DDR2 Memory Shootout :: Introduction

01-10-2005 · Category: Hardware - Memory

By John Chen

As much as enthusiasts loathe the "slow" performance of DDR2 over standard DDR, nothing can stop DDR2 from taking over. Why do I say this? The reason is that DDR is coming to an end. Following the JEDEC standard, DDR can no longer scale any further in terms of non-overclocked frequency. The fastest chip was 5ns until Samsung released the TCCD that runs at 4ns. Although Samsung was able to advance further, DDR is reaching the light at the end of the tunnel. DDR2 is going to take over and has the ability to scale frequencies to outrageously high levels. Right off the bat, DDR2's first announced frequency runs at 266MHz, which translates to PC2-4200. You'd have to buy overclocked memory in order for RAM to run at 266MHz. Next stop, companies found DDR2 to be capable of running PC2-5400 speeds without a problem.

Before I go any further with our memory contenders, I must explain a little about the difference between DDR2 and DDR. The ideal latencies for DDR memory run at 2-2-2-6 at 200MHz. The ideal latencies for DDR2 run at 4-4-4-12 at 266MHz. Why 266MHz? With Intel's Alderwood and Grantsdale chipsets, using DDR2 and running 200FSB with a DDR533 (3:4 ratio) divider would result in a memory speed of 266MHz. Of course there is no point in running at DDR400 (1:1 ratio) divider simply because DDR2's latencies are already high; you would want to have high frequencies to make up for the high latencies. Other than the high latencies and ability to scale high at high frequencies, there is a one more major difference between DDR2 and DDR. DDR2 carries twice the data back and forth than that of DDR.

So while DDR2 has twice the latencies of DDR, the data carried is twice of that as well, making DDR and DDR2 perform theoretically at the same level. Through many reviews and articles around the web, many enthusiasts argue that DDR provides better performance due to the lower latencies. This is indeed true since most of the benchmarks are written to handle low amounts of data accessing. Games are the perfect examples since the data files are so small that they barely take up a small percentage of the actual amount of memory available. Since most enthusiasts build systems for gaming purposes, they'll want to go with DDR. There are physical differences between DDR2 and DDR memory as well. DDR2 has a 240-pin count as opposed to the 184-pin DDR. DDR2 only uses BGA (Ball Grid Array) memory chips and only needs 1.8v for voltage, as opposed to the TSOP and 2.5v standard of DDR. So what's so good about DDR2?

As mentioned earlier, DDR2 is the next step in memory frequency scaling. The same concept can be applied to Intel's Prescott and Northwood CPU cores. The Northwood was indeed the better core since it allowed great performance, high overclocking potential, and ran at noticeably cooler temperatures; but it was forced to be replaced by the Prescott core. The 0.13 micron construction hit the ceiling. It was unable to go beyond the limit of 3.4GHZ. The smaller 90nm Prescott core allowed extra room for gigahertz speed but came with the mind boggling hot temperatures. There were no other options. You can only count on cooling companies to provide better cooling solutions. The same is with DDR2. The high scaling DDR2 can only count on memory manufacturers to help bring down the high latencies to attract more attention. Personally, I find DDR2 to be a great next step, but demand is low because enthusiasts are automatically turned down by the high latencies.

Our last memory roundup only consisted of 4 contenders. Today's DDR2 memory roundup consists of 6 contenders. Corsair, Crucial, Kingston, PQI, Mushkin, and Centon were all happy to participate. All these companies have DDR2 that run around the same latencies and frequencies, so it comes down to which overclocks the best and which costs the least. Just who will win?