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Hello Daniweb yet again I have returned! This time with a rather weird issue...

My latest custom build PC has 6Gb of Corsair RAM, but my copy of Windows 7 Pro x64 says "6.00Gb (4.00Gb usable)"

Any ideas? I have gone through the internet to look for various solutions but no one seems to be able to provide a straight answer. Windows's Memory Test comes up with no errors what so ever, and in Task Manager it only reads there being a total of 4Gb as 'usable'. Any ideas why the other 2Gb decides not be used? Re-seating the RAM does work, but upon reboot it then decides to revert back to this message.

Any ideas anyone?

Serunson, out.

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Dani AI

Generated

reported that the problem cleared after reseating the CPU and enabling a RAM profile in the BIOS. That combination points to two common root causes on X58 systems: intermittent contact or a disabled memory channel (the memory controller sits in the CPU on LGA1366), and BIOS/voltage/timing mismatches that prevent all DIMMs from being mapped correctly.

Why this happens: a bad electrical contact (socket pins, uneven cooler pressure, or a partly-seated CPU) can make one memory channel appear and disappear across reboots. Separately, BIOS memory profiles (XMP/JEDEC) set the correct voltage and timings; if those are wrong the board may remap or reserve portions of RAM so Windows reports only 4 GB usable. Also check that the motherboard’s memory-remap feature is enabled so a 64-bit OS can see the full address space; without it some address ranges are reserved for PCI/MMIO and become unusable.

Quick checklist to follow (do these in order):

  • Verify Windows is really 64-bit and that 4 GB usable is not an OS/boot option issue.
  • Update the motherboard BIOS to the latest stable revision.
  • Inspect CPU socket visually before reseating: look for bent pins and avoid forcing components; ground yourself and follow the manual.
  • Confirm cooler mounting is even; excessive torque can flex the board and break contacts.
  • Populate DIMMs exactly per the manual (A1/B1/C1 then A2/B2/C2 for triple channel) and test one stick at a time to isolate bad DIMM or slot.
  • Enable memory remapping and load a safe memory profile (or set JEDEC defaults), then test stability.
  • Run a bootable memory tester such as Memtest86+ for several passes to rule out module faults.

If the board still only shows 4 GB after these steps, suspect a hardware fault (socket, CPU, or motherboard northbridge) and contact Gigabyte support or pursue RMA.

Member Avatar for Serunson

In case anyone else gets this issue - resit your CPU, and enable Profile1 in the RAM settings in the BIOS. Has fixed mine after 5 reboots (touch wood).

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