Out of 12 GB, only 8 GB of RAM is usable in Windows 7 Home edition 64-bit

Question

I just installed a new 8 GB RAM along with the old 4 GB on my HP Pavilion G6 laptop. BIOS shows 12 GB RAM installed, and so is the Direct X Diagnostic Utility, but only 8 GB RAM is usable. Resource monitor says that 4 GB is hardware reserved.

Why is it so? How can I make the remainig 4GB RAM usable?

Memory SPD
-------------------------------------------------------------------------

DIMM #              1
    SMBus address       0x50
    Memory type     DDR3
    Module format       SO-DIMM
    Manufacturer (ID)   Kingston (7F980000000000000000)
    Size            8192 MBytes
    Max bandwidth       PC3-12800 (800 MHz)
    Part number     99U5428-018.A00LF 
    Serial number       2D14FF82
    Manufacturing date  Week 46/Year 15
    Number of banks     8
    Nominal Voltage     1.35 Volts
    EPP         no
    XMP         no
    AMP         no
JEDEC timings table     CL-tRCD-tRP-tRAS-tRC @ frequency
    JEDEC #1        5.0-5-5-14-19 @ 380 MHz
    JEDEC #2        6.0-6-6-16-22 @ 457 MHz
    JEDEC #3        7.0-7-7-19-26 @ 533 MHz
    JEDEC #4        8.0-8-8-22-30 @ 609 MHz
    JEDEC #5        9.0-9-9-24-33 @ 685 MHz
    JEDEC #6        10.0-10-10-27-37 @ 761 MHz
    JEDEC #7        11.0-11-11-28-39 @ 800 MHz

DIMM #              2
    SMBus address       0x52
    Memory type     DDR3
    Module format       SO-DIMM
    Manufacturer (ID)   Elpida (7F7FFE00000000000000)
    Size            4096 MBytes
    Max bandwidth       PC3-10700 (667 MHz)
    Part number     EBJ41UF8BCS0-DJ-F 
    Serial number       5A231D2B
    Manufacturing date  Week 12/Year 11
    Number of banks     8
    Nominal Voltage     1.50 Volts
    EPP         no
    XMP         no
    AMP         no
JEDEC timings table     CL-tRCD-tRP-tRAS-tRC @ frequency
    JEDEC #1        5.0-5-5-14-19 @ 380 MHz
    JEDEC #2        6.0-6-6-17-23 @ 457 MHz
    JEDEC #3        7.0-7-7-20-27 @ 533 MHz
    JEDEC #4        8.0-8-8-22-30 @ 609 MHz
    JEDEC #5        9.0-9-9-24-33 @ 666 MHz
    JEDEC #6        10.0-9-9-24-33 @ 666 MHz

does BIOS see all your memory? Does dxdiag? Have you tried rebooting? — eis, Dec 23 '15 at 07:04
Indeed, Windows 7 Home Basic has a hard limit of 8GB memory maximum, as you can see from this kb article. — eis, Dec 23 '15 at 07:07
However, if it should support, you could just try re-pairing the memory sticks (see this thread) or reattaching them (solved similar issue in this thread) — eis, Dec 23 '15 at 07:09
Yes, Bios is showing it's 12gb and also the direct x diagnostic utility showing the same. When i see in resource monitor it says 4gb is hardware reserved. — sandy, Dec 23 '15 at 07:14

score 4 · Answer 1 · answered Dec 23 '15 at 07:22

Two likely possibilities

Windows 7 Home Basic can only address up to 8GB of RAM regardless of 64 bit. If you're on Home Basic, you can't address your additional 4GB.
You have a graphics chip that shares the RAM, in which case it will allocate part of it to graphics. You can check this with the following steps:

Windows Vista and Windows 7

Press the Windows key, type Control Panel, and then press Enter. Under the Appearance and Personalization, click Adjust screen resolution. On the middle of the right-hand side of the screen, click the Advanced settings. A new window should appear with your video adapter's properties; similar to the image shown below. Your video card's memory is under the Adapter tab in the [Shared] Video Memory: section (shown below).

source

Home basic is limited to 8GB so it it definitely your first point that is the correct answer: https://msdn.microsoft.com/en-gb/library/windows/desktop/aa366778(v=vs.85).aspx#physical_memory_limits_windows_7 — Mokubai, Dec 23 '15 at 07:46
Only included point 2 as the OP hasn't confirmed what edition of Windows 7 from what I can see, only Windows 7 Home, which could be Home Premium. — Jonno, Dec 23 '15 at 08:19

Out of 12 GB, only 8 GB of RAM is usable in Windows 7 Home edition 64-bit

1 Answers1

Linked