From time to time you may see either myself, Anand, or one of the other writers post our thoughts on topics in the forums and news articles. Today, we are going to post a bit of "extended coverage" on our thoughts concerning DDR2. Hopefully, you enjoy our new approach and we encourage you to post your comments!

Even before Computex 2003 we began to first hear some of the upcoming strategies incorporating DDR2 into upcoming Intel platforms.  Several months later, in January, we received confirmation on how and when these technologies were going to appear in upcoming chipsets. 

Today Micron, Elpida and Samsung compose of the majority of the DDR2 market.  Unfortunately there is a lot of confusion about the JEDEC specification.  DDR2 is nearly identical to DDR1, with a few optimizations.  The major optimizations include:

  • 4-bit prefetch (up from 2-bit)
  • Enhanced Registers
  • Additive latency
  • FBGA Packaging
  • On Die Termination
  • DDR2 gets the majority of its punch from the 4 bit prefetch.  DDR2 can effectively write/read four times the amount of data per clock cycle to/from the memory array.  This effectively doubles the data bus speed while keeping the internal bus speed the same from DDR1.  Both DDR1 and DDR2 use a 64-bit interface.

    These optimizations come with the advantage of a slightly lower operating voltage, but requires 240 pins rather than the 184 pins required by DDR today.

    With the talk of different bit prefetches, it becomes difficult to tell the actual clocks of the new memory. Briefly stated, DDR2 runs with a lower internal clock than DDR1. However, since the prefetch is larger than DDR1, the external clock is doubled. For example, if we could run the same DDR400 on the shelves today with DDR2's 4-bit prefetch, it would essentially operate at DDR800. Since this is not possible, the internal bus of the DDR2 modules we see now has been lowered to 100MHz for DDR2-400 and 133MHz for DDR2-533. DDR400 and DDR2-400 should perform the same.

    What does this mean for early adopters?  Essentially; nothing. There will not be a performance increase between DDR2-400 and DDR-400 (or even between DDR2-533 and DDR-533).  DDR2 is the technology to enable post-DDR533 speeds, rather than a technology to enhance it. As we start to see benchmarks of DDR1 versus DDR2 trickle in, consider the maturity of the two technologies.  DDR1 is nearly 5 years old with dozens of chipset manufacturers and billions of dollars in financial backing.  DDR2 still has not even entered full production yet.

    DDR2, today, is still not the DDR2 we will see in mass production come April or May.  Not surprising, Intel has pushed its sample 925X chipsets back another couple weeks to cope with compatibility and performance issues on DDR2.  So, even though PC2-4300 does not perform as well as PC-4300 right now, keep in mind the memory controllers still have some significant changes to undergo.  The timings on today's PC2-4300 are also very poor; most Micron based DDR2 is rated as 4-4-4. Regardless, we should not be looking for performance leaps between DDR2 and DDR1 until memory gets up into the DDR2-667 and DDR2-800 ranges.  According to Intel, VIA and SiS roadmaps, we might see all of these speeds this year.

    With DDR2 memory fixed around $900 for 512MB right now, it is probably unlikely that we will see the enormous rush to Intel's 925X chipset.  Even once prices fall to within range of the DDR prices of today, the newer technology will not really benefit the consumer until we get into the speeds unobtainable by DDR1. 

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    • epiv - Wednesday, February 25, 2004 - link

      Actually have been waiting for PCI Express for sometime. PCI does not provide enough bandwidth for all the PCI cards I have installed. PCI Express will be able to provide the bandwidth I need. Reply
    • retrospooty - Wednesday, February 25, 2004 - link

      With the (at first) expensive DRR2 that, for the time being offers no performance improvement... And the Prescott that offers no performance improvement.. And the PCI express chipset that offers no performance improvement. I think Intel Sales are going to seriously lose way to AMD this year.

      Think about it... To go with the latest Intel i925x chipset, to be released soon, you have to buy...
      1. New i925x motherboard
      2. New Socket 775 Prescott CPU
      3. New PCI Express Video card
      4. DDR2 memory.

      All this will give you no performance advantage over the current offerings. Of course, I realize that later on, maybe next year the Prescott may hit >4ghz, DDR2 may hit 667 mhz, and PCIx will have newer PCIx chips, but for 2004, its not looking too good.

      I'm thinking Socket 939 A64 pretty heavily now.
      Reply
    • mikecel79 - Wednesday, February 25, 2004 - link

      "Does this seem like new technology just for the sake of new technology?"

      DDR1 is at the end of it's life. It's getting very difficult to make it any faster than it is now with good timings. DDR2 is in it's infancy and will scale to much higher speeds than DDR1 will.

      The same thing could be said when DDR memory came out over SDRAM. At first it was not much faster than normal SDRAM but in time it scales much higher than SDRAM.
      Reply
    • shiftomnimega - Wednesday, February 25, 2004 - link

      Does this seem like new technology just for the sake of new technology?

      I mean most people are saying, "Duh," but if there is no improvement over regular DDR right now then who cares about this and who is going to buy it?

      At least Athlon 64 had performance increases in 32-bit land.
      Reply
    • buleyb - Wednesday, February 25, 2004 - link

      I'm always happy to see new tech make it to the mainstream, but 240 pins? Man, laying traces for those DIMM slots must suck. This is the reason serial ram will come about soon enough. Reply

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