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Old 09-15-2012, 02:25 AM   #1
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Default Help figuring out RAM type

Hi I need some help figuring out the type of RAM I currently have installed. I have an ASUS M4A88TD-M motherboard, with a AMD Phenom II x6 2.8GHz processor and 12GB of RAM. The RAM is set up as 2 x 2GB DIMMS and 2 x 4GB DIMMS. According to my mobo manual and Crucial's memory scanner, the types of RAM my mobo can support are:

DDR3 PC3-8500 (1066MHz)
DDR3 PC3-10600 (1333MHz)
DDR3 PC3-12800 (1600MHz)
DDR3 PC3-14900 (1866MHz)
DDR3 PC3-17000 (2133MHz)

When I use cpu-z, the Memory tab shows the following info:

Frequency - 562.5MHz
FSB : DRAM - CPU/5
tCL - 9.0 clocks
tRCD - 9 clocks
tRP - 9 clocks
tRAS - 24 clocks
tRC - 34 clocks
CR - 2T

So according to the Wikipedia article on DDR3 SDRAM (DDR3 SDRAM - Wikipedia, the free encyclopedia), based on my RAM timings, I either have PC3-10600 or PC3-12800. But I can't figure out how to translate the RAM frequency to what RAM type I have. Even if I half the frequency (since it's DDR or double data rate), I get 281.25MHz. According to cpu-z my FSB is running at 200.9MHz with a multiplier of x14. But 281.25MHz is nowhere near the memory clock rates listed on the Wiki article. What am I missing? Any help is very much appreciated.

PS. I know I can turn off my computer and open up the cover to check the physical modules. But I want to learn how to check the RAM type when computer is running.

David H.
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Old 09-15-2012, 08:32 AM   #2
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Default Re: Help figuring out RAM type

it works like this.
the PC3 tells you that you are running DDR3. so PC2 is DDR2.
the number after is the speed in megabits (note: i said bit, not byte). so by dividing the megabits by 8, you will get the the speed in mhz.
CPU'z says that your ram are running at 526.5mhz. you need to double that so you get 1053 mhz.
Because your RAM are running at 1053 on stuck which is closest to 1066 (which is 8500 megabits) and your RAM are DDR3, your RAM type is PC3-8500.
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Old 09-15-2012, 09:29 PM   #3
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Default Re: Help figuring out RAM type

Thanks EchoNatek for that explanation. I have a couple of follow-up questions.

Firstly, you wrote
Quote:
the number after is the speed in megabits (note: i said bit, not byte). so by dividing the megabits by 8, you will get the the speed in mhz
. How does dividing a speed in megabits (per second I'm assuming?) by 8 give you the speed in mhz? I'm not following the relationship between data transfer rate and cycles/second.

Secondly why is cpu-z reporting that my ram is running at 1053 MHz instead of 1066?

Thanks again.
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Old 09-16-2012, 07:49 AM   #4
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Default Re: Help figuring out RAM type

i am not an expert on that area but frequency has high and low just like bit has on and off. i found this picture that shows how it works.
you can also google it, you will fine some converters and demonstration on how to convert it. so you will see that it works.


my CPUz shows that my RAM are running at 1686mhz. the RAM module here is PC3-12800.
the reason mine is slightly higher then 1600mhz is due to the motherboards bus speed. mine is 140.5.
my BusSpeed to DRAM ratio is 2:12. so if my bus speed are 140.5 i have to divide it with 2 so i get 70.25. now i can multiple it with 12 so i get 843.
and because 843 is my DDR RAM speed i can multiple is with 2, so i get 1686 mhz.

take this for another example. http://3.bp.blogspot.com/-Rk7x5bZcG5...1600/CPU-Z.jpg
he has a BUS speed at 199.9, and a Bus to Dram ratio at 2:6. now divide 199.9 with 2 and multiple it with 6.
you will get 599.7 (or .8 in this example for some reason) with is the Dram Frequency CPUz shows.... and then multiple it with 2 so you get 1199.4 mhz.

i don't understand why your CPUz says FSB : DRAM - CPU/5.
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