sees.
    – chue x
    Sep 15, 2014 at 19:17
  • 1
    @MrMichael "win-win". Indeed, so to speak.
    – geometrian
    Sep 16, 2014 at 0:35

3 Answers 3


Windows 7 Home Premium supports up to 16 GB of RAM. That is why only a certain amount is showing as usable.

Your computer supports the extra RAM and does detect it. It's a licensing issue in Windows that makes it only use 16 GB at a time.

Source: Memory Limits for Windows and Windows Server Releases, Physical Memory Limits: Windows 7

  • 1
    Really? Who down voted, and why? Sep 17, 2014 at 14:52
  • You may be able to use the remaining 4GB. My MB had 12 GB installed and on Win 32 only 3-4 GB were usable. I used XFastRAM to use the remaining GB as a mounted drive. There I placed the pagefile and temporary folders / browser caches. But this was a technical limitation (32 bit vs 64 bit), while yours is a license-related issue. But maybe you could be lucky enough to find a similar alternative.
    – Daniel F
    Sep 18, 2014 at 21:36

This list represents the amount of memory that the various hardware devices installed in your system have reserved so that they can communicate with the operating system. Of course, memory reserved for hardware is essentially locked and as such is not available to the memory manager.

Typically, the amount of hardware reserved memory ranges from 10 MB to 70 MB, but it can vary depending on the system's hardware configuration and might be several hundred MBs. Examples of components that can affect the amount of memory reserved include:

  • System BIOS
  • Motherboard resources, such as I/O advanced programmable interrupt controller (APIC)
  • Sound cards or any other devices that require memory-mapped I/O
  • PCI Express (PCIe) bus
  • Video card
  • Various chipsets
  • Flash devices

Just for the verification, go to "Resource Monitor" and select the 'Memory' Tab. And look for this thing 'Hardware Reserved' which might be colored gray. It should tell how much memory is reserved for hardware (you can't release that memory).

  • 11
    I've edited in the contents of your other answer. Feel free to edit your answers to add more information, rather than posting a fresh answer. On a non-threaded format like SE, that can get VERY confusing.
    – Journeyman Geek
    Sep 14, 2014 at 6:30
  • 3
    This is true, but it's not the answer to this question. It is definitely not reserving 4 GB for the hardware. The problem is, as stated in the other answer, that the Home Premium edition of Windows 7 supports only 16 GB of RAM.
    – reirab
    Sep 16, 2014 at 15:05

click start, in RUN type msconfig then click > boot tab > advanced options > uncheck the boxes for maximum memory and CPU

Close msconfig


  • 3
    Can you explain how this answers the question? Did you read the accepted answer?
    – fixer1234
    Feb 22, 2015 at 8:05

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