AMD AM2: More than just a Memory Change

The new AMD technology refresh, now called AM2, will bring DDR2 memory to the Athlon64 on-processor memory controller. Many in the industry have speculated about the impact of this low latency memory controller on DDR2 performance, which to this point has suffered under the impact of the higher latency Intel Netburst architecture. We are looking forward to the opportunity to take a closer look at DDR2 performance on AM2 - which is everyone's big question.

There will be more than just new memory with AM2, however. We now have details on the new Socket 940 for AM2. It has been widely reported that the new Socket 940 will not be compatible with the existing Socket 940 used for Opteron and early Athlon 64.

Photos of the back of the new AM2 processor show how very close the new design is to the current Socket 940.

AM2 Processor

Current Socket 940 (Reversed)

By flipping the current 940 socket photo and comparing pin-outs to the back of the AM2, you can clearly see the top 2 "lands", areas without pins, are identical in the current Socket 940 and the AM2 Socket 940. However, the bottom two lands are in different locations. The bottom right land is the same 2 pins up, but 7pins form the edge instead of the 5 in the current 940 design. The left land is also in the same row position as the current 940, but it is 6 pins from the left edge instead of 8 as in the current 940 design.

The AM2 940 and current Opteron 940 are so close in design; you have to conclude that AMD could have used the same socket design. But there are numerous electrical differences and different memory is required. AMD apparently used a revised Socket 940 to prevent any possibility that AM2 chips might get accidentally mounted in current Socket 940 motherboards. That is probably a very wise decision.

New AM2 Cage
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  • xsilver - Monday, February 6, 2006 - link

    i think what one dude was reffering to above was it would be great if amd made a socket that was obviously different -- having 2 socket 940's that are not compatible may lead users to jam an old socket 940 cpu into a am2 mobo and bend the pins
  • mesyn191 - Monday, February 6, 2006 - link

    I doubt that'll ever happen as outside of the server market socket 940 chips are unusual, socket AM2 is for consumers... Also the raised portions on the socket itself should prevent the chip from even laying flat in the first place, there isn't any way anyone with half a brain to screw it up as they'd have to use a hammer to flatten it out and even an idiot would know you don't use a hammer to install a CPU LOL.
  • tygrus - Monday, February 6, 2006 - link

    If the northbridge had a DDR memory contoller built in, then the CPU could reuse the old stuff as additional RAM (slower + more latency) or the OS use it as a RAMdrive.
  • mesyn191 - Monday, February 6, 2006 - link

    No, they'd have to put 2 memory controllers on there in order to be able to use DDR and DRR2 with the same chip, they'd probably also have to add several hundred more pins to the package to greatly increasing costs... You're also forgetting increased motherboard costs as you'd need 2 different sets of RAM slots on the motherboard which would be difficult to route properly that close to the CPU, you'd probably need 8 layers or more just like on a server motherboard and those cost a bundle.

    Its a silly, pointless idea anywhich way you look at it as even if you could make it cost effective you'd only be able to have a 8GB RAM drive (assuming 4 DDR RAM slots) max, which is much to small to be worth anything, not to mention the cost of 2GB DDR DIMMs which even at PC2100 speeds cost $156 a piece. What a waste of money...
  • eastvillager - Monday, February 6, 2006 - link

    ...which is a pretty good sign they shouldn't be working inside a pc.

    If people don't understand the ZIF concept, they need to leave CPU installation to somebody who does.
  • chennhui - Monday, February 6, 2006 - link

    Hi Wesley Fink,

    Could you pls label your pictures/figure? It look a little bit confusing. Thanks.

  • Wesley Fink - Monday, February 6, 2006 - link

    Labels were added to the side-by-side comparisons.
  • SnoMunke - Monday, February 6, 2006 - link


    those moving to AM2 will at a minimum need a new processor for a new Socket 940, new DDR2 memory to replace existing DDR memory for Athlon 64, and a new or revised heatsink/fan cooling solution.

    Since the "new Socket 940" will basically mean a new motherboard, doesn't this pretty much sum up to "a whole new computer"?
  • Olaf van der Spek - Monday, February 6, 2006 - link

    No. Existing F/H/ODD, PCI(-E) cards, case and PSU can be used.
  • huges84 - Monday, February 6, 2006 - link

    Is it just me, or are socket 940 and socket AM2 too similar? I don't think that the differences are obvious enough. It would be pretty easy to mistake one for the other. Also, I don't understand the change in heatsink mounts, unless the cooling rewuirements have changed enough that previous coolers are inadequate. Maybe they are trying to encourage OEMs to buy their heatsinks from AMD instead of making their own? I hope the new heatsinks will at least still use the locking lever design. That was pretty simple and worked well.

    I was hoping for a lot more information when I saw the article. I thought maybe AMD was ahead of schedule and so we were going to get some details early. But the article says they're a little behind. Oh well. At least the delay 'til summer will coincide with me getting the money to upgrade. Of course I need to see a few reviews first.

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