AM2+ CPU Limitation with DDR2 1066 Explained - Overclock.net

Cavi · 04-22-09

I thought I would post this because there seemed to be some confusion on the exact limitation involving AM2+ CPUs and DDR2 1066 ram.

Quote:

Due to AMD CPU limitation, DDR2 1066 memory module is supported by AM2+ CPU for one DIMM per channel only. Please keep this limitation in mind when you purchase your DDR2 1066 memory module.

Source

Essentially what this means, is as long as you are only running 2 DIMMS in Dual Channel, you will be perfectly fine (example, a 2x2gb pair).

Any setups involving more than 2 DIMMs (ie., 3x2gb or 4x2gb, 4x1gb... and so on) will give you problems. You can try underclocking your RAM, but you might as well buy DDR2 800 RAM with tighter timings

Just thought some members would benefit from this info!

denrocks2 · 04-22-09

You can overclock to 1066mhz and it would be fine.....

wraeththu · 04-22-09

Good Post.

I dont own an AM3 Mobo but ive read from a few different resources that the same is applied to DDR3. Go over 2 DIMMs and things get nasty.

Cavi · 04-28-09

Yeah I just see so many people posting with problems and/or asking about it

breakfromyou · 04-29-09

If i got another DDR2-1100 4gb kit, would i be able to pair it up with my Phenom II 720? I'd like it to actually run at 1100, is this too much to ask for?

Gill.. · 04-29-09

My 4 DIMMS at 1066 is a no-go, so it's only stable at 800. Had I known that originally, I'd have opted for the 800.

But, now that my 940 arrived at lunch - I'm thinking of taking 2 DIMMS out and opting for the 1066.

Da5id · 04-29-09

Quote:

Originally Posted by Gill..

My 4 DIMMS at 1066 is a no-go, so it's only stable at 800. Had I known that originally, I'd have opted for the 800.

But, now that my 940 arrived at lunch - I'm thinking of taking 2 DIMMS out and opting for the 1066.

Dont stress too much on bandwidth since theyre relatively close, just try and get the tightest timings possible out of them(them being 2x 2gb).

GL

logan · 04-29-09

Quote:

Originally Posted by breakfromyou

If i got another DDR2-1100 4gb kit, would i be able to pair it up with my Phenom II 720? I'd like it to actually run at 1100, is this too much to ask for?

unfortunately, that probably wont work out so well. In order to get things working, you would have to lower the speed on the ram.

This is all because of the IMC btw. The IMC is a great design, and is a huge improvement over the old fsb based designs, but when enough stress is placed on the IMC (through lots of dimms that are trying to be OC'd), it has a tendency to become unstable. Most OC'ers have known for a while that OCin with all 4 dimms full leads to lower stable ram OC's.

However, I would just like to point out that the difference between fast and slow ram with the same timings is fairly insignificant (less than a 5% difference in total system speed for sure)... that this isn't to big of a deal in the grand scheme of things.

Great post though, for a large majority of people, this is not common knowledge. + rep

Cavi · 05-05-09

Quote:

Originally Posted by logan

unfortunately, that probably wont work out so well. In order to get things working, you would have to lower the speed on the ram.

This is all because of the IMC btw. The IMC is a great design, and is a huge improvement over the old fsb based designs, but when enough stress is placed on the IMC (through lots of dimms that are trying to be OC'd), it has a tendency to become unstable. Most OC'ers have known for a while that OCin with all 4 dimms full leads to lower stable ram OC's.

However, I would just like to point out that the difference between fast and slow ram with the same timings is fairly insignificant (less than a 5% difference in total system speed for sure)... that this isn't to big of a deal in the grand scheme of things.

Great post though, for a large majority of people, this is not common knowledge. + rep

Thanks! Although I am posting in the technically correct spot, I'm starting to think that I posted this in the wrong forum, as no one checks here. More people actually frequent the AMD Motherboard forum...

Thanks for your addition! Very good info...

laurie · 05-09-09

May I ask what issues this causes?
I have been running my 940 at 3.5 with my 4 1gig 1066 modules in an Asus Crosshair 1 without any problems. I would like to understand better what the issue is here.
Thanks.

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AM2+ CPU Limitation with DDR2 1066 Explained

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