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CMZ16GX3M4A1600C9 on GA-990FXA-UD3: not running at 1600 MHz

Someone Else

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I just put together a new desktop system from individual components.

Have not installed an OS yet. Just turned on the computer

and went into the BIOS to check if everything was ok.


Memory: Corsair CMZ16GX3M4A1600C9

Mainboard: Gigabyte GA-990FXA-UD3 rev. 1.0 with BIOS version F4.

CPU: AMD FX-4100 @ 3.6 GHz (not overclocked).


The mainboard is specified by the manufacturer

to support up to 1866 MHz without overclocking.

However, my Corsair 16 GB (4 x 4 GB) 1600 MHz DDR3 kit is running

at 1333 MHz instead of at the rated 1600 MHz.

When I went into the BIOS to change the memory clock to 1600 MHz

and rebooted, I got an error message saying that the system

had experienced a "boot failure" due to "overclocked memory",

so I was forced to change it back to 1333 MHz.

I find it strange that the BIOS calls it overclocked even though 1600 MHz

is the rated speed of the RAM.


What do I need to do to make the memory operate at its specified

1600 MHz speed on my system?

I would like to find out what BIOS settings I need to adjust.

Can it be done?

Or am I stuck at 1333 MHz memory speed due to a compatibility issue

between the mainboard and RAM?

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For motherboard u could intall F5 final or F6f beta. Bios help for stability

Try 1 stick in slot 1

Try same stick in slot 2

Repeat with all 4 stick

Do pc start with all 4 stick wend only 1 install in slot 1 or 2?

If not u ave a defective memory stick

Sould worck as Support for DDR3 2000(O.C.)/1866/1600/1333/1066 MHz memory modules

If it start with 1 or 2 stick but not with 4, maybe u ave to tweak voltage for OC to be stable.


Hope this help

Sincerly yours

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Hey there Someone else.

there is nothing wrong with your ram, motherboard, or your settings that you have applied.

It is a long standing problem with AMD CPU's and it has happened ever since the single core amd 64's were released. and the issue is .

that the memory controller can not run at max speed with fully populated ram.

in the old single core days, they couldn't even run in dual channel! they would revert to single channel as the control would not handle the load. so in that sense it has improved a little. true story I made AMD send me a revised chip when the AMD 4000+ was the best CPU out, it cost me a fortune I think it was almost 1000 dollars back then.

and so I did the same thing bought the best ram, and the same thing happened, so I called AMD and spoke to their engineer, who was aware of the problem, but I explained it was false advertisment as the box said dual channel ddr 400. so he sent me a engineering sample of the revised stepping of the 4000 and let me keep the old chip !!, that was a good day for me .... haha


There is a few reasons I don't want you to worry about this. and I understand you are going to be frustrated after what I have said, so here goes.

I know you bought 1600C9 sticks so you could have fast memory, so I get that

but what you also need to know is AMD's memory scaling doesn't respond too well to Raw speed anyway. meaning the AMD on Die memory controller runs at 1333 mhz. So running it any faster is pretty much useless. sure you may get a little speed. but you are essentially making a bottleneck.

However What AMD CPU'S respond really well to, is matching their memory controller speed. So 1333 mhz, and getting the tightest timings possible.

I have the exact same board, I run a phenom II 955 tho. and I have 2x4 gb sticks of the same ram.

I can run 1600 because I have only 2 sticks, but its not any faster then 1333 setting.

what is faster is and I run it like this!

under clocking the ram to 1333 to match the ram to the memory controller speed. and adjusting the timings to

7-7-7-20 1T @ 1.6V and the speed is very good. the response is amazing, and you will be happy.

what you also get is extended life of your ram, because you are under clocking it, and it wont be running on the edge of stability :)

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@jjbk: many thanks for your interesting reply.

I learned something new.

I had the option of buying 2 x 8 GB RAM to get 16 GB,

but it was more expensive than 4 x 4 GB, and since I can

not imagine I will ever need to upgrade to 32 GB RAM,

the cheaper 4 x 4 solution seemed more logical.


I read some posts by other forum members who managed to

force their 4 x 4 GB RAM kits to run at 1600 MHz but they reported

experiencing instability and crashes. For me stability is more important

than performance, so I will do as you recommended and just leave my system

at the 1333 MHz memory speed that the BIOS has selected.


I actually looked at some benchmarks where the influence of different

memory speeds were compared and there was no difference.

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cool im glad you understand.

also did you adjust the timings?

so run them at 1333mhz, and change the timings that are mostlikely his at the moment

9-9-9-24 2T and change them to

7-7-7-20 2T and adjust the voltage to 1.55V it will make it much mre responsive, an d you arent overclocking it , you are still runnin it much slower then its intended speed of 1600mhz :)

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everytime I've changed anything from auto to manual memory wise in an AMD rig it made my gflops in linx go to ****. like 15-20% drop in gflops while stress testing an overclock. even ram thats running 1333 9 9 9 24 by default, then manually setting the exact settings it does auto (only changing manually 1333 and timing to 9 9 9 24) dropped gflops to low 40s on 4.1ghz 955be. all other settings were the same and with ram on auto gflops were well into the 50s. may have been a defect in the exact board I was using. I've said it before and I'll say it again, if you're a gamer you wont see a difference between 1333 9 9 9 24 and 2000 9 9 9 24. Even if you do more than game, might save you a few minutes over a year in video editing.
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