The AMD Memory Roadmap: DDR3, FBD and G3MX Examined

With today's announcement we can finally talk about AMD's memory roadmap; the two questions we often hear are: when is AMD planning on moving to DDR3 and what about Fully Buffered DIMM? Both are answered with today's disclosure.

AMD will begin the DDR3 transition on the desktop in the second half of 2008 with its Shanghai processor, but AMD won't fully move to DDR3 until 2009 with Bulldozer. The DDR3 transition beginning with Shanghai and completing with Bulldozer is very similar to the cautious approach AMD took to DDR2 adoption. By the time 2009 rolls around, DDR3 should be very cost competitive with DDR2 and the transition should be seamless.

Despite rumors to the contrary, Bulldozer won't support Intel's Fully Buffered DIMM standard, and instead will use what AMD is calling the "G3 Memory Extender" (G3MX).

FBD addresses the problem of not being able to maintain memory frequency while increasing the number of memory sockets on a motherboard, something that impacts the high end server market. The FBD solution is to serialize the memory bus by placing a buffer chip on each memory module that communicates with the memory controller and memory devices. The memory controller only needs to worry about driving data to these buffers, and the buffers deal with getting data in/out of the memory devices.

While FBD supports up to 8 DIMMs per memory channel, there are three major drawbacks: 1) higher cost per module, 2) higher latencies due to serialization and 3) higher power consumption. AMD has said that it evaluates new memory technologies at each generation, and although it won't rule out FBD for future products, it simply doesn't make sense today.

G3MX addresses the same issue of maintaining memory performance while driving up the number of slots per channel in a more economical manner. The technology simply calls for custom, ASIC-class, buffer logic to be placed on the motherboard itself between the memory controller (in this case the CPU) and the memory slots. There is no conversion of memory interface and thus performance/power shouldn't be impacted nearly as much as FBD, and the big upside is that you can use standard DDR3 memory in the sockets since G3MX is implemented at a motherboard level.

The downside is that with G3MX you are still dealing with a parallel memory interface, which becomes difficult to implement at higher speeds and loads. AMD insists that it can work around any issues related to motherboard design and trace routing, and that G3MX is presently a better solution than FBD for its needs.

The first G3MX implementation will arrive with Bulldozer in 2009; like FBD, it will be limited to high end server/workstation platforms.

Codename Mania Bulldozer Performance Expectations


View All Comments

  • Lord Evermore - Sunday, July 29, 2007 - link

    What the heck are RDDR and UDDR? My only guess is the U might stand for the UMA design, but I don't know if that would be preferred for the server or workstation. Reply
  • Anand Lal Shimpi - Tuesday, July 31, 2007 - link

    RDDR = Registered DDR
    UDDR = Unbuffered DDR

    Take care,
  • Martimus - Thursday, August 02, 2007 - link

    Ok, what is OoO? I couldn't find it with a search on Google. Reply
  • Spartan Niner - Saturday, August 04, 2007 - link

    OoO is "out-of-order" referring to OoOE, "out-of-order-execution"">
  • Martimus - Monday, August 06, 2007 - link

    Thanks. Reply
  • xpose - Saturday, July 28, 2007 - link

    This is the best future roadmap article I have ever read. I am actually excited. No really. Reply
  • najames - Friday, July 27, 2007 - link

    I am an AMD fanboy, of 7 computers I have at home, only the 5 year old laptop has an Intel chip now. Dual cores are actually likely all I REALLY need. That said, I am sick of a bunch of hype and no new products. It's all blow and no show. I don't care about years down the road because it could all change between now and then.

    AMD/ATI could be a good thing too if they make good, polished drivers, 100% working for what was promised. How about throwing people a bone to make them switch, maybe even make some kick butt Linux drivers too.

    We were all on an AMD bus and nobody has been driving since the X2 chip. They taunted Intel and handed out huge bonuses, but forgot about any new development. I have to credit Intel, they kicked butt with Core 2, and seem to be doing more butt kicking going forward.

    I watched Hector on CNBC last night and he didn't look like he had a clue what was going on. Granted they weren't asking him details of any processors, but he was dodging basic business questions. Why do I have several hundred shares of AMD?
  • Regs - Monday, July 30, 2007 - link


    Why do I have several hundred shares of AMD?

    Because those relatively cheap shares, compared to Intel's, might be worth hundreds of times more one day from that stuff you call blow. Blow = prospects in business terms.

    I would say the same thing as you did though at first. It's obvious AMD and ATi's pipeline dried up and unfortunately both consecutively. You can argue that the 2900XT is a good card, performs well, etc..etc.. but that doesn't explain why AMD offers crapware for main stream (where the real money is). As for AMD's CPU line can only sell old for so long in the technology sector without taking a hit.
  • kilkennycat - Friday, July 27, 2007 - link

    .... dump ATi. The marriage made in hell. New products unable to meet schedule and with inferior performance, thus no way of rapidly recovering development costs by pricing for performance.

    Dave Orton sure did a neat sell-job on AMD, walking away with $$millions when AMD paid a 20% premium for a chronically non-performing company barely managing to eke out some tiny profits during the last couple of years. No wonder Mr. Orton was finally shown the door.
  • kleinwl - Friday, July 27, 2007 - link

    What is the problem with AMD, did they not receive enough feedback that UVD is a "must have" on high end units. I don't want to have choose between good gaming performance and movie performance... I am paying a ridiculous premium already for hardware... the least they could do is make sure it has all the bells and whistles. Reply

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