1GB DIMMs: FAST 2GB DDR Kits from Corsair, Gigaram, and OCZ

Impact of Athlon 64 Memory Controllers on 1GB DIMM Performance

While there has been a lot of talk about the different capabilities of the evolving Athlon 64 on-processor memory controllers, there really hasn't been much discussion of the limitations of some of the earlier Clawhammer controllers. We ran into this issue head-on in our first efforts at testing these 1GB DIMMs.

Most are aware that the early Clawhammer controllers did not officially support 4 DIMMs of any kind at other than a 2T Command Rate. In fact, this continued on in the current Rev. E controller. Some are also aware that the Clawhammer memory controller did not officially support DDR400 with 4 DS DIMMs - official support was DDR333. However, most board makers found that the controller really had no problem with 4DS DIMMs running at DDR400 and supported that "extended feature" in BIOS.

There are not the only differences in the memory controllers that come into play with the more demanding 1GB DIMMs. Our standard test bed CPU has been the 4000+, specifically the original Clawhammer version. Today, you can also buy a 90nm Rev. E version, but we had found no reason to upgrade from the Clawhammer version - until these 1GB tests. Our first efforts with the OCZ 2GB kit saw things very much out of the ordinary in our memory testing. First, Super Pi was no longer a reliable indicator of top speed. In the past, we could run Super Pi, and if it ran, we were confident that the rest of our memory test suite would run without problems.

Now, with the 1GB DIMMs and Clawhammer controller, Super Pi could run perfectly at a CPU clock some 15 points higher than what we could get Quake3, or Return to Wolfenstein to run. With 1GB DIMMs, gaming was now the most demanding task in our suite.

The other strange behavior with our Clawhammer was overclocking. Our first efforts with the OCZ 1GB DIMMs topped out at DDR520. That seemed OK until we saw others doing 540 and even higher on simple air cooling with the same memory. What was different? We finally realized that the highest overclockers with 1GB DIMMs were using processors with Rev. E memory controllers.

Once we switched to an FX57, with a set multiplier of 12X to produce comparable results to past memory reviews, our overclocking clock frequency went up to DDR550 - 30 points higher. The Super Pi issue remained, since we could run Super Pi and Sandra Memory tests all day at DDR565, but gaming tests crashed the system at any setting over DDR550.

It is clear that 1GB DIMMs put a much greater demand on system resources than 512MB DIMMs. It is also clear that the newer Athlon 64 memory controllers are better at meeting the demands of 1GB DIMMs in overclocking. We went back and compared performance of 512MB DIMMs on Clawhammer and Rev. E just for a sanity check. There was virtually no difference in 512MB overclocking on either memory controller - pointing again to the extra demands of 1GB memory modules.

Our advice is to use a recent processor and memory controller with 1GB DIMMs if you plan to overclock the memory. If this is not possible, then expect lower overclocks from your 1GB DIMMs.