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High Performance DDR DIMMs
Ups and Downs or "how do I keep my stick happy?"
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(Review by MS, July 17, 2001)
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128 MByte DDR DIMM performance
Whoever read the first few pages should be aware that it is relatively easy to achieve good CAS performance on a DDR part whereas tRCD can put a serious limitation on the overclocking capabilities of the DIMMs. In addition the PCB quality has a strong impact on the ability to run at 1T Command rate. Also, as mentioned, the results obtained on either the ASUS CUV266 or the EPoX 8KHA were identical within about 1 MHz, the same holds for Expendable and the hardware-based Ultra-X RAM Stress Test -Pro.
First, let's take a look at the performance of all 128 MByte DIMMs at 2:2:2 / 1T (CMD) setting:
Included are also some Micron PC1600 DIMMs. Please note that the Mosel-Vitelic DIMM was a single prototype assembled with alpha silicon before the chips were even analyzed and tweaked for higher performance. It turns out that there is quite a spread between the individual DIMMs. Also, it is necessary to mention that, by now, Nanya only produces one chip. The "S" in the Taiwan-based DIMM denoted a special speed screening that was lately abandoned because of better yields at the high speed bins.
tRCD=3
Now, let's see what happens if we increase tRCD to 3 cycles without changing anything else.
This is quite stunning, for example the Corsair PC2100 (Samsung-based) DIMMs all of a sudden make it from 148 MHz to 160 MHz, a comparable increase is seen with the original Micron PC2100 DIMM. Bottom line is that almost all DIMMs show much better overclocking potential but as shown earlier, there is a performance penalty associated with higher tRCD latency.
All settings maxxed
Finally, just to be on the safe side, all latencies were set to max, that is, 2.5:3:3 with a 2T CMD rate latency
There is no limit. At 170 MHz, I/O related stability issues essentially killed further exploration of performance. It appears clear that most DIMMs would clock way beyond this "sound barrier".
(*1) Mosel-Vitelic Alpha Silicon untested preproduction chips. The production version will have substantially better performance.
next page: => 256 MB DIMM performance =>
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