M2N-VM HDMI DRAM speed?????

akshye · Posted: Tue Jun 24, 2008 6:16 am Post subject: M2N-VM HDMI DRAM speed?????

Hi all,
I have got ASUS's M2N-VM HDMI motherboard, Transcend 800MHz 1GB x 2 DDR2 RAM and Athlon64 X2 5600+ AM2 socket processor.

The problem is in the manual of the motherboard company has mensioned memory speed support of upto 1066MHz (not all processors are supported!) but 800MHz for all processors. Now even though I have installed 800MHz RAM, I don't find any option in BIOS of 800MHz for memory? Even I don't know how to overclock the system(as one can see this won't be actual overclocking if I try to run the RAM at 800MHz Wink

) to get the desired RAM speed.

Can anyone help me out to configure BIOS of this motherboard to run the RAM at specified speed(800MHz)?

Thanks in advance.

cp · Posted: Tue Jun 24, 2008 7:27 am Post subject:

read this: (actually READ this)
http://icrontic.com/articles/a64_overclocking_theory

the memory controller is inside the cpu. the memory clock is calculated from the cpu clock or the reference clock. the reference clock is 200MHz for all (not quite sure) A64 and is generated by the motherboard. if the memory clock is derived from the cpu clock, the cpu has divisors that can be controlled by the motherboard by writing some cpu registers. your ram can be operated at max. 400MHz (marketing people tend to multiply the clock by 2 when they sell DoubleDataRate RAM, but that's utter nonsense). if you select 400MHz or DDR800 in the bios, the divisor will be (cpu clock/ram clock) = 2800MHz/400MHz = 7. if you select DDR667, the divisor will be 2800MHz/333MHz ~= 8.4 = 9 (only integer values are allowed)

the article referenced by the link also tells you how to overclock, so i won't go into it. you can do the math yourself now :)
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akshye · Posted: Wed Jun 25, 2008 10:25 am Post subject:

Thanks for your quick reply and for sending me so helpful link.

I have currently set my memory speed as AUTO. Can you tell me exactly how can I find at what is the speed it is currently running? and should I make the memory speed as 400?

As you have mensioned here if speed set is 400, for DDR it becomes 800. But as my motherboard manual notes that the max speed supported is 1066 and still there is an option 667MHz which with this calculation turns out to be 1333, which is outside the limit?????

Thanks again.

cp · Posted: Wed Jun 25, 2008 4:30 pm Post subject:

Maybe for future revisions of AMD processors? as i already stated : the memory controller is inside the cpu and so is its divider. upto today all AMD cpus are rated 400MHz when it comes to their max. memory controller frequency thus making its divider the lowest available.

or to say it even shorter: you can not have a higher memory clock than the default with the stock cpu core clock.
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Denniss · Posted: Wed Jun 25, 2008 5:51 pm Post subject:

Run some system utility software like CPU-Z, everest or sandra, they should be able to show you your current memory speed.
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