OCZ 3500EB: The Importance of Balanced Memory Timingsby Wesley Fink on April 7, 2004 12:04 AM EST
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Conventional wisdom in the memory industry in recent years has been that CAS latency was the most important specification in memory performance. This has spawned a whole group of high-end DDR products with acronyms like "LL" for Low-Latency, "EL" for Enhanced Latency, and other labels with the message that Latency was the lowest possible and performance was the highest that you could buy. This whole thinking reached a frenzy in the DDR market around DDR333 to DDR400 where the message became so pervasive that if a memory was not CAS 2, then it was not the best performance that you could get.
As DDR memory frequencies have soared beyond DDR400 to DDR500, DDR550, and even higher, we have seen memory modules appear with timings of 3-4-4 at these higher memory speeds. Since customers were now firmly indoctrinated into the CAS 2 camp, many Enthusiasts complained that the new high-speed memory was only half there because what they really wanted was DDR500 at 2-2-2 timings. Variations on this theme were the "proof" that DDR400 run at 5:4 ratio at CAS 2 could normally meet or beat performance of higher speed DDR500 memory, which used slower CAS 3 timings. The point that was forgotten in this argument was that with all things being equal, DDR500 would always perform faster than DDR400, but technology was not to a point where DDR500 CAS 2 memory could be manufactured. This further reinforced for some the almighty importance of CAS latency.
Several recent developments have caused memory manufacturers to re-examine the importance of CAS latency to performance. First, manufacturers have been unable to produce a DDR500 memory that could run at CAS 2. In fact, the DDR500 modules have not even been able to run also at DDR400 at 2-2-2 timings. Second, Winbond announced their exit from the market, removing DDR400 2-2-2 and even 2-2-3 timings from currently available memory. Third, the development of DDR2 memory, which at DDR533 is being launched with 4-4-4 to 5-5-5 timings. An interesting development with DDR2 is that while memory timings are even slower than the worst DDR timings, the performance can sometimes keep up with DDR because of other internal memory timings. This is not praise for DDR2, but all these developments bring to the forefront that CAS Latency is not the only thing that matters in memory performance, and in fact, it may not even be the most important specification as we move to faster memory.
Into this climate, OCZ has introduced their latest EB, or Enhanced Bandwidth, memory with the claim that CAS 2.5 or 3 can often perform just as well as CAS 2. According to Dr. Michael Schuette of OCZ, "Enhanced Bandwidth technology is an exciting improvement that, at 2.5-2-3 (CL-tRP-tRCD) latencies, allows most applications to use data bandwidth that is the same as that delivered by CL-2 modules." Many of you already know Dr. Michael Schuette from his well-respected Lost Circuits technical website. What you may not know is that Michael is now Director of Technology Development for OCZ.