OCZ 3500EB: The Importance of Balanced Memory Timings
by Wesley Fink on April 7, 2004 12:04 AM EST- Posted in
- Memory
Enhanced Bandwidth Technology
So, what does OCZ mean by Enhanced Bandwidth? How does it work?Basically, Enhanced Bandwidth (EB) is a means of increasing memory bandwidth by optimizing memory latencies for the best interaction between the memory and the chipset and memory controller. By analyzing memory traffic and benchmark results under varying memory latency settings in the CMOS setup of the BIOS, OCZ claims to have pinpointed the bottlenecks that most affect performance. They further claim that conventional wisdom regarding some memory latencies, namely that the lowest CAS latency yields the best performance, were found to no longer hold true in the higher speed memory of today.
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| Timing diagram for two modules, one running at TRCD-4, CL-2.5, tRP-4 (bottom) and the second with tRCD-3, CL-2.5, tRP-2 (top) showing two consecutive bursts of 8 from two different pages - one of the most common scenarios in real world applications. The effective bandwidth is the ratio between data transfers (black diamonds):NoOps (red arrows). In the case of EB this ratio is 8:7, while without EB it is 8:10, meaning that every transfer of 16 bits is penalized with either 7 or 10 subsequent bus idle cycles. (Clk: clock; Act: row activate command; Rd: read command; Pr: Precharge command, NoOp: No Operation) |
OCZ further explains that their EB series uses low tRP (RAS Precharge, which has a value of 2 in EB) and tRCD (RAS-to-Cas Delay, with a value of 3 in EB) latencies to enhance performance. This is then combined with a Variable Early Read Command to allow for the highest possible effective data bandwidth. Using these optimizations, OCZ says that in most applications, the 2.5-2-3 (CL-tRP-tRCD) will deliver bandwidth that is indistinguishable from CL-2 modules.
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| The effect of issuing an early Read Command on back-to-back transactions of consecutively requested data blocks within the same page. Following one Row Activate Command, three Read commands are given at a CAS Latency of either 2, 2.5 or 3. The colored diamonds are the data transfers that belong to the Read Command in the same color. The graph shows that the net effect of increasing the CAS latency is a single cycle delay within a string of (in this case) 12 consecutive transfers, but no degradation of bandwidth. The double-arrows indicate the CAS latency which is amended by moving the read command further to the left (relative to the end of the previous burst). (Clk: clock; Act: row activate command; Rd: read command; Pr: Precharge command, CL: CAS Latency) |
OCZ says that they have redesigned their memory products using these findings to deliver the highest possible bandwidth to any computer system, and they call these new products EB or Enhanced Bandwidth.
A more technical explanation is beyond the scope of this memory review, but those of you who would like more information on the theories behind Enhanced Bandwidth should take a look at the OCZ Enhanced Bandwidth white paper.
Is OCZ correct: can memory timings of 2.5-2-3 perform just as well as CAS 2 in many applications? Our goal is to find out.
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Pumpkinierre - Wednesday, April 7, 2004 - link
Yeah well I have had OCZ platinum 3200 o'clocked to 3500 (2-2-3-7) for 9months now and noticed it slowly degrading. I used to pass Memtest86 at 220MHz with Game Accelerator (GAT) F1 (Abit IC7-G) but now I have to switch off the GAT at 216MHz to successfully run Memtest86. At F1, DDR Voltage is 2.7V otherwise 2.6V. I notice the mem. modules are quite warm (even hot) so maybe I need extra cooling as the DIMMS are out of the normal air circulation at the top of the case. And its been a hot summer.It seems crazy that memory modules that are at least 12 months old (BH5/BH6) are still the best performers in the 400 to 433MHz range and even higher (original OCZ3700 gold) given the very fast ascent from 266 to 400 at low latencies. Lets hope these Hynix DDR550 modules cut the mustard.
I cant run F1 higher than CAS2 at present (and Street Racer not at all) although others in posts say they do. So finally Wesley, will the EB technology modules run F1 or Street Racer at 466-500Mhz.
johnsonx - Wednesday, April 7, 2004 - link
It might have been interesting to set CAS latency on the other modules to 2.5 to see how much this 'EB' helps vs. non-EB ram at identical timings.This article also simply seems to show (again) that OCZ memory, of any sort, is just plain good. Recall the article on the FX-53, wherein the 2.4Ghz chip with OCZ ram performed more than 200Mhz better than the 2.2Ghz FX-51 with Mushkin RAM... this even though the Mushkin had better timings.
Were I shopping for high performance RAM, my shopping would begin and end with OCZ... it'd just be a matter of choosing which OCZ modules.
Cybercat - Wednesday, April 7, 2004 - link
Well....this is new....and impressive.