AM3 CPU on AM2+ board - DDR2 1066 restriction?

I

IronChefMorimoto

Limp Gawd
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Apr 14, 2002
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I'm looking at the following components for an update to my existing Socket 754 rig (yeah -- I've stretched the mileage):

  • Asus M4N78-EM or Gigabyte GA-MA78GPM-UD2H
  • AMD Phenom II X3 720 BE
  • 2GB x 2 Corsair DDR2 1066
  • Western Digital 500GB SATA2 Black HD

When I look through the approved memory lists and manuals for either of the two mobos, I notice that there seem to be a restriction on the number of DDR2 1066 modules you can use on an AM2+ CPU or the motherboard itself. The warning isn't very clear.

My question is -- if I drop an AM3 CPU into either of those boards, will I be able to fill all 4 DDR2 slots with 1066 RAM and get dual channel performance? Right now, I'm only using 2 of the slots in my build, but I'd be interested in getting another 2 sticks for a total of 8GB of DDR2 1066 shortly after the build.

Is an AM3 CPU on either of the motherboards going to bypass that restriction? Or is it inherent to the mobo/chipset itself?

Thanks,
IronChefMorimoto
 
Well when you get all the memory slots filled the memory down clocks on its own to remain stable. Nothing some overclockings to the standard speed, and extra voltage won't fix though. You will still get dual channel performance as well. Last I knew it was more of a motherboard limitation then a CPU limitation too.
 
its a motherboard/cpu limitation xbanzai89..but was fixed the phenom II's.. so it all depends on if the board manufactures updated their bios to correctly support all 4 slots being filled..

ironchefmorimoto.. what do you plan to use this system for? because in my opinion there are a lot better motherboards then those two.. but it depends on what you plan to use the system for..
 
sirmonkey1985 said:
ironchefmorimoto.. what do you plan to use this system for? because in my opinion there are a lot better motherboards then those two.. but it depends on what you plan to use the system for..
Click to expand...

I'm planning on using it as a middle range microATX gaming machine. Mostly Steam games and EVE Online. I spend most of my computer budget on Mac hardware/software for work, so I don't have $800 to drop on a new build. Hence why I'm sitting with a Socket 754 PCI-E motherboard setup now. ;)

I selected these two brands because, of the available microATX DDR2 / AM3 CPU boards available, I was most familiar with the brand. I currently run an ASUS Socket 754 board and have been happy with it, for the most part.

IronChefMorimoto
 
for the most part.. things have changed a lot since the socket 754 and that goes with asus as well.. they are still pretty good.. but some boards are hit and miss from them..

but if its the microatx limitation ya have then both boards are good.. i personally like the 790GX chipset a lot more then the 780g but there are no problems with it just that the 790gx is better.. but theres arent any real choices for a matx 790gx board that stand oh quality wise..
 
Given that I can save $20 (without having to do rebates) on DDR2 800 anyway, would it make more sense to just buy 2GB x 2 of DDR2 800 and then get 4GB more later on and let it run at the native dual channel speed on the board?

Also -- between the two motherboards that I mentioned, would you have a preference? I'm not wedded to ASUS -- in fact, I was tempted to try something new. Gigabyte seems to be a good second choice these days.

Wish the DFI straight up microATX DDR3 / AM3 board was better reviewed, though. :(

IronChefMorimoto
 
Poor selection in the mATX field has been discussed many times here. DFI was the most respected manufacturer to release one for the 790GX AM2+ and I guess now the AM3 as well. I don't know if you can/want to wait or not but there are more options on the way. I know Biostar has a new 780G refresh that supports the full AM3 CPU line:
http://www.biostar.com.tw/app/en-us/t-series/introduction.php?S_ID=415
...but that isn't even on the shelves yet in China so it may be a couple months before it reaches NA.

There is also the new 785G chipset arriving in Q3 this year which should bring with it more options for the mATX gamer:
http://www.hexus.net/content/item.php?item=18665
That is just an AM3 design for example but there might be AM2+ as well, or one of the AM3/DDR2 hybrids (which is essentially the same thing:p).
 
I would say that you won't notice a difference either way especially in gaming. It also depends on if you would ever really want to buy 4 mor GB later on. Or if you are going to be OC'ing your machine and if it is a BE CPU or not.
 
I ended up selecting the DDR2 1066 (4GB total) and the Gigabyte motherboard. Looking forward to finally upgrading from Socket 754. Just wish the CPU wasn't shipping from CA -- I'll be looking at all my parts this weekend waiting for Monday's delivery. ;)

Thanks for the input -- it was all very helpful. Will be looking here again when I finally decide to ante up for DDR3 and a true AM3 motherboard.

Regards,
IronChefMorimoto
 
CPU? Huh. Which?
If you did it right this time, I don't see you wanting a DDR3 and AM3 board any time soon/ever. You waited this long to upgrade from a socket 754, can't see you upgrading again for 3-5% improvement.
 
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