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I have an ASUS P5QC MB and one of my old Cosair DDR2 sticks recently failed on me, so I decided to get new memory sticks. Since my motherboard is capable of accepting both DDR2 (4 slots, 16 GB max) and DDR3 memory (2 slots, 8 GB max), I decided to buy some Kingston DDR3-1333 8GB memory.

After replacing the sticks, I tried turning on my computer, only to find a blank screen, but everything else still running (fans running, HDD ok, etc). I ran a few tests both with the hardware and BIOS and listed the results below:

  • Booted computer with one stick of DDR2: Normal boot
  • Booted computer with one stick DDR3: computer running, but no monitor
  • Cleared CMOS and booted with DDR3 RAM: same issue
  • Cleared CMOS and booted with DDR2 stick: Normal boot
  • Removed all RAM and turned on computer: computer running, but no monitor

It was with the last test that I realized that I did not have a system warning speaker plugged in...but from what I have tested, my impression is that my MB is not recognizing the DDR3 RAM, despite having slots for it. Givent his, my question is whether I should just return the DDR3 RAM and just buy some DDR2 or if there is a way to get my computer running with the Kingston memory.

Thank you in advance.

PS: I am unsure if this matter too much, but my CPU is intel core 2 quad.

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What kind of memory modules are used on the DIMMs? The manual for your system states you can't use memory modules made up of 128 Mb chips, and I'm going to guess that actually means 128 Mb or larger . . . – ernie Sep 10 '13 at 20:33
They indeed mean 128 megabit per chip or larger. (With a DIMM usually having 4 or 8 chips per side). – Hennes Sep 10 '13 at 20:37
If it helps, here is the DDR2 and DDR3 RAM specs:<>; <>; – Umesh Jonnalagadda Sep 10 '13 at 21:07

Could be you have some bad RAM?

Possibly might have to flip a switch/jumper on the motherboard for RAM type?

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I found another thread mentioning something about a jumper in this MB to switch between DDR2 and DDR3...I am unsure where it would be, however, and nothing like that is mentioned in the manual. – Umesh Jonnalagadda Sep 10 '13 at 20:44

As far as I know there are no motherboards at all on the market which allow you to use both DDR1 and DDR2, or DDR2 and DDR3 at the same time.

So check your motherboards manual. You will doubtlessly find that you can use either DDR2 or DDR3. Not both at the same time.

There is not telling what happens if you use both of them at the same time. You could even damage the new RAM (which usually requires lower voltages).

PS: I am unsure if this matter too much, but my CPU is intel core 2 quad

In this case the memory controller is in the chipset, specifically in the northbridge. It is not on-die with the CPU. SO for this motherboard/CPU it does not matter.

What you want to do is:

  • Check if the new RAM works in another desktop.
  • If it does an you want to use it, use ONLY the new DDR3 sticks in the right sockets. This should work, assuming the BIOS is up to date and assuming the DIMMs where not damaged.
  • If you want to use the old ram, return the new DIMMs.

Before you get new DIMMs, read the supported memory list P5QC_QVL.pdf. Notice that list is 2GB (2048MB). That does not mean that larger DIMMs will not work, just that they were not tested. Usually because they were not available at the time the board was produced. And since memory chips change over time newer (and larger, more mbit chips) simply might not work.

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I apologize if I was not clear before, I am using either DDR2 or DDR3 memory in my machine, not both simultaneously. Unfortunately, the is the only desktop in my home, so I cannot check to see if the memory is faulty or not. – Umesh Jonnalagadda Sep 10 '13 at 20:42

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