Gigabyte X58A-UD3R RAM problems
One of the most tricky hardware problems is the RAM! Problems with RAM vary from speed, capacity, chips, and brand mismatch to seating problems. A newly installed Gigabyte motherboard (X58A-UD3R) running Windows 7 Enterprise edition installed with 6GB of RAM was reporting just 4GB of usable memory. Three modules of 2GB each were installed in the correct channels that is, in the DDR3_1, DDR3_3 and DDR3_5 sockets while all modules were identical. Upon every reseating attempt, the system temporarily reported the correct amount of memory. (Reseating the RAM means with the computer switched off, you uninstall and install back the RAM modules as to verify that they are correctly assembled in their respective sockets)
As to double check that the operating system is correctly displaying the available memory, I suggest that you load the task manager from the task bar’s right-click option and click Start Task Manager. From the task manager, which I find more reliable, click the performance tab and view the Total amount of available RAM under the Physical Memory (MB) section.
The first step to check the RAM is to run a diagnostic test from the operating system by typing memory from the Search text box of the Start menu and click the Windows Memory Diagnostic link. This test requires a reboot to run. Other memory diagnostics tools exist but I find this test quite reliable and has detected quite a number of faults for me. However, it did not find any errors in this particular case! This is why I mentioned that RAM problems are quite hard to identify sometimes!
The next step that I suggest is to verify the Memory Channel Timing controls from the CMOS setup. To access the CMOS setup (BIOS) press the Delete key during boot-up when your Gigabyte system shows the fancy Logo screen or Post screen if the logo appearance is disabled. From the MB Intelligent Tweaker (M.I.T) menu option, you can see the timing values of your modules.
A word of caution: Incorrect voltage settings may damage the modules, so modify these settings only if you know exactly what you are doing, and have knowledge about every parameter.
In the following image, notice that the values of Channel A were manually set as this particular module had its values different from the rest! This indicates that this module may be faulty! The fastest way to verify this is by swapping this module with another one and check that the different values swap with the suspected module. Ideally, you would replace the suspected module with a new one but this would be impossible if you have no extra modules at hand when performing such tests!
In addition, I recommend that you check that your motherboard has the latest firmware installed. Pay attention when using Gigabyte’s @BIOS utility that runs from within Windows as I encountered some serious problems on one occasion. I had to download the latest firmware revision and update my motherboard bios manually with a pen drive.