New AM2 Cage

With the two 940 sockets so similar you would reasonably expect existing heatsink/fans to work on the new AM2.

After all AMD has maintained the same "cage" design though 754, 940, and 939 sockets. The same heatsink/fan can be mounted on any of these sockets without concern about compatibility.. Those with large and exotic cooling solutions have other concerns about whether motherboard layout may block their cooling device, but overall there has been one HSF design through all the Athlon 64 socket designs.

Click to enlarge.

It appears AM2 will change this ongoing HSF compatibility with a brand new, and mostly incompatible, heatsink cage design. The new AM2 design, if it makes it to final production, is a nice upgrade to the existing Athlon 64 HSF mounting design, but there are almost no current Athlon 64 HSFs that will fit the new design.

If you look at the designs side-by-side you can see the differences more clearly.

Socket 939/940/754 HSF Cage

AM2 HSF Cage

While the spacing width of the center mounting lug is the same on both the current cage and the AM2 version, that's about all that is the same. Most current basic designs connect with the center lug and have push down cam locks that lock onto the extra lug near the cage corners. There are no extra lugs on the new AM2 cage, so designs that require cam locking won't work. Neither will most of the "step-up" 3 lug mounting clips. AM2 only has one lug per side, and the 3-lug clip is normally intruding on the new screw locations (just a little too wide) to mount on the new AM2 cage.

In addition the current high-end designs, which replace the existing cage with a new mounting system just simply won't work. The current Athlon 64 design uses one screw on each side in the center of the mounting lug. The new AM2 design uses four corner mounted screws - more secure but not useful for mounting current 2 screw mounting schemes.

Current Athlon 64 heatsinks that use a single lug for mounting and no cam for locking will likely work on the new AM2 cage. Recently shipped AMD retail heatsinks have a single lug connection and a lever lock without the locking cam. Those should work fine on the new AM2. However, not a single third party HSF in our lab - the kinds our readers most likley use - would mount properly on the 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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