DDR2 Roundup: Reaching for 667 and Beyond

Specifications: DDR2 Memory

Considering the delays and false starts with DDR2, we were surprised to receive DDR2 modules from 8 different manufacturers for our first DDR2 roundup. The DDR2 from Corsair was even rated at DDR2 667, which caused us to believe that the Corsair would stand head and shoulders above the crowd. We also know of other DDR2 667 samples that are on the way from OCZ and others that will soon be announced. For memory that was barely working a couple of months ago, it certainly appears that DDR2 is maturing much faster than anyone expected.

The 8 DDR2 memories that we received were all rated at or near the Jedec standard for PC2-4300 of 4-4-4-12 timings. Jedec standards for PC2-5300 (DDR2 667) call for 5-5-5 timings, but our Corsair DDR2 667 was rated at the faster 4-4-4, at 667, which already shows improving timings for DDR2.

Memory	Number of DIMMs & Banks	DIMM Size Total Memory	Rated Speed SPD Timings	Rated Voltage
Corsair XMS2 5300 PRO	2 DS	512MB 1GB	DDR2-667 4-4-4-12	1.8V
Crucial PC2-4300U	2 DS	512MB 1GB	DDR2-533 4-4-4-12	1.8V
Geil PC2-4300	2 SS	512MB 1GB	DDR2-533 4-4-4-11	1.8V
Kingmax DDR2-533	2 SS	256MB 512MB	DDR2-533 4-4-4-12	1.8V
Kingston PC2-4300 Value RAM	2 SS	512MB 1GB	DDR2-533 4-4-4-12	1.8V
Micron PC2-4300U	2 DS	512MB 1GB	DDR2-533 4-4-4-12	1.8V
Mushkin DDR2 533	2 SS	512MB 1GB	DDR2-533 4-4-4-12	1.8V
OCZ Premier PC2 4300	2 SS	512MB 1GB	DDR2-533 4-4-4-11	1.8V

The SPD timings were closely bunched around the 4-4-4 Jedec standard, and all the tested memory was rated at the standard DDR2 voltage of 1.8V. Unlike the standardized DDR memory, we received a mixed bag of single- and double-sided memory, even in the same memory capacity. Memory based on Micron chips, like the Micron, Crucial, and Kingmax, were rated 256MB single-sided and 512MB double-sided. Those based on Samsung, like the OCZ Premier, or Elpida, like the Kingston Value RAM, were 512MB single-sided. Double-sided 1GB modules based on these memory chips are therefore likely to appear in the very near future.

We also received 1GB DDR2 memory modules from OCZ, but these early samples were based on Samsung chips. OCZ has decided recently that Elpida chips will be used for their 1GB DDR2 modules, so we eliminated the 1GB DIMMs from our roundup, since they are not representative of production DDR2. While 1GB modules have remained rare and expensive in DDR memory, you will likely find 1GB memory widely available from many DDR2 manufacturers in the very near future. Several manufacturers also plan to introduce 2GB DIMMs in DDR2.

Another difference in DDR2 compared to DDR is the last memory timing number, or tRAS. As we have demonstrated in our DDR reviews, Intel 875/865 chipsets have performed best at the fastest tRAS settings that could be used on the motherboards. This was normally a tRAS value of 5 or 6. DDR2, on the other hand, has a specified tRAS of 11 or 12 in most cases. Does tRAS matter on DDR2 or have the performance rules changed with DDR2 memory timings?