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Athlon II Memory Speed Limitations.

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October 3, 2010 6:49:24 PM

Hello,
I have an Athlon II 630 processor running with some DDR3 1600 memory. I've read numerous postings around the net alluding to the fact that AMD Athlon II CPU's cannot run with DDR3 memory over 1333, and that the board will automatically underclock the memory if it is set any higher. Is this accurate, is there no reason to set the memory to anything above 1333 for Athlon IIs.
a c 346 } Memory
a c 715 V Motherboard
October 3, 2010 6:56:07 PM

Welcome Newcomer! :) 

Please post your MOBO model and your RAM part-Number. I am pretty good about reading manuals and ignore posts/Googl'ing.

Most MOBO's will not automatically detect 1600 MHz DDR and you will need to make some BIOS adjustments.

Examples:
ASUS M4A88T-M {supports you CPU}
4 x DIMM, Max. 16 GB, DDR3 1866(O.C.)/1333/1066 ECC,Non-ECC,Un-buffered Memory

ASUS M4A79XTD EVO {supports you CPU}
4 x DIMM, Max. 16 GB, DDR3 1800(O.C.)/1600/1333/1066 ECC,Non-ECC,Un-buffered Memory
October 5, 2010 1:19:06 AM

GA-MA790GPT-UD3H
4 x 1.5V DDR3 DIMM Support for DDR3 1666(O.C.)/1333/1066 MHz memory modules

A-DATA Gaming Series 4GB (2 x 2GB) 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800) AX3U1600GB2G9-2G


AMD's Athlon II website:

Type of Memory Supported :X3 and X4 - Support for unregistered DIMMs up to PC2-8500 (DDR2-1066MHz) -AND- PC3 10600 (DDR3-1333MHz)

http://www.amd.com/us/products/desktop/processors/athlo...

AMD says that higher frequencies of RAM are not supported, but I can set mine to 1600 with no problem. CPU-Z even says its running at 800mhz.
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a c 346 } Memory
a c 715 V Motherboard
October 5, 2010 3:54:11 AM

Don't confuse Memory Controller speed with Memory speed; it doesn't take into account multipliers. i7 has a 1066 MHz but the Memory speed is a multiplier of BCLK X Memory Multiplier; others use FSB multiplier but the principle is essentially the same; similar to CPU multipliers - imagine a CPU with (1); 1 X BCLK will be pretty slow.

Note pg 16 manual DDR placement.
MB Intelligent Tweaker(M.I.T.)

Set Memory Clock {Auto} -> {Manual}

Memory Clock = 1600 / CPU Frequency {e.g. if CPU Freq = 200; 1600/200 = 8}
Next, manually set all of the CAS Timings

Save & Exit.

This link will help - http://en.wikipedia.org/wiki/Memory_divider
October 12, 2010 2:53:17 AM

Actually this forum post seems to answer my question:

http://www.tomshardware.com/forum/286524-28-speed-limit...

One of the responders writes:

"the max memory speed is from the memory controller which right now for both Intel and AMD is inside the cpu, and i would imagine that loneninja is probably right about why

though from what it seems most of these memory controllers are fine and can run at much higher speeds than they are rated, thoguh it is possible to get one that can only run at the advertised speed "

Another writes:

"Ram speed has nothing to do with CPU speed at all. Both can be under/overclocked independently. For example with Intel systems, both have their own multipliers, linking them to one general clock, namely the FSB for older systems or the Baseclock for i-x systems.

To conclude, you can run any ram on any cpu, however you'll have to make sure your mobo supports both speed and type of ram. To do that, read reviews. You won't have to OC the CPU to be able to clock the ram at higher speed, unless there's some kind of technical limit, like not having a high enough ram MP, to get the desired ram speed at the current general clock, however that's not likely. Even then you can still up the general clock and lower the cpu mp to keep it at the same speed."

That answers my question, thanks for all the info.
!