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8GB of RAM is de-clocked

Mon May 12, 2008 3:03 pm

Hey everyone,

My colleague is building a photography editing rig and would like to use 8GB of DDR2. I recall reading recently (somewhere) that motherboards will de-clock DDR2-800 to DDR2-667 if you use 8GB of RAM.

1) Is this true?

2) Does it happen with just some motherboards/chipsets?

3) Is it specific to AMD or Intel or both?

4) What if he uses DDR2-1066? Will it be de-clocked to 667 as well?

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Re: 8GB of RAM is de-clocked

Mon May 12, 2008 3:37 pm

It is possible that the memory controller will throttle the RAM back for various reasons. My system throttled my DDR-400 down to 200 once I threw in a second pair of DIMMS. Seems that the BIOS didn't have a 2T option to tell my 4000+ that it needs to run with a lower command rate and just clocked everything back to make sure it worked. Once in Windows though, I used a software overclocking utility to force 2T and adjusted the timings to "resupport" 400 MHz. It's a real pain to bring it back up everyday though, so I only do it when playing games. Granted this is a 939 system and a really cheap replacement motherboard so, I'm not sure if this helps. The issue had to do with the number of DIMMs though, rather than the actual amount of RAM.
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Re: 8GB of RAM is de-clocked

Mon May 12, 2008 4:25 pm

This is the first I have heard of it. I wouldn't worry about it though. There isn't a huge noticeable difference between DDR2-667 and DDR2-800. Especially when it comes to photo editing.
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Re: 8GB of RAM is de-clocked

Mon May 12, 2008 4:28 pm

paulsz28 wrote:
1) Is this true?

It could very well be true for certain cases, as I've heard of instances where the motherboard didn't recognize the brand (and picked the lowest timings by default) or just picked the lowest timings by default when 4 sticks of RAM were inserted.

I just finished building a rig with 8GB and had no trouble running the RAM -- high quality I might point out -- at stock speeds.

What you'll need to do is go into the BIOS and make sure the RAM is running at stock, although again, in some cases, you may need to adjust the CAS timings more conservatively for it to work.
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