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Cannot use 4 memory slots for dual channel...

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August 26, 2011 2:41:46 AM

Just finished first build, I'm trying to use all four memory slots for my Gigabyte GA-990FXA-UD3 AM3+ motherboard. Basically, the memory works well when I put it in the first two slots and the last two slots (CPU-ID detects all 8 GB), so the slots and memory are at least working. However, when I try all four slots of the below memory, the system won't boot (with 16GB of memory total), only black screen. Yes, I know this is overkill with 16 GB, but all the sticks work as pairs of two, but they won't work as a set to take advantage of dual channel. My memory is CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ8GX3M2A1600C9B. Any suggestions? BIOS problem? Anyone have a similar problem with the new AM3+ mobo's? I really appreciate the help.

CPU: AMD Phenom X2 555 BE
Coolermaster 700 W PSU
Gigabyte GA-990FXA-UD3 AM3+ Motherboard
nVidia EVGA GTX560ti
Corsair Vengeance 8 GB (2x4GB) (for now)
1.5TB Western Digital HDD
a b } Memory
August 26, 2011 2:53:56 AM

check in your bios for memory detection could be just bios setting to made
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a b } Memory
August 26, 2011 3:01:50 AM

Not all memory works with all CPUs/Mobos. If the RAM you have is specifically designed for AMD Phenom II CPUs and the model Gigabyte mobo you have, then you should contact Gigabyte about a BIOS update.

If you did NOT purchase the Corsair memory as a MATCHED SET of 4 x 4Gb. DIMMS, it may not work. Purchasing TWO SETS of 2 x 4 Gb. is NOT guaranteed to work. Corsair has a Tech Note on memory upgrade on their website explaining this.
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August 26, 2011 5:44:56 AM

nforste said:
Just finished first build, I'm trying to use all four memory slots for my Gigabyte GA-990FXA-UD3 AM3+ motherboard. Basically, the memory works well when I put it in the first two slots and the last two slots (CPU-ID detects all 8 GB), so the slots and memory are at least working. However, when I try all four slots of the below memory, the system won't boot (with 16GB of memory total), only black screen. Yes, I know this is overkill with 16 GB, but all the sticks work as pairs of two, but they won't work as a set to take advantage of dual channel. My memory is CORSAIR Vengeance 8GB (2 x 4GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) Desktop Memory Model CMZ8GX3M2A1600C9B. Any suggestions? BIOS problem? Anyone have a similar problem with the new AM3+ mobo's? I really appreciate the help.

CPU: AMD Phenom X2 555 BE
Coolermaster 700 W PSU
Gigabyte GA-990FXA-UD3 AM3+ Motherboard
nVidia EVGA GTX560ti
Corsair Vengeance 8 GB (2x4GB) (for now)
1.5TB Western Digital HDD


Doesn't the Phenom II memory controller have issues with 4 DIMMS at 1600? Try turning the memory speed down and see what happens.
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a b } Memory
August 26, 2011 4:49:57 PM

FALC0N said:
Doesn't the Phenom II memory controller have issues with 4 DIMMS at 1600? Try turning the memory speed down and see what happens.

It is likely this. It's unfortunate, but controlling four DIMMs at high speed is much more difficult than controlling two DIMMs at that same speed. And AMD's memory controllers were never the strongest to begin with. I suggest you boot with two DIMMs, manually change the memory speed to 1333, save and exit, shut down and install the third and fourth DIMMs. You may also need to increase the RAM voltage slightly in the BIOS, as some boards need more voltage to handle four DIMMs.

It could also be what beenthere suggested, but that is less likely.
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September 3, 2011 9:08:39 PM

Thanks for all your help, guys, but it still isn't working. I tried lowering the Memory Clock in BIOS and upping the voltage slightly, it still wouldn't boot. I currently reset it to defaults and I am wondering what I should try next. I should have the memory set in the first two slots closest to the CPU heatsink, correct? So the new memory would go in the next two slots (two slots farthest from the CPU heatsink). Thanks for the help, guys, any other suggestions would be appreciated.
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December 6, 2013 3:17:51 PM

I have the same board, and a similar situation. I've read that the Phenom II chips don't have the same memory controller as the AMD FX chips. I'm pretty sure you can only run 2 sticks of ram with the Phenom II CPU, and they won't run any faster than 1600. I was running a Phenom II 965 and I just upgraded to a AMD FX 6350, my RAM immediately bumped up to the XMP 1866 speed.

For the record, I'm running G.Skill 1866 Snipers 2x 8gig.
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