P55-UD3L - Memory Issue

Okay, so first off let me say that I did read the GIGABYTE guide, and I found it very useful. But most of what it suggested I have already tried. My problem has actually been on-going since I first got the motherboard (GIGABYTE-P55-UD3L, rev 1.0), and GIGABYTE tech support had given me such a runaround that I gave up for the time being (that was a few months ago).

The issue I'm having is that my motherboard won't recognize all the RAM. I will go ahead and say that I have thoroughly "memtested" all the sticks using the boot-up disc. Even ran a 5-hour-long depth test. A few months ago, when I got the board, I started off with 4GB DDR3 1600MHz (2x2GB)...got it stable enough to make me satisfied for the moment. But I knew that once I added 2 more modules, problems would pop up. And that's exactly what happened.

I purchased two identical 4GB (2 x 2GB) dual-channel kits since I have 4 DIMMs - G.SKILL DDR3-1600 PC3-12800 (F3-12800CL9D-4GBNQ)
My motherboard is as mentioned - GIGABYTE-P55-UD3L, rev 1.0 and my processor is an Intel Core i5-750
BIOS revision - F7 (latest)
Other specs - APOWER 750w PSU and ATI HD Radeon 5830 GPU

When I installed all the sticks, I booted up into windows and got the "8GB (3.99 usable)" message in the computer properties.
BIOS stated that 4096MB was installed.

I immediately attacked Google for information and have since tried things like resetting the CMOS, searching for bent pins and reseating the CPU (none found), rearranging the RAM modules etc. Typically, I have CPU overclocked to 2.72GHz or 3GHz and RAM to 1500MHz or 1600MHz, but for my troubleshooting I tried both variations of overclocked and default settings. So I think it's safe to say that I've tried just about everything. I've heard others say to enable/disable "memory mapping," but as far as I know that option is not available on this motherboard.

After awhile I suspected it was either a defective slot (which was my prediction several months ago, when GIGABYTE assumed it was my RAM) or the stick itself. I proceeded to install and test each stick one by one in the first slot, then proceeded to fill up subsequent slots. The results surprised me--

I finally managed to get 6GB to show up by filling the first three slots farthest from the CPU (DDR3_3, DDR3_4, and DDR3_1). I thought that DDR3_2 was defective but then I was able to fill DDR3_3, DDR3_1, and DDR3_2, leaving the stick out of DDR3_4. This indicates that Channel B (DDR3_4 and DDR3_2) must have some sort of issue. I can put whatever sticks I want in Channel A (DDR3_3 and DDR3_1) without any problemos. And like I said, I can put one module in Channel B, but when I put both together then the Channel B RAM doesn't show up at all. If I fill Channel B only and put nothing in Channel A, then the computer won't POST and has boot-loops.

Some guidance on how to resolve this issue would be helpful.

Thanks!
5 answers Last reply
More about ud3l memory issue
  1. Channel B may not work as you may need to full up channel A full of RAM before channel B. This is strange.

    Try going to msconfig, the 'Boot' tab, then 'Advanced', and there check the box 'Maximum memory' and type in 6144.
  2. The RAM parameters in both the SPD and XMP on the DIMMs are designed for use in one DIMM per channel situations; for use with two DIMMs per channel, some changes to the RAM setup are usually required: you need to 'bump' your Vdimm a couple hundreths of a volt, you need to bump your QPI/Vtt to within a max of a half volt of your Vdimm (and I like to keep the difference around .35V, just to be sure), you need to raise your tRFC timing 10-15% higher than it's currently at, and you need to make sure that the 'command rate' is set to '2', '2T', or '2N' - whichever way your board shows it...
  3. Lmeow said:
    Channel B may not work as you may need to full up channel A full of RAM before channel B. This is strange.

    Try going to msconfig, the 'Boot' tab, then 'Advanced', and there check the box 'Maximum memory' and type in 6144.

    I only have four slots, two for each channel. Currently, when I fill all four slots with 2GB each, only 4GB total shows up. If I fill three out of the four slots, 6GB shows up. I have already checked the boot tab on msconfig, and the box is not checked, but I will see if I can type in 8GB (8192) to get the full 8GB to show up.
  4. bilbat said:
    The RAM parameters in both the SPD and XMP on the DIMMs are designed for use in one DIMM per channel situations; for use with two DIMMs per channel, some changes to the RAM setup are usually required: you need to 'bump' your Vdimm a couple hundreths of a volt, you need to bump your QPI/Vtt to within a max of a half volt of your Vdimm (and I like to keep the difference around .35V, just to be sure), you need to raise your tRFC timing 10-15% higher than it's currently at, and you need to make sure that the 'command rate' is set to '2', '2T', or '2N' - whichever way your board shows it...

    I've already tried messing with the voltages and it didn't work, but I will follow your suggestions right now.
  5. Okay, I tried everything yall suggested but nothing worked. Guess my next step is RMA. Thanks anyway
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