Painfully Backwards Compatible

AMD’s big selling point of its Socket-AM3 processors is that they can still be used in Socket-AM2+ motherboards. In other words, you can use them in DDR3 or DDR2 motherboards. There’s a catch - the Phenom II X4 955 needs a BIOS update to work properly. And guess what? Not all motherboards have that BIOS support yet.

It’s not a major change but the fact of the matter is that AMD and its board partners have not done the work necessary to enable support across the board at launch. That means that if you have a Socket-AM2+ board, you may not be able to run the Phenom II X4 955 just yet.


I ran into this problem with my AM2+ testbed. For the past couple of AMD reviews I’ve used MSI’s DKA790GX Platinum, a 790GX based motherboard. AMD actually sent me the board with my first Phenom II X4 940. Unfortunately it doesn’t have an updated BIOS, so the 955 only runs at 800MHz and won’t POST at 3.2GHz. Great.

The following AM2+ boards currently have support for the 955:

Motherboard Socket Chipset BIOS Version
ASUS M3A79-T Deluxe AM2+ AMD 790FX 20090330 0803
DFI Lanparty DK 790FXB-M2RSH AM2+ AMD 790FX 200900327*
ASUS M3A 78-T AM2+ AMD 790GX 20090401 0903
Gigabyte MA790GP-DS4H AM2+ AMD 790GX 20090407 F4*
*These boards still have some known issues with the Phenom II X4 955


And more are coming. AMD suggests that you look at its Motherboard Compatibility page before you pull the trigger if you’re looking to put one of these chips into an older board.


Even Socket-AM3 boards will need a BIOS update but those seem a bit more ready to go. Unfortunately because of all of this board switching, some of my 955 numbers aren’t exactly comparable to my older 940 numbers. I’m using different motherboards (Socket-AM3 vs. AM2+) and different memory (DDR3-1333 vs. DDR2-1066). The numbers are close enough, but there were a couple of situations where performance scaled more than it should have or went negative.

Overall it’s not a huge deal but it’s frustrating for anyone looking to save money and upgrade to the 955 but using an older motherboard.

Index The Move to DDR3: You Can Do It


View All Comments

  • Procurion - Thursday, April 23, 2009 - link

    Cool. My next question would be to wonder why it didn't kick in for the other tests? I guess it wasn't enabled for them? Looks good overall. Reply
  • JarredWalton - Thursday, April 23, 2009 - link

    See page 4 - Turbo mode tends to activate pretty much any time a load is on the CPU. But it's not really "unfair" as all i7 users get that benefit without doing anything extra, plus i7 chips still overclock far beyond that point. Reply
  • ChemicalAffinity - Thursday, April 23, 2009 - link

    Best post ever. Reply
  • whatthehey - Thursday, April 23, 2009 - link

    Congratulations on the cryptic post... or is that pointless post? I'm guessing you're suggesting that the words listed were used with two different companies - AMD and Intel - but if so they certainly weren't used in this article in any way I can see. Care to enlighten the rest of us on the point of your comment?

    Some people are too clever for their own good; others merely think they're clever. Guess which one you are.
  • Lokinhow - Thursday, April 23, 2009 - link

    Oh man, I thinking about the OC
    3.9GHz on Vista x64
    4.2GHz on Vista x86

    Why it happens?
    Does the results are the same using XP x86/x64 and Windows 7 x86/x64?

    That would be interesting to see if it is possible to reach 4.2GHz on Windows 7 x64
  • Griswold - Thursday, April 23, 2009 - link

    Dont hold your breath. Theres more registers (etc) in use under a 64bit OS than a 32bit one. Its highly unlikely that there will be any difference on the exact same hardware. And even if there is a difference between xp/vista/7, 32bit 7 will outdo 64bit 7 as well. 64bit was never the ideal choice for overclocking records...
  • Spoelie - Thursday, April 23, 2009 - link

    In the CS4 test, given the large increase in performance when just going from DDR2 to DDR3, would a faster NB clock (2->2.6/2.8ghz) and faster than DDR1333 memory, while keeping the core at default clock, level the playing field with the core2 processors?

    Seems that in this particular test the phenom is starved for data.
  • duploxxx - Thursday, April 23, 2009 - link

    why do you use these 1GB dimm's in ddr3 config? I would assume you have more oc issues with 4 dimms in stead off 2 dimms?

    G.Skill DDR2-800 2 x 2GB (4-4-4-12)
    G.Skill DDR2-1066 2 x 2GB (5-5-5-15)
    Qimonda DDR3-1066 4 x 1GB (7-7-7-20)
    Corsair DDR3-1333 4 x 1GB (7-7-7-20)
  • Holly - Thursday, April 23, 2009 - link

    Nice article :-)

    btw... last paragraph on the first page... "faster than the Core 2 Duo Q9550." should say "faster than the Core 2 Quad Q9550."
  • ibm386 - Sunday, June 27, 2010 - link

    Intel and Amd are owned by the same person. Since a person can't have monoply in U.S. It has been divided into two different names and obviously diff. CEOs.


Log in

Don't have an account? Sign up now