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GA-EP45-UD3P - Dual channel memory not working with 4 DIMMs?

Hello. I have a GA-EP45-UD3P motherboard and have been using Corsair DDR2 800 (PC26400) 2 x 2GB in slots 2 and 4 for several years. I believe it had been operating at 800 MHz during that time. I recently added another 2 x 2GB of the same memory and inserted those into slots 1 and 3. This fills all 4 slots and brings the total RAM to 8GB. The computer boots and operates normally, but now the RAM is only running at 400 MHz although in the BIOS it's shown at 800. I used Speccy and CPU-Z to check the speed. I was wondering if I'm doing something wrong, or if the board is somehow not capable of running 4 modules in dual channel mode. I updated the BIOS to the latest version and it didn't make a difference. I haven't altered any of the default CPU or RAM settings in the BIOS. The CPU is an Intel e8400. Can anyone help me? I'll provide any further info that's relevant.

This is the RAM: The second pair I bought are called TWIN2X4096-6400C5C, I believe the extra C on the end stands for Classic.

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  1. Best answer
    The RAM is running at 800 MHz. DDR2 runs at twice the clock speed; therefore 400 x 2 = 800.
  2. I do not know about Speccy, but CPU-Z reports the memory frequency, not the memory clock which is twice as high as the frequency in a DDR2 system.
  3. I didn't realize that. I just looked on Google about how to confirm dual channel and it turns out it said all along in CPU-Z that it was dual channel at the top of the memory tab. Thanks for clearing that up.
  4. I have a followup question. I just discovered that one of my DIMMs was showing errors under Memtest86. I took it out, leaving the other three modules in, and assumed that my PC would boot into single channel mode. In Memtest, CPU-Z, and Speccy it's telling me that it's still in dual channel symmetric mode. Is this even possible? I thought you needed even pairs of RAM to get dual.
  5. Two modules run in dual channel mode and one runs in single channel mode.
  6. Best answer selected by Chong Li.
  7. This topic has been closed by Maziar
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